13/06/2024
Black Swallowwort.
Repeating what I've said in the past, that non-native, invasive Black Swallowwort is a menace in many ways, including that it results in the death of Monarch Butterflies. If you want to kill the existing plants, in addition to preventing their spread, then your time to act is NOW.
Killing the plants is difficult. Pulling or mowing doesn't kill them. If you have a random few plants, you can try to dig them up, but their stringy roots break easily and leftover root pieces can grow new plants. If they're growing on a fence or a hedge, digging up the roots becomes very difficult to do successfully. Using homemade recipes like vinegar will not work.
Using an appropriate herbicide in an appropriate (ie, limited) fashion can get the job done in one pass. Wait until the plants are flowering (many are flowering now, early June) before using herbicide. Use prior to flowering will be less effective. It is easy to miss the very small, dark colored flowers, so before dismissing them as not having flowered, look closely.
Use glyphosate at 2% to 5% concentration or triclopyr at 1%. (That is according to URI) These herbicides will kill most plants they hit, so if your swallowwort is growing among a hedge or other plants you want to save, or if you want to be more judicious with your herbicide use (always a good idea), using a "glove of death" is a good option.
Glove of Death. As above, proper and limited use of herbicide is safe. Using a Glove of Death is about as limited and directed as one can get.
Find yourself a glove that will prevent herbicide from getting on your fingers, such as heavy duty kitchen dish washing gloves. Put an inexpensive cotton work glove on top of that.
Now, moving slowly and carefully, spray your gloved finger tips or dunk your gloved thumb and pointer (or whichever fingers you'll use) into a small container of herbicide, squeeze the fingers together to get rid of excess liquid that might spill on other vegetation, and caress the leaves of the plants you want to kill. If you purchased a spray bottle, you can carefully spray the tips of the fingers you'll be using rather than dunking.
Be sensible. Wear long pants and closed toe shoes. This is not a time to wear flip flops. If you're spraying, wear eye protection. This method works well on many invasive species (at appropriate times!) and dramatically reduces herbicide use.
After applying the herbicide wait 2-4 weeks before pulling the plants or just let them die in place.
"Cut stem application" is another great method that is very directed and limits use of herbicide, but it doesn't work very well on Swallowwort.
Photo on left are swallowwort pods collected in Arlington. Photo on right is what the plants look like right now, with tiny black flowers on the vines.
You can see more information and photos by googling "swallowwort control site:*.edu" and here: https://www.facebook.com/AlliumFields/posts/pfbid0AkykuCJocNBUNC1E9bbHGHXomyMs7bJDk3WpFdghmftQKMckz9LbvXzpqCdv9Ze1l
