I knew as I was ripping up Swallowwort that I needed to know what should replace it. Which beach weeds were going to be the next invasive problem, or which weeds were perfect native replacements? I just didn’t know.
I’ve been studying plants for 20 years, inheriting the interest from my mom, but had never paid any attention to native vs. alien, or what was invasive.
I found most internet sites lacking, but have been able to cobble together the info I want. I found a pdf booklet Mistaken Identity, which shows some common invasives and native look-alikes, but which is very limited to about 20 pairs. This limitation is the biggest problem with most invasives guides, whether pamphlet, live online or in pdf format. The NYS site has only seven priority species and doesn’t include Swallowwort. I see this weed almost everywhere I go.
But that site did have a pdf ranking of 183 alien species and their invasiveness, and that has been pretty useful, though I’m still not sure it’s complete. The problem may be that while alien vs. native seems to be a straightforward distinction without much debate, invasiveness is more subjective and must differ from place to place. Does the plant take over, or does it play nicely with others? Does it put out its leaves so early that it can outcompete everything else? Does it use chemical means to suppress competition? Is it a smothering vine? These are all measures of how it impacts diversity. Another question is its impact on wildlife; does it put out berries or nectar less nutritious than what it replaces? No food at all? Branches so stiff that snakes can reach bird nests? Dense mats that leave no room for cover? Other negative effects? It takes a lot of field research to answer questions like these, and you can never be sure you’ve covered every habitat.
I have those two online resources to help me, along with a few small brochures which only cover a handful of species but give good details on why the weeds are a problem and what to do about them.