My Little Pernicious Buttercup
The spring ephemeral wildflower that has crept its way to dominance
It doesn’t look like much, does it?
It’s just a cute little buttercup: the sort of thing you might hold under your chin to measure your fondness for butter. But don’t be fooled. These buttercups, specifically known as lesser celandine (Ficaria verna) are brutes. They have taken over the forest floors in much of the Philadelphia area, and there is apparently no stopping them.
Most forest visitors justifiably appreciate the lush carpet of green studded with yellow flowers on their spring hikes. An understory of lesser celandine is beautiful, even if its impact is ugly. We’ve got plenty of native wildflowers with a similar “spring ephemeral” life history: sprout and blossom early in the spring before the trees leaf out and block all the sun, and then die back and wait until next spring. The lesser celandine leaves them nowhere to grow.
These buttercups come from Europe, and like many of our most pernicious weeds, we brought them over on purpose as garden plants. The same features that made them great in a garden - resistance to diseases and insects, unpalatability to larger herbivores - give them an advantage over our native plants that occupy a similar niche. They also are easy to spread. Just under the surface of the soil they form little tubers. Each little tuber can resprout and, over the years, spread outward into a patch that continually sheds more tubers. These are easily spread in the tread of shoe soles or tires. When it rains, the tubers easily wash downhill to colonize new terrain.
Almost all the wooded parks in Philadelphia are downhill. In Phoenix the rugged hills that project up from the flat city have been preserved as parks, but in Philadelphia, and much of the Mid-Atlantic, we have built our parks on the low land along waterways. You can imagine them under assault for more than a hundred years by the gardens above, releasing little buttercup bombs that grew as little patches until, these days, they carpet the forest.
It’s not just the buttercups that hold back our native spring ephemerals. Our forest floors are a mess. Invasive earthworms (we have no locally native earthworms in Philadelphia) devour leaf litter, stripping the ground of the mat of springy decaying plant matter that used to buffer it. An overabundance of deer do the same to plants they evolved eating, giving a boost to plants they don’t like, such as lesser celandine. We suppress fire, which was a lot more common in our pre-colonization forests than we appreciate.*
I don’t know how we would get back to a landscape of native spring wildflowers here, but I think it’s worth keeping that as our goal. All the problems I listed are intractable. We have had some success in reducing deer populations, but not enough. I’d love to light the Cobbs Creek or Wissahickon understory on fire, but I doubt the people living next to the park would appreciate that. No one has any good ideas for getting rid of exotic earthworms at scale. And lesser celandine (itself a spring ephemeral) is nearly impossible to eradicate. There’s no way to get rid of all those itty bitty tubers without completely ripping up the soil, and spraying herbicides over thousands of acres will go over like a lead balloon.
But not knowing how to get there from here isn’t a reason to give up the goal. The opposite perspective - that in a novel urban ecosystem we should embrace the species that succeed, whether or not they’re native - seems increasingly popular, but I’m not a fan.
It was on a hike a few years ago in the Blue Ridge Mountains of Virginia that I fully appreciated what we’ve lost. It was in April, and I was stopping on a road trip for a break to stretch my legs and look for salamanders. The canopy hadn’t leafed out yet, and all around me were flowers like trilliums and star chickweed. In Philadelphia our native spring ephemerals grow either in relict patches of relatively-intact forest, as at the Schuylkill Center for Environmental Education, or are the subjects of limited restoration campaigns. Seeing them growing widespread in a forest all on their own was a revelatory experience. And it’s an experience we all deserve, even if it might take us a while to recreate it.
*Most of the discussion of fire as an ecological management tool comes from out West, but our Northeastern forests evolved with fire as well. Indigenous peoples lit fires intentionally to provide forage for game, to drive deer during hunting trips (in other words lighting fires to scare deer in the direction of hunters waiting in ambush), and for a gillion other smaller-scale uses that must have resulted in occasional burns escaping into the wider landscape. For example they used fire to clear fields for planting crops. When they wanted to take down a large tree, they did it by lighting fires around its base and burning the outer wood, layer by layer (laborious, but a lot easier than cutting down an oak tree with stone hand axes). The result was a mix of species on the forest floor and the canopy that were adapted to occasional burns.