Invasives and Nuance

I’ve had a long and complicated relationship with Cup Plant (Silphium perfoliatum), and we finally broke up for good this year. The opening photo shows C. perfoliatum’s cousin, Compass Plant (Silphium laciniatum). It’s Invasive Species Awareness Week, so I thought maybe it’s a good time to open up about my experience of Cup Plant, so we can have a loving discourse about how complicated these issues can be and why. When speaking of our ecosystem and anything we voluntarily add to it, it is good to be attuned to nuance.

When I was first studying ecological gardening in 2005, the ecologist I apprenticed with refered to S. perfoliatum as a native plant, and one she was really fond of. The national websites I use to determine a species locality were mealymouthed at best, most seemed to indicate Cup Plant is found in NY but as per usual gave no regional specific information.

As time went on I came into new information about this species classification. I learned that it does not originate in my state no matter how vague the major sites (USDA is my usual go to) seemed to be. Cup Plant has escaped throughout northern New York and New England, it is now considered invasive here. In some spots (like the Adirondack Park sited Ausable River in Keene Valley) S. perfoliatum is crowding out all the other wetland vegetation. State Biologists warn against its use in gardens.

Over the past 12 years I’ve sometimes used Cup Plant in my landscape design work. I liked it because it looks like something the first year its in the ground without fail, and because of the unique cup shape of the leaves at the stem; the perfoliate structure gives the birds a place to drink water even miles away from a source. But the nagging of the state biologists bothered me. I looked into the various articles written supporting their emerging view that in upstate New York, Cup Plant is bad news. As a few years went by I had to concede that Cup Plant is at best a bully in any place I’ve used it and at worst, may be deteriorating the habitat around the properties where I’d decided to place it. I had to ask myself- why, really- why- would I want any of my purportedly eco-supportive actions to net some kind of end result of, however slight the chance or invisible to me: incidental harm to the environment? Its hard to allow for a course correction when I’m convinced I’m set for knowledge.

I spent time this past autumn digging Cup Plant out of several gardens I manage. It was miserable. At one site the roots were so gridlocked I had to use an axe. Replacing the regionally invasives with natives though, that felt the opposite of miserable. Placing Monarda, Lobelia, and Vernonia where the Silphium had been- thats joy. I can smile now and know I’ve done okay by those properties.

I think about my trajectory with Silphium perfoliatum, my learning curve not dissimilar to a bad love affair (Just leave him! He’s no good for you!) a whole lot in discussions about invasive and non-native plants these days. The thing is theres just a truckload of nuance in the development of an invasive species. Ecologists dont know how to predict what species are going to make the jump from gardens to the landscape and it can take a long time to unfold. Japanese Honeysuckle was a benign garden plant for somewhere between 40-70 years before it became the tyrant we spend billions of dollars battling every year now. Weather aberrations like a few degrees in temperature varying, superstorms or other, weird pressures we cant imagine might just spark an innocuous non-native to rage off persistently in the landscape. We really don’t know.

When I think about the good stuff I want to do in my community for habitat restoration, and the joy I feel about good things I’ve already seen happen for the wildlife and ecosystem in my sphere of influence, now I feel a pause too. Because I know it could have gone the other way for me with Cup Plant. I could have dug in my heels, insisted I was right, refused to listen to reason and science. And inevitably other things will come up in the same realm of discourse. I dont know everything. I’m blessed to have some resourceful, well-read friends who keep up on the latest research on invasive plants and ecology. Heres what’s working in my favor- I listen with an open mind when someone who knows more than I do about a particular subject is talking. And if that subject is ecological gardening- I probably take notes when they’re talking. I really don’t want to miss anything and I especially don’t want to cause any ecological harm.