Meet the Ocotillo

I love the ocotillo (Fouquieria splendens) for many reasons. It is an impossible plant to miss with its spindly, spine-covered stems. It is a lovely plant that is right at home in the arid parts of southwestern North America. Beyond its unique appearance, the ocotillo is a fascinating and important component of the ecology of this region.

My first impression of ocotillo was interesting. I could not figure out where this plant belonged on the tree of life. As a temperate northeasterner, one can forgive my taxonomic ignorance of this group. The family from which it hails, Fouquieriaceae, is restricted to southwestern North America. It contains one genus (Fouquieria) and about 11 species, all of which are rather spiky in appearance.

Of course, those spines serve as protection. Resources like water are in short supply in desert ecosystems so these plants ensure that it is a real struggle for any animal looking to take a bite to get at the sap inside. Those spines are tough as well. One manged to pierce the underside of my boot during a hike and I was lucky that it just barely grazed the underside of my foot. Needless to say, the ocotillo is a plant worthy of attention and respect.

One of the most striking aspects of ocotillo life is how quickly these plants respond to water. As spring brings rain to this region of North America, ocotillo respond with wonderful sprays of bright red flowers situated atop their spindly stems. These blooms are usually timed so as to take advantage of migrating hummingbirds and emerging bees. The collective display of a landscape full of blooming ocotillo is jaw-droppingly gorgeous and a sight one doesn't soon forget. It is as if the whole landscape has suddenly caught on fire. Indeed, the word "ocotillo" is Spanish for "little torch."

Flowering isn't the only way this species responds to the sudden availability of water. A soaking rain will also bring about an eruption of leaves, turning its barren, white stems bright green. The leaves themselves are small and rather fragile. They do not have the tough, succulent texture of what one would expect out of a desert specialist. That is because they don't have to ride out the hard times. Instead, ocotillo are what we call a drought deciduous species, producing leaves when times are good and water is in high supply, and dropping them as soon as the soil dries out.

This cycle of growing and dropping leaves can and does happen multiple times per year. It is not uncommon to see ocotillo leaf out up to 4 or 5 times between spring and fall. During the rest of the year, ocotillo relies on chlorophyll in its stems for its photosynthetic needs. Interestingly enough, this poses a bit of a challenge when it comes to getting enough CO2. Whereas leaves are covered in tiny pours called stomata which help to regulate gas exchange, the stems of an ocotillo are a lot less porous, making it a challenge to get gases in and out. This is where the efficient metabolism of this plant comes in handy.

All plants undergo respiration like you and me. The carbohydrates made during photosynthesis are broken down to fuel the plant and in doing so, CO2 is produced. Amazingly, the ocotillo (as well as many other plants that undergo stem photosynthesis) are able to recycle the CO2 generated by cellular respiration back into photosynthesis within the stem. In this way, the ocotillo is fully capable of photosynthesis even without leaves.

Through the good times and the bad, the ocotillo and its relatives are important components of desert ecology. They are as hardy as they are beautiful and getting to see them in person has been a remarkable experience. They ad a flare of surreality to the landscape that must be seen in person to believe.

Further Reading: [1] [2] [3] [4] [5]

From Herbivore to Pollinator Thanks to a Parasitoid

In the Atlantic forests of Brazil resides a small orchid known scientifically as Dichaea cogniauxiana. Like most plant species, this orchid experiences plenty of pressure from herbivores. It faces rather intense pressures from two species of weevil in the genus Montella. These weevils are new to science and have yet been given full species status. What's more, they don't appear to eat the leaves of D. cogniauxiana. Instead, female weevils lay eggs in the developing fruits and the larvae hatch out and consume the seeds within. In other words, they treat the fruits like a nursery chamber.

This is where this relationship gets interesting. You see, the weevils themselves appear to take matters into their own hands. Instead of waiting to find already pollinated orchids, an event that can be exceedingly rare in these dense forests, these weevils go about pollinating the orchids themselves. Females have been observed picking up orchid pollinia and depositing the pollen onto the stigmas. In this way, they ensure that there will be developing fruits in which they can raise their young.

Left unchecked, the weevil larvae readily consume all of the developing seeds within the pod, an unfortunate blow to the reproductive efforts of this tiny orchid. However, the situation changes when parasitoid wasps enter the mix. The wasps are also looking for a place to rear their young but the wasp larvae do not eat orchid seeds. Instead, the wasps must find juicy weevil larvae in which to lay their eggs. When the wasp larvae hatch out, they eat the weevil larvae from the inside out and this is where things get really interesting.

The wasp larvae develop at a much faster rate than do the weevil larvae. As such, they kill the weevil long before it has a chance to eat all of the orchid seeds. By doing so, the wasp has effectively rescued the orchids reproductive effort. Over a five year period, researchers based out of the University of Campinas found that orchid fruits in which wasp larvae have killed off the weevil larvae produced nearly as many seeds as uninfected fruits. As such, the parasitoid wasps have made effective pollinators out of otherwise destructive herbivorous weevils.

The fact that a third party (in this case a parasitic wasp) can change a herbivore into an effective pollinator is quite remarkable to say the least. It reminds us just how little we know about the intricate ways in which species interact and form communities. The authors note that even though pollination in this case represents selfing and thus reduced genetic diversity, it nonetheless increases the reproductive success of an orchid that naturally experiences low pollination rates to begin with. In the hyper diverse and competitive world of Brazilian rainforests, even self-pollination cab be a boost for this orchid.

Photo Credits: [1] [2]

Further Reading: [1]

Apocynaceae Ant House

Bullate leaves help the vine clasp to the tree as well as house ant colonies. Photo by Richard Parker licensed under CC BY-NC-SA 2.0

The dogbane family, Apocynaceae, comes in many shapes, sizes, and lifestyles. From the open-field milkweeds we are most familiar with here in North America to the cactus-like Stapeliads of South Africa, it would seem that there is no end to the adaptive abilities of this family. Being an avid gardener both indoors and out, the diversity of Apocynaceae means that I can be surrounded by these plants year round. My endless quest to grow new and interesting houseplants was how I first came to know a genus within the family that I find quite fascinating. Today I would like to briefly introduce you to the Dischidia vines.

The genus Dischidia is native to tropical regions of China. Like its sister genus Hoya, these plants grow as epiphytic vines throughout the canopy of warm, humid forests. Though they are known quite well among those who enjoy collecting horticultural curiosities, Dischidia as a whole is relatively understudied. These odd vines do not attach themselves to trees via spines, adhesive pads, or tendrils. Instead, they utilize their imbricated leaves to grasp the bark of the trunks and branches they live upon.

The odd, bulb-like leaves of the urn vine (Dischidia rafflesiana) Photo by Bernard DUPONT licensed under CC BY-SA 2.0

One thing we do know about this genus is that most species specialize in growing out of arboreal ant nests. Ant gardens, as they are referred to, offer a nutrient rich substrate for a variety of epiphytic plants around the world. What's more, the ants will visciously defend their nests and thus any plants growing within.

The flowers of Dischidia ovata Photo by Krzysztof Ziarnek, Kenraiz licensed under CC BY-SA 4.0

Some species of Dischidia take this relationship with ants to another level. A handful of species including D. rafflesiana, D. complex, D. major, and D. vidalii produce what are called "bullate leaves." These leaves start out like any other leaf but after a while the edges stop growing. This causes the middle of the leaf to swell up like a blister. The edges then curl over and form a hollow chamber with a small entrance hole.

Photo by Krzysztof Ziarnek, Kenraiz licensed under CC BY-SA 4.0

These leaves are ant domatia and ant colonies quickly set up shop within the chambers. This provides ample defense for the plant but the relationship goes a little deeper. The plants produce a series of roots that crisscross the inside of the leaf chamber. As ant detritus builds up inside, the roots begin to extract nutrients. This is highly beneficial for an epiphytic plant as nutrients are often in short supply up in the canopy. In effect, the ants are paying rent in return for a place to live.

Growing these plants can take some time but the payoff is worth. They are fascinating to observe and certainly offer quite a conversation piece as guests marvel at their strange form.

Photo Credits: [1] [2] [3] [4] [5]

Further Reading: [1]

Early Land Plants Made The World Muddy

Cooksonia is one of the earliest land plants to have evolved. Photo by Matteo De Stefano/MUSE licensed under CC BY-SA 3.0

Try to picture the world before life moved onto land. It would have been a vastly different landscape than anything we know today. For one, there would have been no soil. Before life moved onto land, there was nothing organic around to facilitate soil formation. This would have changed as terrestrial habitats were slowly colonized by microbes and eventually plants. A recent paper published in Science is one of the first to demonstrate that the rise in certain sediments on land, specifically mud-forming clays, coincided with the rise in deep-rooted land plants.

This was no small task. The research duo had to look at thousands of reports spanning from the Archean eon, some 3.5 billion years ago, to the Carboniferous period, some 358 million years ago. By looking for the relative amounts of a sedimentary rock called mudrock in terrestrial habitats, they were able to see how the geology of terrestrial habitats was changing through time. What they found was that the presence of mudrock increased by orders of magnitude around the same time as early land plants were beginning to colonize land. Before plants made it onto land, mudrocks comprised a mere 1% of terrestrial sediments. By the end of the Carboniferous period, mudrocks had risen to 26%.

This begs the question, why are mudrocks so significant? What do they tell us about what was going on in terrestrial environments? A key to these questions lies in the composition of mudrocks themselves. Mudrock is made up of fine grained sediments like clay. There are many mechanisms by which clay can be produced and certainly this was going on well before plants made it onto the scene. The difference here is in the quantity of clay-like minerals in these sediments. Whereas bacteria and fungi do facilitate the formation of clay minerals, they do so in small quantities.

A little bit of moss goes a long way for erosion control!

The real change came when plants began rooting themselves into the earth. In pushing their roots down into sediments, plants act as conduits for increased weathering of said minerals. Roots not only increase the connectivity between subsurface geology and the atmosphere, they also secrete substances like organic acids and form symbiotic relationships with cyanobacteria and fungi that accelerate the weather process. No purely tectonic or chemical processes can explain the rate of weathering that must have taken place to see such an increase in these fine grained minerals.

What's more, the presence of rooted plants on land would have ensured that these newly formed muds would have stuck around on the landscape much longer. Whereas in the absence of plants, these sediments would have been washed away into the oceans, plants were suddenly holding onto them. Plant roots act as binders, holding onto soil particles and preventing erosion. Aside from their roots, the rest of these early land plants would have also held onto sediments via a process known as the baffling effect. As water and wind pick up and move sediments, they inevitably become trapped in and around the stems and leaves of plants. Even tiny colonies of liverworts and moss are capable of doing this and entire mats of these would have contributed greatly to not only the formation of these sediments, but their retention as well.

The movement of plants onto land changed the course of history. It was the beginning of massive changes to come and much of that started with the gradual formation of soils. We owe everything to these early botanical pioneers.

Photo Credit: [1]

Further Reading: [1]

The Wild World of the Creosote Bush

Apart from the cacti, the real rockstar of my Sonoran experience was the creosote bush (Larrea tridentata). Despite having been quite familiar with creosote as an ingredient, I admit to complete ignorance of the plant from which it originates. Having no familiarity with the Sonoran Desert ecosystem, I was walking into completely new territory in regard to the flora. It didn’t take long to notice creosote though. Once we hit the outskirts of town, it seemed to be everywhere.

If you are in the Mojave, Sonoran, and Chihuahuan Deserts of western North America, you are never far from a creosote bush. They are medium sized, slow growing shrubs with sprays of compact green leaves, tiny yellow flowers, and fuzzy seeds. Apparently what is thought of as one single species is actually made up of three different genetic populations. The differences between these has everything to do with chromosome counts. Populations in the Mojave Desert have 78 chromosomes, Sonoran populations have 52 chromosomes, and Chihuahuan have 26. This may have to do with the way in which these populations have adapted to the relative amounts of rainfall each of these deserts receive throughout the year, however, it is hard to say for sure.

Regardless, creosote is supremely adapted to these xeric ecosystems. For starters, their branching architecture coupled with their tiny leaves are arranged so as to make the most out of favorable conditions. If you stare at these shrubs long enough, you may notice that their branches largely orient towards the southeast. Also, their leaves tend to be highly clustered along the branches. It is thought that this branching architecture allows the creosote to minimize water loss while maximizing photosynthesis.

Deserts aren’t hot 24 hours per day. Night and mornings are actually quite cool. By taking advantage of the morning sun as it rises in the east, creosote are able to open their stomata and commence photosynthesis during those few hours when evapotranspiration would be at its lowest. In doing so, they are able to minimize water loss to a large degree. Although their southeast orientation causes them to miss out on afternoon and evening sun to a large degree, the benefits of saving precious water far outweigh the loss to photosynthesis. The clustering of the leaves along the branches may also reduce overheating by providing their own shade. Coupled with their small size, this further reduces heat stress and water loss during the hottest parts of the day.

Creosote also secrets lots of waxy, resinous compounds. These coat the leaves and to some extent the stems, making them appear lacquered. It is thought that this also helps save water by reducing water loss through the leaf cuticle. However, the sheer diversity of compounds extracted from these shrubs suggests other functions as well. It is likely that at least some of these compounds are used in defense. One study showed that when desert woodrats eat creosote leaves, the compounds within caused the rats to lose more water through their urine and feces. They also caused a reduction in the amount of energy the rats were able to absorb from food. In other words, any mammal that regularly feeds on creosote runs the risk of both dehydration and starvation. This isn’t the only interesting interaction that creosote as with rodents either. Before we get to that, however, we first need to discuss roots.

Creosote shrubs have deep root systems that are capable of accessing soil water that more shallowly rooted plants cannot. This brings them into competition with neighboring plants in intriguing ways. When rainfall is limited, shallowly rooted species like Opuntia gain access to water before it has a chance to reach deeper creosote roots. Surprisingly this happens more often than you would think. The branching architecture of creosote is such that it tends to accumulate debris as winds blow dust around the desert landscape. As a result, the soils directly beneath creosote often contain elevated nutrients. This coupled with the added shade of the creosote canopy means that seedlings that find themselves under creosote bushes tend to do better than seedlings that germinated elsewhere. As such, creosote are considered nurse plants that actually facilitate the growth and survival of surrounding vegetation. So, if recruitment and resulting competition from vegetation can become such an issue for long term creosote survival, why then do we still so much creosote on the landscape?

The answer may lie in rodents and other burrowing animals in these desert ecosystems. Take a look at the base of a large creosote and you will often find the ground littered with burrows. Indeed, many a mammal finds the rooting zone of the creosote shrub to be a good place to dig a den. When these animals burrow under shallowly rooted desert plants, many of them nibble on and disturb the rooting zones. Over the long-term, this can be extremely detrimental for the survival of shallow rooted species. This is not the case for creosote. Its roots run so deep that most burrowing animals cannot reach them. As such, they avoid most of the damage that other plants experience. This lends to a slight survival advantage for creosote at the expense of neighboring vegetation. In this way, rodents and other burrowing animals may actually help reduce competition for the creosote.

Barring major disturbances, creosote can live a long, long time. In fact, one particular patch of creosote growing in the Mojave Desert is thought to be one of the oldest living organisms on Earth. As creosote shrubs grow, they eventually get to a point in which their main stems break and split. From there, they begin producing new stems that radiate out in a circle from the original plant. These clones can go on growing for centuries. By calculating the average growth rate of these shrubs, experts have estimated that the Mojave specimen, affectionately referred to as the “King Clone,” is somewhere around 11,700 years old!

The ring of creosote that is King Clone.

For creosote, its slow and steady wins the race. They are a backbone of North American desert ecosystems. Their structure offers shelter, their seeds offer food, and their flowers support myriad pollinators. Creosote is one shrub worthy of our respect and admiration.

Photo Credit: [1] [2]

Further Reading: [1] [2] [3] [4]

Palo Verde

One of the first plants I noticed upon arriving in the Sonoran Desert were these small spiny trees without any leaves. The reason they caught my eye was that every inch of them was bright green. It was impossible to miss against the rusty brown tones of the surrounding landscape. It didn’t take long to track down the identity of this tree. What I was looking at was none other than the palo verde (Parkinsonia florida).

Palo verde belong to a small genus of leguminous trees. Parkinsonia consists of roughly 12 species scattered about arid regions of Africa and the Americas. The common name of “palo verde” is Spanish for “green stick.” And green they are! Like I said, every inch of this tree gives off a pleasing green hue. Of course, this is a survival strategy to make the most of life in arid climates.

Despite typically being found growing along creek beds, infrequent rainfall limits their access to regular water supplies. As such, these trees have adapted to preserve as much water as possible. One way they do this is via their deciduous habit. Unlike temperate deciduous trees which drop their leaves in response to the changing of the seasons, palo verde drop their leaves in response to drought. And, as one can expect from a denizen of the desert, drought is the norm. Leaves are also a conduit for moisture to move through the body of a plant. Tiny pours on the surface of the leaf called stomata allow water to evaporate out into the environment, which can be quite costly when water is in short supply.

The tiny pinnate leaves and pointy stems of the palo verde. 

Not having leaves for most of the year would be quite a detriment for most plant species. Leaves, after all, are where most of the photosynthesis takes place. That is, unless, you are talking about a palo verde tree. All of that green coloration in the trunk, stems, and branches is due to chlorophyll. In essence, the entire body of a palo verde is capable of performing photosynthesis. In fact, estimates show that even when the tiny pinnate leaves are produced, a majority of the photosynthetic needs of the tree are met by the green woody tissues.

Flowering occurs whenever there is enough water to support their development, which usually means spring. They are small and bright yellow and a tree can quickly be converted into a lovely yellow puff ball seemingly overnight. Bees relish the flowers and the eventual seeds they produce are a boon for wildlife in need of an energy-rich meal.

However, it isn’t just wildlife that benefits from the presence of these trees. Other plants benefit from their presence as well. As you can probably imagine, germination and seedling survival can be a real challenge in any desert. Heat, sun, and drought exact a punishing toll. As such, any advantage, however slight, can be a boon for recruitment. Research has found that palo verde trees act as important nurse trees for plants like the saguaro cactus (Carnegiea gigantea). Seeds that germinate under the canopy of a palo verde receive just enough shade and moisture from the overstory to get them through their first few years of growth.

In total, palo verde are ecologically important trees wherever they are native. What’s more, their ability to tolerate drought coupled with their wonderful green coloration has made them into a popular tree for native landscaping. It is certainly a tree I won’t forget any time soon.

Further Reading: [1] [2]

The Other Pawpaws

Asimina tetramera Photo by Bob Peterson licensed under CC BY-SA 2.0

The pawpaw (Asimina triloba) has been called "America's forgotten fruit." Once popular among Native Americans and settlers alike, it fell out of the public eye until quite recently. If one considers the pawpaw "forgotten" then its relatives have been straight up ignored. Indeed, the pawpaw shares the North American continent with 10 other Asimina species. 

Asimina angustifolia Photo by Mason Brock

The genus Asimina belongs to a family of plants called the custard apple family - Annonaceae. It is a large family that mostly resides in the tropics. In fact, the genus Asimina is the only group to occur outside of the tropics. Though A. triloba finds itself growing as far north as Canada, the other species within this genus are confined to southeastern North America in coastal plain communities. 

Asimina parviflora Photo by Mason Brock

As I mentioned above, there are 10 other species in the genus and at least one naturally occurring hybrid. For the most part, they all prefer to grow where regular fires keep competing vegetation at bay. They are rather small in stature, usually growing as shrubs or small, spindly trees. They can be pretty inconspicuous until it comes time to flower.

Asimina obovata Photo by Homer Edward Price licensed under CC BY 2.0

The flowers of the various Asimina species are relatively large and range in color from bright white to deep red, though the most common flower color seems to be creamy white. The flowers themselves give off strange odors that have been affectionately likened to fermenting fruit and rotting meat. Of course, these odors attract pollinators. Asimina aren't much of a hit with bees or butterflies. Instead, they are mainly visited by blowflies and beetles. 

As is typical of the family, all of the Asimina produce relatively large fruits chock full of hard seeds. Seed dispersal for the smaller species is generally accomplished through the help of mammals like foxes, coyotes, raccoons, opossums, and even reptiles such as the gopher tortoise. Because the coastal plain of North America is a fire-prone ecosystem, most of the Asimina are well adapted to cope with its presence. In fact, most require it to keep their habitat open and free of too much competition. At least one species, A. tetramera, is considered endangered in large part due to fire sequestration.

Asimina reticulata Photo by Bob Peterson licensed under CC BY-SA 2.0

All of the 11 or so Asimina species are host plants for the zebra swallowtail butterfly (Eurytides marcellus) and the pawpaw sphinx moth (Dolba hyloeus). The specialization of these two insects and few others has to do with the fact that all Asimina produce compounds called acetogenins, which act as insecticides. As such, only a small handful of insects have adapted to be able to tolerate these toxic compounds. 

Asimina tetramera

Sadly, like all other denizens of America's coastal plain forest, habitat destruction is taking its toll on Asimina numbers. As mentioned above, at least one species (A. tetramera) is considered endangered. We desperately need to protect these forest habitats. Please support a local land conservation organization like the Partnership For Southern Forestland Conservation today!

LISTEN TO AN INTERVIEW ALL ABOUT PAWPAW FLOWER SCENTS

See a list of the Asimina of North America here: [1] 

Further Reading: [1] [2] [3] [4] [5]

An Endangered Iris With An Intriguing Pollination Syndrome

The Golan iris (Iris hermona) is a member of the Oncocyclus section, an elite group of 32 Iris species native to the Fertile Crescent region of southwestern Asia. They are some of the showiest irises on the planet. Sadly, like many others in this section, the Golan iris is in real danger of going extinct.

The Golan iris has a rather limited distribution. Despite being named in honor of Mt. Hermon, it is restricted to the Golan Heights region of northern Israel and southwestern Syria. Part of the confusion stems from the fact that the Golan iris has suffered from a bit of taxonomic uncertainty ever since it was discovered. It is similar in appearance to both I. westii and I. bismarckiana with which it is frequently confused. In fact, some authors still consider I. hermona to be a variety of I. bismarckiana. This has led to some serious issues when trying to assess population numbers. Despite the confusion, there are some important anatomical differences between these plants, including the morphology of their rhizomes and the development of their leaves. Regardless, if these plants are in fact different species, it means their respective numbers in the wild decrease dramatically. 

Photo by Dr. Avishai Teicher Pikiwiki Israel licensed under CC BY 2.5

Like other members of the Oncocyclus group, the Golan iris exhibits an intriguing pollination syndrome with a group of bees in the genus Eucera. Their large, showy flowers may look like a boon for pollinators, however, close observation tells a different story. The Golan iris and its relatives receive surprisingly little attention from most of the potential pollinators in this region.

One reason for their lack of popularity has to do with the rewards (or lack thereof) they offer potential visitors. These irises produce no nectar and very little pollen. Because of this and their showy appearance, most pollinators quickly learn that these plants are not worth the effort. Instead, the only insects that ever pay these large blossoms any attention are male Eucerine bees. These bees aren't looking for food or fragrance, however. Instead, they are looking for a place to rest. 

A Eucerine bee visiting a nectar source. Photo by Gideon Pisanty (Gidip) גדעון פיזנטי • CC BY 3.0

The Oncocyclus irises cannot self pollinate, which makes studying potential pollinators a bit easier. During a 5 year period, researchers noted that male Eucerine bees were the only insects that regularly visited the flowers and only after their visits did the plants set seed. The bees would arrive at the flowers around dusk and poke around until they found one to their liking. At that point they would crawl down into the floral tube and would not leave again until morning. The anatomy of the flower is such that the bees inevitably contact stamen and stigma in the process. Their resting behavior is repeated night after night until the end of the flowering season and in this way pollination is achieved. Researchers now believe that the Golan iris and its relatives are pollinated solely by these sleeping male bees.

Sadly, the status of the Golan iris is rather bleak. As recent as the year 2000, there were an estimated 2,000 Golan irises in the wild. Today that number has been reduced to a meager 350 individuals. Though there is no single smoking gun to explain this precipitous decline, climate change, cattle grazing, poaching, and military activity have exacted a serious toll on this species. Plants are especially vulnerable during drought years. Individuals stressed by the lack of water succumb to increased pressure from insects and other pests. Vineyards have seen an uptick in Golan in recent years as well, gobbling up viable habitat in the process.

Photo by Dr. Avishai Teicher Pikiwiki Israel licensed under CC BY 2.5

It is extremely tragic to note that some of the largest remaining populations of Golan irises can be found growing in active mine fields. It would seem that one of the only safe places for these endangered plants to grow are places that are extremely lethal to humans. It would seem that our propensity for violent tribalism has unwittingly led to the preservation of this species for the time being.

At the very least, some work is being done not only to understand what these plants need in order to germinate and survive, but also assess the viability of relocated plants that are threatened by human development. Attempts at transplanting individuals in the past have been met with limited success but thankfully the Oncocyclus irises have caught the eye of bulb growers around the world. By sharing information on the needs of these plants in cultivation, growers can help expand on efforts to save species like the Golan iris.

Photo Credits: [1] [2] [3] [4]

Further Reading: [1] [2] [3] [4]

Parasitic Plant Rediscovered After a 151 Year Absence

Extinction is a hard status to confirm for many types organisms. Whereas discovering a new species requires finding only a single individual, declaring one extinct requires knowing that there are no individuals left at all. This is especially true when organisms live cryptic lifestyles, a point recently made quite apparent by the rediscovery of a small parasitic plant known scientifically ask Thismia neptunis.

Thismia neptunis is a type of parasite called a mycoheterotroph, which means it makes its living by parasitizing mycorrhizal fungi in the soil. It obtains all of its needs in this way. As such, it produces no leaves, no chlorophyll, and really nothing that would readily identify it outright as a plant. All one would ever see of this species are its bizarre flowers that look more like a sea anemone than anything botanical. Like most mycoheterotrophs, when not in flower it lives a subterranean lifestyle.

The original drawing of Thismia neptunis (from Beccari 1878).

This is why finding them can be so difficult. Even when you know where they are supposed to grow, infrequent flowering events can make assessing population numbers extremely difficult. Add to this the fact that Thismia neptunis is only known from a small region of Borneo near Sarawak where it grows in the dense understory of hyperdiverse Dipterocarp forests. It was first found and described back in 1866 but was not seen again for 151 years. To be honest, it is hard to say whether or not most folks were actively searching.

Regardless, after a 151 year absence, a team of botanists recently rediscovered this wonderful little parasite flowering not too far from where it was originally described. Though more study will be needed to flesh out the ecology of this tiny parasitic plant, the team was fortunate enough to witness a few tiny flies flitting around within the flower tube. It could very well be that these odd flowers are pollinated by tiny flies that frequent these shaded forest understories.

As exciting as this rediscovery is, it nonetheless underscores the importance of forest conservation. The fact that no one had seen this plant in over a century speaks volumes about how little we understand the diversity of such biodiverse regions. The rate at which such forests are being cleared means that we are undoubtedly losing countless species that we don't even know exist. Forest conservation is a must. 

Click here to support forest conservation efforts in Borneo. 

Photo Credit and Further Reading: [1]

The Giant Genomes of Geophytes

Canopy plant (Paris japonica) Photo by Radek Szuban licensed under CC BY-NC 2.0

A geophyte is any plant with a short, seasonal lifestyle and some form of underground storage organ ( bulb, tuber, thick rhizome, etc.). Plants hailing from a variety of families fall into this category. However, they share more than just a similar life history. A disproportionate amount of geophytic plants also possess massive genomes. 

As we have discussed in previous posts, life isn't easy for geophytes. Cold temperatures, a short growing season, and plenty of hungry herbivores represent countless hurdles that must be overcome. That is why many geophytes opt for rapid growth as soon as conditions are right. However, they don't do this via rapid cell division. 

Dutchman's breeches (Dicentra cucullaria) emerging with preformed buds.

Instead, geophytes spend the "dormant" months pre-growing all of their organs. What's more, the cells that make up their leaves and flowers are generally much larger than cells found in non-geophytes. This is where that large genome comes into plant. If they had to wait until the first few weeks of spring to start their development, a large genome would only get in the way. Their dormant season growth means that these plants don't have to worry about streamlining the process of cellular division. They can take their time. 

As such, an accumulation of genetic material isn't detrimental. Instead, it may actually be quite beneficial for geophytes. Associated with large genomes are things like larger stomata, which helps these plants better regulate their water needs. The large genomes may very well be the reason that many geophytic plants are so good at taking advantage of such ephemeral growing conditions. 

When the right conditions present themselves, geophytes don't waste time. Pre-formed organs like leaves and flowers simply have to fill with water instead of having to wait for tissues to divide and differentiate. Water is plentiful during the spring so geophytes can rely on turgor pressure within their large cells for stability rather than investing in thick cell walls. That is why so many spring blooming plants feel so fleshy to the touch. 

Taken together, we can see how large genomes and a unique growth strategy have allowed these plants to exploit seasonally available habitats. It is worth noting, however, that this is far from the complete picture. With such a wide variety of plant species adopting a geophytic lifestyle, we still have a lot to learn about the secret lives of these plants.

Photo Credits: [1] [2]

Further Reading: [1]

The Pima Pineapple Cactus

The Pima pineapple cactus (Coryphantha robustispina) is a federally endangered cactus native to the Sonoran Desert. It is a relatively small cactus by most standards, a fact that can make it hard to find even with a trained eye. Sadly, the plight of this cactus is shared by myriad other plant species of this arid region. Urbanization, fire, grazing, and illegal collection are an ever present threat thanks to our insatiable need to gobble up habitat we should never have occupied in the first place. 

Deserts are lands of extremes and the Pima pineapple cactus seems ready for whatever its habitat can throw its way (naturally). Plants are usually found growing individually but older specimens can take on a clustered clonal habit. During the winter months, the Pima pineapple cactus shrivels up and waits until warmth returns. Come spring, the Pima pineapple cactus begins anew. On mature specimens, flower buds begin to develop once the plant senses an increase in daylight. 

Photo by Johnida Dockens licensed under CC BY-NC-ND 2.0

The flower buds continue to develop well into summer but seem to stop after a certain point. Then, with the onset of the summer monsoons, flower buds quickly mature and open all at once. It is thought that this evolved as a means of synchronizing reproductive events among widely spaced populations. You see, seed set in this species is best achieved via cross pollination. With such low numbers and a lot of empty space in between, these cacti must maximize the chances of cross pollination.

If they were to flower asynchronously, the chances of an insect finding its way to two different individuals is low. By flowering together in unison, the chances of cross pollination are greatly increased. No one is quite sure exactly how these cacti manage to coordinate these mass flowering events but one line of reasoning suggests that the onset of the monsoon has something to do with it. It is possible that as plants start to take up much needed water, this triggers the dormant flower buds to kick into high gear and finish their development. More work is needed to say for sure.

Seed dispersal for this species comes in the form of a species of hare called the antelope jackrabbit. Jackrabbits consume Pima fruits and disperse them across the landscape as they hop around. However, seed dispersal is just one part of the reproductive process. In order to germinate and survive, Pima pineapple cacti seeds need to end up in the right kind of habitat. Research has shown that the highest germination and survival rates occur only when there is enough water around to fuel those early months of growth. As such, years of drought can mean years of no reproduction for the Pima.

Taken together, it is no wonder then why the Pima pineapple cactus is in such bad shape. Populations can take years to recover if they even manage to at all. Sadly, humans have altered their habitat to such a degree that serious action will be needed to bring this species back from the brink of extinction. Aside from the usual suspects like habitat fragmentation and destruction, invasive species are playing a considerable role in the loss of Pima populations. 

Lehmann lovegrass (Eragrostis lehmanniana) was introduced to Arizona in the 1930's and it has since spread to cover huge swaths of land. What is most troubling about this grass is that it has significantly altered the fire regime of these desert ecosystems. Whereas there was once very little fuel for fires to burn through, dense stands of Lehmann lovegrass now offer plenty of stuff to burn. Huge, destructive fires can spread across the landscape and the native desert vegetation simply cannot handle the heat. Countless plants are killed by these burns.

Sometimes, if they are lucky, large cacti can resprout following a severe burn, however, all too often they do not. Entire populations can be killed by a single fire. What few plants remain are frequent targets of poaching. Cacti are quite a hit in the plant trade and sadly people will pay big money for rare specimens. The endangered status of the Pima pineapple cactus makes it a prized target for greedy collectors. 

The future of the Pima pineapple cactus is decidedly uncertain. Thankfully its placement on the endangered species list has afforded it a bit more attention from a conservation standpoint. Still, we know very little about this plant and more data are going to be needed if we are to develop sound conservation measures. This, my friends, is why land conservation is so important. Plants like the Pima pineapple cactus need places to grow. If we do not work harder on setting aside wild spaces, we will lose so much more than this species. 

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3]

California Bumblebee Decline Linked to Feral Honeybees

Photo by Alvesgaspar licensed under CC BY-SA 3.0

Worldwide, pollinators are having a rough go of it. Humans have altered the landscape to such a degree that many species simply can't keep up. The proverbial poster child for pollinator issues is the honeybee (Apis mellifera). As a result, countless native pollinators get the short shrift when it comes to media attention. This isn't good because outside of intense industrial agriculture, native pollinators make up the bulk of pollination services. Similarly, honeybee fandom often overshadows any potential negative effects these introduced insects might be having on native pollinators.

Long term scientific investigations are starting to paint a more nuanced picture of the impact introduced honeybees are having on native ecosystems. For instance, research based out of California is finding that honeybees are playing a big role in the decline of native bumblebee populations. What's more, these negative impacts are only made worse in the light of climate change.

Licensed under public domain

For over 15 years, ecologist Dr. Diane Thompson has been studying bumblebee populations in central California. At no point during those early years did any of the bumblebee species she focuses on show signs of decline. In fact, they were quite common. Then, around the year 2000, feral honeybees started to establish themselves in the area. Honeybee colonies were becoming more and more numerous each and every year and that is when she started noticing changes in bumblebee behavior and numbers.

You see, honeybees are extremely successful foragers. They are generalists, which means they can visit a wide variety of flower types. As a result, they are extremely good at competing for floral resources compared to native bumblebees. Her results show that increases in the number of honeybee colonies caused not only a reduction in foraging among the native bumblebees, they also caused a reduction in bumblebee colony success. The native bumblebees simply weren't raising as many young as they were before honeybees entered the system.

Decreased rainfall cause a decline in flower densities of Scrophularia californica, a key resource for native bumblebees in this system. Photo by USFWS - Pacific Region licensed under CC BY-NC 2.0

Climate change is only making things worse. As drought years become not only more severe but also more intense, the amount of flowers available during the growing season also declines. With fewer flowers on the landscape, bumblebees and honeybees are forced into closer proximity for foraging and the clear winner in most foraging disputes are the tenacious honeybees. As such, bumblebees are chased off the already diminishing floral displays. By 2014, Dr. Thompson had quantified a significant decline in native bumblebee populations as a result.

It would be all too convenient to say that this research represents an isolated case. It does not. More and more research is finding that honeybees frequently out-compete native pollinators for resources such as food and nesting sites. Such effects are especially pronounced in rapidly changing ecosystems. Although honeybees are here to stay, it is important that we realize the impacts that these feral insects are having on our native ecosystems and begin to better appreciate and facilitate the services provided by our native pollinators. 

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3] [4]

Are Algae Plants?

I was nibbling on some nori the other day when a thought suddenly hit me. I don't know squat about algae. I know it comes in many shapes, sizes, and colors. I know it is that stuff that we used to throw at each other on the beach. I know that it photosynthesizes. That's about it. What are algae? Are they even plants?

The shortest answer I can give you is "it depends." The term algae is a bit nebulous in and of itself. In Latin, the word "alga" simply means "seaweed." Algae are paraphyletic, meaning they do not share a recent common ancestor with one another. In fact, without specification, algae may refer to entirely different kingdoms of life including Plantae (which is often divided in the broad sense, Archaeplastida and the narrow sense, Viridiplantae), Chromista, Protista, or Bacteria.

Caulerpa racemosa, a beautiful green algae. Photo by Nhobgood Nick Hobgood licensed under CC BY-SA 3.0

Taxonomy being what it is, these groupings may differ depending on who you ask. The point I am trying to make here is that algae are quite diverse from an evolutionary standpoint. Even calling them seaweed is a bit misleading as many different species of algae can be found in fresh water as well as growing on land.

Take for instance what is referred to as cyanobacteria. Known commonly as blue-green algae, colonies of these photosynthetic bacteria represent some of the earliest evidence of life in the fossil record. Remains of colonial blue-green algae have been found in rocks dating back more than 4 billion years. As a whole, these types of fossils represent nearly 7/8th of the history of life on this planet! However, they are considered bacteria, not plants.

Diatoms (Chromista) are another enormously important group. The single celled, photosynthetic organisms are encased in beautiful glass shells that make up entire layers of geologic strata. They comprise a majority of the phytoplankton in the world's oceans and are important indicators of climate. However, they belong to their own kingdom of life - Chromista or the brown algae.

To bring it back to what constitutes true plants, there is one group of algae that really started it all. It is widely believed that land plants share a close evolutionary history with a branch of green algae known as the stoneworts (order Charales). These aquatic, multicellular algae superficially resemble plants with their stalked appearance and radial leaflets.

A nice example of a stonewort (Chara braunii). Photo by Show_ryu licensed under CC BY-SA 3.0

It is likely that land plants evolved from a Chara-like ancestor that may have resembling modern day hornworts that lived in shallow freshwater inlets. Estimates of when this happen go back as far as 500 million years before present. Unfortunately, fossil evidence is sparse for this sort of thing and mostly comes in the form of fossilized spores and molecular clock calculations.

Porphyra umbilicalis  - One of the many species of red algae frequently referred to as nori. Photo by Gabriele Kothe-Heinrich licensed under CC BY-SA 3.0

Now, to bring it back to what started me down this road in the first place. Nori is made from algae in the genus Porphyra, which is a type of Rhodophyta or red algae. Together with Chlorophyta (the green algae), they make up some of the most familiar groups of algae. They have also been the source of a lot of taxonomic debate. Recent phylogenetic analyses place the red algae as a sister group to all other plants starting with green algae. However, some authors prefer to take a broader look at the tree and thus lump red algae in a member of the plant kingdom. So, depending on the particular paper I am reading, the nori I am currently digesting may or may not be considered a plant in the strictest sense of the word. That being said, the lines are a bit blurry and frankly I don't really care as long as it tastes good.

Photo Credits: [1] [2] [3] [4] [5]

Further Reading: [1] [2] [3] [4]

How a Giant Parasitic Orchid Makes a Living

Photo by mutolisp licensed under CC BY-NC-SA 2.0

Imagine a giant vine with no leaves and no chlorophyll scrambling over decaying wood and branches of a warm tropical forest. As remarkable as that may seem, that is exactly what Erythrorchis altissima is. With stems that can grow to upwards of 10 meters in length, this bizarre orchid from tropical Asia is the largest mycoheterotrophic plant known to science.

Mycoheterotrophs are plants that obtain all of their energy needs by parasitizing fungi. As you can probably imagine, this is an extremely indirect way for a plant to make a living. In most instances, this means the parasitic plants are stealing nutrients from the fungi that were obtained via a partnership with photosynthetic plants in the area. In other words, mycoheterotrophic plants are indirectly stealing from photosynthetic plants.

In the case of E. altissima, this begs the question of where does all of the carbon needed to build a surprising amount of plant come from? Is it parasitizing the mycorrhizal network associated with its photosynthetic neighbors or is it up to something else? These are exactly the sorts of questions a team from Saga University in Japan wanted to answer.

Photo by mutolisp licensed under CC BY-NC-SA 2.0

All orchids require fungal partners for germination and survival. That is one of the main reasons why orchids can be so finicky about where they will grow. Without the fungi, especially in the early years of growth, you simply don't have orchids. The first step in figuring out how this massive parasitic orchid makes its living was to identify what types of fungi it partners with. To do this, the team took root samples and isolated the fungi living within.

By looking at their DNA, the team was able to identify 37 unique fungal taxa associated with this species. Most surprising was that a majority of those fungi were not considered mycorrhizal (though at least one mycorrhizal species was identified). Instead, the vast majority of the fungi associated with with this orchid are involved in wood decay.

Stems climbing on fallen dead wood (a) or on standing living trees (b). A thick and densely branched root clump (c) and thin and elongate roots (d) [Source]

To ensure that these wood decay fungi weren't simply partnering with adult plants, the team decided to test whether or not the wood decay fungi were able to induce germination of E. altissima seeds. In vitro germination trials revealed that not only do these fungi induce seed germination in this orchid, they also fuel the early growth stages of the plant. Further tests also revealed that all of the carbon and nitrogen needs of E. altissima are met by these wood decay fungi.

These results are amazing. It shows that the largest mycoheterotrophic plant we know of lives entirely off of a generalized group of fungi responsible for the breakdown of wood. By parasitizing these fungi, the orchid has gained access to one of the largest pools of carbon (and other nutrients) without having to give anything back in return. It is no wonder then that this orchid is able to reach such epic proportions without having to do any photosynthesizing of its own. What an incredible world we live in!

Photo by mutolisp licensed under CC BY-NC-SA 2.0

Photo Credits: [1] [2]

Further Reading: [1]

How Air Plants Drink

 Tillandsia tectorum. Photo by Edu licensed under CC BY-NC-ND 2.0

Air plants (genus Tillandsia) are remarkable organisms. All it takes is seeing one in person to understand why they have achieved rock star status in the horticulture trade. Unlike what we think of as a "traditional" plant lifestyle, most species of air plants live a life free of soil. Instead, they attach themselves to the limbs and trunks of trees as well as a plethora of other surfaces. 

Living this way imposes some serious challenges. The biggest of these is the acquisition of water. Although air plants are fully capable of developing roots, these organs don't live very long and they are largely incapable of absorbing anything from the surrounding environment. The sole purpose of air plant roots is to anchor them to whatever they are growing on. How then do these plants function? How do they obtain water and nutrients? The answer to this lies in tiny structures called trichomes. 

Trichomes are what gives most air plants their silvery sheen. To fully appreciate how these marvelous structures work, one needs some serious magnification. A close inspection would reveal hollow, nail-shaped structures attached to the plant by a stem. Instead of absorbing water directly through the leaf tissues, these trichomes mediate the process and, in doing so, prevent the plant from losing more water than it gains. 

The trichomes themselves start off as living tissue. During development, however, they undergo programmed cell death, leaving them hollow. When any amount of moisture comes into contact with these trichomes, they immediately absorb that water, swelling up in the process. As they swell, they are stretched out flat along the surface of the leaf. This creates a tiny film of water between the trichomes and the rest of the leaf, which only facilitates the absorption of more water. 

Trichomes up close.  Photo by Mark Smith1989 licensed under CC BY-SA 4.0

Because the trichomes form a sort of conduit to the inside of the leaf, water and any nutrients dissolved within are free to move into the plant until the reach the spongy mesophyll cells inside. In this way, air plants get all of their water needs from precipitation and fog. Not all air plants have the same amount of trichomes either. In fact, trichome density can tell you a lot about the kind of environment a particular air plant calls home. 

Photo by Bernard DUPONT licensed under CC BY-SA 2.0

The fuzzier the plant looks, the drier the habitat it can tolerate. Take, for instance, one of the fuzziest air plants - Tillandsia tectorum. This species hails from extremely arid environments in the high elevation regions of Ecuador and Peru. This species mainly relies on passing clouds and fog for its moisture needs and thus requires lots of surface area to collect said water. Now contrast that with a species like Tillandsia bulbosa, which appears to have almost no trichome cover. This smoother looking species is native to humid low-land habitats where high humidity and frequent rain provide plenty of opportunities for a drink. 

Photo by Bocabroms licensed under CC BY-SA 3.0

Absorbing water in this way would appear to have opened up a plethora of habitats for the genus Tillandsia. Air plants are tenacious plants and worthy of our admiration. One could learn a lot from their water savvy ways. 

Photo Credits: [1] [2] [3] [4]

Further Reading: [1] [2] [3]

Rein In Those Seeds

Photo by Stan Shebs licensed under CC BY-SA 3.0

Plants living on islands face a bit of a conundrum. In order to get to said islands, the ancestors of those plants had to exhibit extreme seed or spore dispersal strategies. However, if plants are to persist after arriving to an island, long-distance dispersal becomes rather risky. In the case of oceanic islands, seeds or spores that travel too far end up in the water. As such, we often observe an evolutionary reduction in dispersal ability for island residents. 

Islands, however, are not always surrounded by water. You can have "islands" on land as well. The easiest example for most to picture would be the alpine zone of a mountain. Species adapted to these high-elevation habitats find it hard to compete with species native to low-elevation habitats and are therefore stuck on these "islands in the sky." Less obvious are islands created by a specific soil type. 

Take, for instance, gypseous soils. Such soils are the result of large amounts of gypsum deposits at or near the soil surface. Gypseous soils are found in large quantities throughout parts of western North America, North and South Africa, western Asia, Australia, and eastern Spain. They are largely the result of a massive climatic shift that occurred during the Eocene, some 50 million years ago. 

Licensed under public domain

Massive mountain building events during that time were causing large reductions in atmospheric CO2 concentrations. The removal of this greenhouse gas via chemical weathering caused a gradual decline in average temperatures around the world. Earth was also becoming a much drier place and throughout the areas mentioned above, hyper-saline lakes began to dry up. As they did, copious amount of minerals, including gypsum, were left behind. 

These mineral-rich soils differ from the surrounding soils in that they contain a lot of salts. Salt makes life incredibly difficult for most terrestrial plants. Life finds a way, however, and a handful of plant species inevitably adapted to these mineral-rich soils, becoming specialists in the process. They are so specialized on these types of soils that they simply cannot compete with other plant species when growing in more "normal" soils. 

Essentially, these gypseous soils function like soil or edaphic islands. Plants specialized in growing there really don't have the option to disperse far and wide. They have to rein it in or risk extirpation. For a group of plants growing in gypseous soils in western North America, this equates to changes in seed morphology. 

Mentzelia is a genus of flowering plants in the family Loasaceae. There are somewhere around 60 to 70 different species, ranging from annuals to perennials, and forbs to shrubs (they are often referred to as blazing stars but since that would lead to too much confusion with Liatris, I will continue to refer to them as Mentzelia).

For most species in this genus, seed dispersal is accomplished by wind. Plants growing on "normal" soils produce seeds with a distinct wing surrounding the seed. A decent breeze will dislodge them from their capsule, causing them blow around. With any luck some of those seeds will land in a suitable spot for germination, far from their parents. Such is not the case for all Mentzelia though. When researchers took a closer look at species that have specialized on gypseous soils, they found something intriguing. 

Mentzelia phylogeny showing reduction in seed wings. [source]

The wings surrounding the seeds of gypseous Mentzelia were either extremely reduced in size or had disappeared altogether. Just as it makes no sense for a plant living on an oceanic island to disperse its seeds far out into the ocean, it too makes no sense for gypseous Mentzelia to disperse their seeds into soils in which they cannot compete. It is thought that limited dispersal may help reinforce the types of habitat specialization that we see in species like these Mentzelia. The next question that must be answered is whether or not such specialization and limited dispersal comes at the cost of genetic diversity. More work will be needed to understand such dynamics. 

Photo Credits: [1] [2] [3]

Further Reading: [1] [2]

Mt. Cuba Center Puts Nativars to the Test

By this point, most gardeners will have undoubtedly heard about the importance of using native plants in our landscapes. Though the idea is not new, Doug Tallamy’s landmark publication “Bringing Nature Home” put native plants on the radar for more gardeners than ever. There is no debate that utilizing native plants in our landscapes offers us a chance to bring back some of the biodiversity that was lost when our homes and work places were built. And, at the end of the day, who doesn’t love the sight of a swallowtail butterfly flitting from flower to flower or a pair of warblers nesting in their Viburnum? The rise of native plants in horticulture and landscaping is truly something worth celebrating.

At the same time, however, capitalism is capitalism, and many nurseries are starting to jump on the bandwagon in alarming ways. The rise of native cultivars or “nativars” is troubling to many. Nativars are unique forms, colors, and shapes of our beloved native plants which have been selected and propagated by nurseries and plant breeders. This has led many to denounce the practice of planting nativars as a slap in the face to the concept of native gardening.

Nativars are frequently seen as unnatural mutant versions of their wild counterparts whose use overlooks the whole point of natives in the first place. Take, for instance, the popularity of double flowered nativars. These plants have been selected for an over-production of sepals and petals that can be so dense that they preclude visitation by pollinators. Another example that will be familiar to most are the bright blue hydrangeas that have become to popular. These shrubs have been selected for producing bright, showy flowers that, depending on your soil chemistry, exhibit a stunning blue coloration. The downside here is that all of those flowers are sterile and produce no nectar or pollen for visiting insects.

It would seem that nativars are a slippery slope to yet another sterile landscape incapable of supporting biodiversity. However, anecdotes don’t equal data and that is where places like Mt. Cuba Center come in. Located in northern Delaware, Mt. Cuba is doing something quite amazing for the sake of environmentally friendly landscaping – they are putting plants to the test.

Mt. Cuba has been running trial garden research and experiments on native plants and their nativars for over a decade. The goal of this research is to generate and analyze data in order to help the public make better, more sustainable choices for their yards. Mt. Cuba aims to better understand and quantify the horticultural and ecological value of native plants and related nativars in order to better understand the various ecosystem services these plants provide. In collaboration with academic institutions in the region, popular nativars are established and grown under similar conditions to those experienced in the yards of your average gardener. They are monitored for years to assess their overall health, performance, and ability to support wildlife. Thanks to the help of countless volunteers, these trial gardens paint a holistic picture of each plant and related nativars that is sorely lacking from the gardening lexicon.

This is very exciting research to say the least. The data coming out of the Mt. Cuba trial gardens may both surprise and excite gardeners throughout the mid-Atlantic region of North America. For instance, their latest report looked at some of the most common Phlox varieties on the market. At the top of this list is Garden Phlox (Phlox paniculata). This lovely species is native throughout much of the eastern United States and has become quite a rockstar in the nursery trade. Over 580 cultivars and hybrids have been named to date and no doubt many more will be introduced in the future. Amazingly, many of these Phlox nativars are being developed in the Netherlands. As such, Phlox arriving in regions of the US with vastly different climates often fall victim to novel diseases they never encountered in Europe. What’s more, people often plant these nativars in hopes of attracting butterflies to their garden. Despite their popularity for attracting various lepidopterans, no one has ever tested whether or not the nativars perform as well as their native progenitor.

Phlox paniculata 'Delta Snow'

Starting in 2015, Mt. Cuba began trials on 66 selections and hybrids of Garden Phlox along with 28 other sun-loving types of Phlox. The plants were observed on a regular basis to see which of the nativars experienced the least amount of disease and attracted the most insects. The clear winner of these trails is a nativar known as Phlox paniculata ‘Jeana’. This particular selection was discovered growing along the Harpeth River in Tennessee and is known for having the smallest flowers of any of the Garden Phlox varieties. It also has the reputation for being rather resistant to powdery mildew. Alongside other selections such as Delta Sno’ and David, Jeana really held up to this reputation.

As far as butterflies are concerned, Jeana blew its competition out of the water. Throughout the observation period, Jeana plants received over 530 visits from butterflies whereas the second place selection, Lavelle, received 117. A graduate student at the University of Delaware is studying why exactly the various nativars of Phlox paniculata differ so much in insect visitation. Though they haven’t zeroed in on a single cause at this point, they suggest that the popularity of Jeana might actually have something to do with its small flower size. Perhaps the density of smaller flowers allows butterflies to access more nectar for less effort.

Phlox paniculata ‘Jeana’

Monarda is another genus of North American native plants that has seen an explosion in nativars and hybrids over the last few decades. The popularity of these mints is no surprise to anyone who has spent time around them. Their inflorescence seems to be doing their best impression of a fireworks display, an attribute that isn’t lost on pollinators. These plants are popular with a wide variety of wildlife from solitary bees to voracious hummingbirds. Even after flowering, their seeds provide food for seed-eating birds and many other animals.

As with Garden Phlox, a majority of the commercial selection and hybridization of Monarda occurs in Europe. As a result, resistance to North American plant diseases is not top priority. Many of us have experienced this first hand as our beloved bee balm patch succumbs to aggressive strains of powdery mildew. Though there are many species of Monarda native to North America, most of the plants we encounter are nativars and hybrids of two species – Monarda didyma and Monarda fistulosa.

Monarda fistulosa 'Claire Grace'

Again, Mt. Cuba’s trial gardens put these plants to the test. A total of 40 different Monarda selections were grown, observed, and ranked based on their overall growth and vigor, pollinator attractiveness, and disease resistance. The clear winner of these trials was a naturally-occurring form of M. fistulosa affectionately named ‘Claire Grace.’ Its floral display lasts a total of 3 weeks without waning and managed to attract over 130 visits by butterflies and moths. Though plenty of other insects such as short-tongued bees visited the flowers during the trial period, they are too small to properly access the nectar inside the flower tubes and are therefore not considered effective pollinators.

Another clear winner in terms of pollinators was possibly one of the most stunning Monarda selections in existence – Monarda didyma ‘Jacob Cline’. This tall, red-flowering nativar was a major hit with hummingbirds. During the observation period, Jacob Cline received over 270 visits from these brightly colored birds. Researchers are still trying to figure out why exactly this particular selection was such a hit but they speculate that the large flower size presents ample feeding opportunities for tenacious hummingbirds.

Monarda didyma 'Jacob Cline'

Claire Grace and Jacob Cline also outperformed most of the other selections in terms of disease resistance. Even in the crowded conditions experienced by plants in the trail garden, both selections faired quite well against the dreaded powdery mildew. Though they aren’t completely resistant to it, these and others did not succumb like some selections tend to do. Interestingly enough, most of the other pure species tested in the trial faired quite well against powdery mildew as well. It would appear that Mother Nature better equips these plants than European breeders.

These reports are but two of the many trials that Mt. Cuba has undertaken and there are many, many more on the way. Thanks to the hard work of staff and volunteers, Mt. Cuba is finally putting numbers behind some of our most commonly held assumptions about gardening with native plants and their cultivars. It is impressive to see a place so dedicated to making our landscapes more sustainable and environmentally friendly.

If you would like to find out more about Mt. Cuba’s trial garden as well as download your own copies of the trial garden reports, please make sure to check out https://mtcubacenter.org/research/trial-garden/

Hydatellaceae: The Other Basal Angiosperms

Photo by Kevin Thiele licensed under CC BY 2.0

Though rather obscure to most of the world, the genus Trithuria has enjoyed somewhat of a celebrity status in recent years. A paper published in 2007 lifted this tiny group of minuscule aquatic plants out of their spot in Poales and granted them a place among the basal angiosperm lineage Nymphaeales. This was a huge move for such little plants. 

The genus Trithuria contains 12 species, the majority of which reside in Australia, however, two species, T. inconspicua and T. konkanensis, are native to New Zealand and India. They are all aquatic herbs and their diminutive size and inconspicuous appearance make them easy to miss. For quite some time these odd plants were considered to be a group of highly reduced monocots. Their original placement was in the family Centrolepidaceae. All of that changed in 2007.

Close inspection of Trithuria DNA told a much different story. These were not highly reduced monocots after all. Instead, multiple analyses revealed that Trithuria were actually members of the basal angiosperm lineage Nymphaeales. Together with the water lilies (Nymphaeaceae) and the fanworts (Cabombaceae), these plants are living representatives of some of the early days in flowering plant evolution. 

Of course, DNA analysis cannot stand on its own. The results of the new phylogeny had to be corroborated with anatomical evidence. Indeed, closer inspection of the anatomy of Trithuria revealed that these plants are truly distinct from members of Poales based on a series of features including furrowed pollen grains, inverted ovules, and abundant starchy seed storage tissues. Taken together, all of these lines of evidence warranted the construction of a new family - Hydatellaceae.

The 12 species of Trithuria are rather similar in their habits. Many live a largely submerged aquatic lifestyle in shallow estuarine habitats. As you may have guessed, individual plants look like tiny grass-like rosettes. Their small flower size has lent to some of their taxonomic confusion over the years. What was once thought of as individual flowers were revealed to be clusters or heads of highly reduced individual flowers. 

Reproduction for these plants seems like a tricky affair. Some have speculated that water plays a role but close inspections of at least one species revealed that very little pollen transfer takes place in this way. Wind is probably the most common way in which pollen from one plant finds its way to another, however, the reduced size of these flowers and their annual nature means there isn't much time and pollen to go around. It is likely that most of the 12 species of Trithuria are self-pollinated. This is probably quite useful considering the unpredictable nature of their aquatic habitats. It doesn't take much for these tiny aquatic herbs to establish new populations. In total, Trithuria stands as living proof that big things often come in small packages. 

Photo Credits: [1]

Further Reading: [1] [2] [3]

Saving Bornean Peatlands is a Must For Conservation

Photo by Dukeabruzzi licensed under CC BY-SA 4.0

The leading cause of extinction on this planet is loss of habitat. As an ecologist, it pains me to see how frequently this gets ignored. Plants, animals, fungi - literally every organism on this planet needs a place to live. Without habitat, we are forced to pack our flora and fauna into tiny collections in zoos and botanical gardens, completely disembodied from the environment that shaped them into what we know and love today. That’s not to say that zoos and botanical gardens don’t play critically important roles in conservation, however, if we are going to stave off total ecological meltdown, we must also be setting aside swaths of wild lands.

There is no way around it. We cannot have our cake and eat it too. Land conservation must be a priority both at the local and the global scale. Wild spaces support life. They buffer life from storms and minimize the impacts of deadly diseases. Healthy habitats filter the water we drink and, for many people around the globe, provide much of the food we eat. Every one of us can think back to our childhood and remember a favorite stretch of stream, meadow, or forest that has since been gobbled up by a housing development. For me it was a forested stream where I learned to love the natural world. I would spend hours playing in the creek, climbing trees, and capturing bugs to show my parents. Since that time, someone leveled the forest, built a house, and planted a lawn. With that patch of forest went all of the insects, birds, and wildflowers it once supported.

Scenarios like this play out all too often and sadly on a much larger scale than a backyard. Globally, forests have taken the brunt of human development. It is hard to get a sense of the scope of deforestation on a global scale, but the undisputed leaders in deforestation are Brazil and Indonesia. Though the Amazon gets a lot of press, few may truly grasp the gravity of the situation playing out in Southeast Asia.

Deforestation is a clear and present threat throughout tropical Asia. This region is growing both in its economy and population by about 6% every year and this growth has come at great cost to the environment. Indonesia (alongside Brazil) accounts for 55% of the world’s deforestation rates. This is a gut-wrenching statistic because Indonesia alone is home to the most extensive area of intact rainforest in all of Asia. So far, nearly a quarter of Indonesia’s forests have been cleared. It was estimated that by 2010, 2.3 million hectares of peatland forests had been felled and this number shows little signs of slowing. Experts believe that if these rates continue, this area could lose the remainder of its forests by 2056.

Consider the fact that Southeast Asia contains 6 of the world’s 25 biodiversity hotspots and you can begin to imagine the devastating blow that the levelling of these forests can have. Much of this deforestation is done in the name of agriculture, and of that, palm oil and rubber take the cake. Southeast Asia is responsible for producing 86% of the world’s palm oil and 87% of the world’s natural rubber. What’s more, the companies responsible for these plantations are ranked among some of the least sustainable in the world.

Borneo is home to a bewildering array of life. Researchers working there are constantly finding and describing new species, many of which are found nowhere else in the world. Of the roughly 15,000 plant species known from Borneo, botanists estimate that nearly 5,000 (~34%) of them are endemic. This includes some of the more charismatic plant species such as the beloved carnivorous pitcher plants in the genus Nepenthes. Of these, 50 species have been found growing in Borneo, many of which are only known from single mountain tops.

It has been said that nowhere else in the world has the diversity of orchid species found in Borneo. To date, roughly 3,000 species have been described but many, many more await discovery. For example, since 2007, 51 new species of orchid have been found. Borneo is also home to the largest flower in the world, Rafflesia arnoldii. It, along with its relatives, are parasites, living their entire lives inside of tropical vines. These amazing plants only ever emerge when it is time to flower and flower they do! Their superficial resemblance to a rotting carcass goes much deeper than looks alone. These flowers emit a fetid odor that is proportional to their size, earning them the name “carrion flowers.”

Rafflesia arnoldii in all of its glory. Photo by SofianRafflesia licensed under CC BY-SA 4.0

Photo by Orchi licensed under CC BY-SA 3.0

If deforestation wasn’t enough of a threat to these botanical treasures, poachers are having considerable impacts on Bornean botany. The illegal wildlife trade throughout southeast Asia gets a lot of media attention and rightfully so. At the same time, however, the illegal trade of ornamental and medicinal plants has gone largely unnoticed. Much of this is fueled by demands in China and Vietnam for plants considered medicinally valuable. At this point in time, we simply don’t know the extent to which poaching is harming plant populations. One survey found 347 different orchid species were being traded illegally across borders, many of which were considered threatened or endangered. Ever-shrinking forested areas only exacerbate the issue of plant poaching. It is the law of diminishing returns time and time again.

Photo by Orchi licensed under CC BY-SA 3.0

But to lump all Bornean forests under the general label of “rainforest” is a bit misleading. Borneo has multitude of forest types and one of the most globally important of these are the peatland forests. Peatlands are vital areas of carbon storage for this planet because they are the result of a lack of decay. Whereas leaves and twigs quickly breakdown in most rainforest situations, plant debris never quite makes it that far in a peatland. Plant materials that fall into a peatland stick around and build up over hundreds and thousands of years. As such, an extremely thick layer of peat is formed. In some areas, this layer can be as much as 20 meters deep! All the carbon tied up in the undecayed plant matter is carbon that isn’t finding its way back into our atmosphere.

Sadly, tropical peatlands like those found in Borneo are facing a multitude of threats. In Indonesia alone, draining, burning, and farming (especially for palm oil) have led to the destruction of 1 million hectares (20%) of peatland habitat in only a single decade. The fires themselves are especially worrisome. For instance, it was estimated that fires set between 1997-1998 and 2002-2003 in order to clear the land for palm oil plantations released 200 million to 1 billion tonnes of carbon into our atmosphere. Considering that 60% of the world’s tropical peatlands are found in the Indo-Malayan region, these numbers are troubling.

The peatlands of Borneo are totally unlike peatlands elsewhere in the world. Instead of mosses, gramminoids, and shrubs, these tropical peatlands are covered in forests. Massive dipterocarp trees dominate the landscape, growing on a spongey mat of peat. What’s more, no water flows into these habitats. They are fed entirely by rain. The spongey nature of the peat mat holds onto water well into the dry season, providing clean, filtered water where it otherwise wouldn’t be available.

Photo by JeremiahsCPs licensed under CC BY-SA 3.0

This lack of decay coupled with their extremely acidic nature and near complete saturation makes peat lands difficult places for survival. Still, life has found a way, and Borneo’s peatlands are home to a staggering diversity of plant life. They are so diverse, in fact, that when I asked Dr. Craig Costion, a plant conservation officer for the Rainforest Trust, for something approaching a plant list for an area of peatland known as Rungan River region, he replied:

“Certainly not nor would there ever be one in the conceivable future given the sheer size of the property and the level of diversity in Borneo. There can be as many as a 100 species per acre of trees in Borneo... Certainly a high percentage of the species would only be able to be assigned to a genus then sit in an herbarium for decades until someone describes them.”

And that is quite remarkable when you think about it. When you consider that the Rungan River property is approximately 385,000 acres, the number of plant species to consider quickly becomes overwhelming. To put that in perspective, there are only about 500 tree species native to the whole of Europe! And that’s just considering the trees. Borneo’s peatlands are home to myriad plant species from liverworts, mosses, and ferns, to countless flowering plants like orchids and others. We simply do not know what kind of diversity places like Borneo hold. One could easily spend a week in a place like the Rungan River and walk away with dozens of plant species completely new to science. Losing a tract of forest in such a biodiverse region is a huge blow to global biodiversity.

Nepenthes ampullaria relies on decaying plant material within its pitcher for its nutrient needs. Photo by en:User:NepGrower licensed under Public Domain

Also, consider that all this plant diversity is supporting even more animal diversity. For instance, the high diversity of fruit trees in this region support a population of over 2,000 Bornean orangutans. That is nearly 4% of the entire global population of these great apes. They aren’t alone either, the forested peatlands of Borneo are home to species such as the critically endangered Bornean white-bearded gibbon, the proboscis monkey, the rare flat-headed cat, and the oddly named otter civet. All these animals and more rely on the habitat provided by these forests. Without forests, these animals are no more.

The flat-headed cat, an endemic of Borneo. Photo by Jim Sanderson licensed under CC BY-SA 3.0

At this point, many of you may be feeling quite depressed. I know how easy it is to feel like there is nothing you can do to help. Well, what if I told you that there is something you can do right now to save a 385,000 acre chunk of peatland rainforest? That’s right, by heading over to the Rainforest Trust’s website (https://www.rainforesttrust.org/project/saving-stronghold-critically-endangered-bornean-orangutan/) you can donate to their campaign to buy up and protect the Rungan River forest tract.

Click on the logo to learn more!

By donating to the Rainforest Trust, you are doing your part in protecting biodiversity in one of the most biodiverse regions in the world. What’s more, you can rest assured that your money is being used effectively. The Rainforest Trust consistently ranks as one of the top environmental protection charities in the world. Over their nearly three decades of operation, the Rainforest Trust has protected more than 15.7 million acres of land in over 20 countries. Like I said in the beginning, habitat loss is the leading cause of extinction on this planet. Without habitat, we have nothing. Plants are that habitat and by supporting organizations such as the Rainforest Trust, you are doing your part to fight the biggest threats our planet faces. 

Further Reading: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Photo Credits: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

Ferns Afloat

Photo by Le.Loup.Gris licensed under CC BY-SA 3.0

My introduction to the genus Salvinia was as an oddball aquarium plant floating in a display tank at the local pet store. I knew nothing about plants at the time but I found it to be rather charming nonetheless. Every time the green raft of leaves floated under the filter outlet, water droplets would bead off them like water off of a ducks back. Even more attractive were the upside down forest of "roots" which were actively sheltering a bunch of baby guppies. 

I grew some Salvinia for a few years before my interest in maintaining aquariums faded. I had forgotten about them for quite some time. Much later as I was diving into the wild world of botany, I started revisiting some of the plants that I had grown in various aquariums to learn more about them. It wasn't long before the memory of Salvinia returned. A quick search revealed something astonishing. Salvinia are not flowering plants. They are ferns! 

The genus Salvinia is wide spread. They can be found growing naturally throughout North, Central, and South America, the West Indies, Europe, Africa, and Madagascar. Sadly, because of their popularity as aquarium and pond plants, a few species have become extremely aggressive invaders in many water ways. More on that in a bit. 

Salvinia comprises roughly 12 different species. Of these, at least 4 are suspected to be naturally occurring hybrids. As you have probably already gathered, these ferns live out their entire lives as floating aquatic plants. Their most obvious feature are the pairs of fuzzy green leaves borne on tiny branching stems. These leaves are covered in trichomes that repel water, thus keeping them dry despite their aquatic habit. 

These are not roots! Photo by Carassiuslike licensed under CC BY-SA 4.0

Less obvious are the other types of leaves these ferns produce. What looks like roots dangling below the water's surface are actually highly specialized, finely dissected leaves! I was super shocked to learn this and to be honest, it makes me appreciate these odd little ferns even more. It is on those underwater leaves that the spores are produced. Specialized structures called sporocarps form like tiny nodules on the tips of the leaf hairs.

Sporocarps come in two sizes, each producing its own kind of spore. Large sporocarps produce megaspores while the smaller sporocarps produce microspores. This reproductive strategy is called heterospory. Microspores germinate into gametophytes containing male sex organs or "antheridia," whereas the megaspores develop into gametophytes containing female sex organs or "archegonia." 

As I mentioned above, some species of Salvinia have become aggressive invaders, especially in tropical and sub-tropical water ways. Original introductions were likely via plants released from aquariums and ponds but their small spores and vegetative growth habit means new introductions occur all too easily. Left unchecked, invasive Salvinia can form impenetrable mats that completely cover entire bodies of water and can be upwards of 2 feet thick!

Sporocarps galore! Photo by Kenraiz licensed under CC BY-SA 4.0

Lots of work has been done to find a cost effective way to control invasive Salvinia populations. A tiny weevil known scientifically as Cyrtobagous singularis has been used with great success in places like Australia. Still, the best way to fight invasive species is to prevent them from spreading into new areas. Check your boots, check your boats, and never ever dump your aquarium or pond plants into local water ways. Provided you pay attention, Salvinia are rather fascinating plants that really break the mold as far as most ferns are concerned. 

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3]