There are many species of small, nondescript spurge out there. All too often they go completely unnoticed, even by plant lovers like myself. As I have come to learn time and time again, every species has an interesting story to tell. That is why I started In Defense of Plants in the first place. The story I want to tell you today came to me from a chance encounter I had while exploring a beach on Lake Erie. I was musing over some tumbleweed I had found when I noticed some small spurge barely poking out of the sand around me. I took some pictures and moved on. Had I realized what I would come to learn from this spurge, I probably would have spent more time admiring it.
Our story begins roughly 18,000 years ago during the height of the last glacial period. Much of northern North America was buried under a massive glacial ice sheet. This was unlike anything we can witness on the continent today. In some spots the ice was well over a mile thick. The weight of that much ice on the land caused the bedrock underneath to compress, not unlike a mattress compresses under the weight of a human body. This compression pushed much of northeastern North America lower than sea level. Unlike a mattress, however, rock can take a very long time to rebound after the weight has been lifted. Around 13,000 years ago when the glaciers began to retreat, the land was still compressed below sea level.
Map via Orbitale licensed under CC BY-SA 3.0
With the ice gone, the ocean quickly rushed in to fill what is now the St. Lawrence and Ottawa River valleys as well as Lake Champlain. A salty inland lake coined the Champlain Sea was the result of this influx of ocean water. For some time, the Champlain Sea provided seemingly out of place maritime habitat until isostatic rebound caused the land to rise enough to drain it some 10,000 years ago. During this period, the Champlain Sea was home to animals typically seen in the northern Atlantic today including whales, whose fossils have been found in parts of Montreal and Ottawa. Coastal plant communities formed along the shores of the Champlain Sea, which brings me back to my little spurge friend.
Inland beach pea (Lathyrus japonicus). Photo by Alastair Rae licensed under CC BY-SA 2.0
Sea rocket (Cakile edentula)
The species in question is Chamaesyce polygonifolia, the seaside spurge. By no means rare, this obscure little plant is more typically found along the coast of the Atlantic. Along with other species like the inland beach pea (Lathyrus japonicus) and sea rocket (Cakile edentula), these plants followed the shores of the Champlain Sea and remained here in sandy, disturbed habitats ever since. These species are echoes of a brief period of time when North America was going through a lot of changes. Again, had I known this at the time, I don't know if I would have left the beach so quickly that day. I love to be reminded of how small we really are, how fleeting our existence really is. I love meeting species that are players in a much bigger story and Chamaesyce polygonifolia and company are just that.