Connecticut homeowners looking to attract more birds and pollinators to their yards are told to grow more native plants and eliminate the invasive ones.
“An invasive plant by definition has to be something that was not evolved in Connecticut,” said Lauren Kurtz, an invasive species outreach specialist at the University of Connecticut.
Kurtz said invasive plants are bad for the local ecosystem for a variety of reasons: they out compete and choke out native flora, they don’t provide a food source for native wildlife, and in some cases, like black and pale swallow-worts, they can even be poisonous to moth and butterfly larvae.
One of the ways an invasive species can prevent the growth of native plants is a biological phenomenon called allelopathy.
“That is the ability of a plant to give off a substance, either through its roots or through its leaves, that inhibits other plants — except its own kind — from growing near it,” said Michael Nadeau, owner of Wholistic Land Care Consulting.
Nadeau says the invasive garlic mustard plant is a common species with allelopathic abilities. According to The Nature Conservancy, it can release chemicals which impact the growth of trees.
The Connecticut Invasive Plant Council maintains an official state list of which plants are categorized as invasive, which experts say is important for gardeners to follow.
“Be aware of plants that are invasive in your state,” Kurtz said, “because some of them still can be sold in the nursery.”
But Connecticut gardeners likely know firsthand that invasive plants don’t have to be bought — they just pop up one day, spread by the wind, wildlife and other natural means.
“It's a deal that native plants have made with native fauna for eons,” Nadeau said. “But now that these new plants have been introduced from elsewhere, they're taking advantage of the same methods of spread.”
How to identify invasive plants
One of the hardest tasks for homeowners in fighting invasives might be in correctly identifying them.
Take, for example, the vine of the black and pale swallow-wort. It can look very similar to the native Cynanchum laeve, which is actually beneficial to butterflies, according to the Monarch Joint Venture.
Since most of us cannot go back to college and get a botany degree, Kurtz said that’s where cell phone apps can come in handy.
Kurtz highlighted free options available such as Seek, Picture This, and Google Lens. But she warns those apps can’t guarantee 100% accuracy, so she also recommends the website Go Botany which is run by The Native Plant Trust.
How to get rid of invasive plants
Human action is required to get rid of invasives because, as Nadaeu points out, “they don't have any natural checks and balances.”
Some plants don't even need seeds to regrow. An invasive plant like Japanese knotweed or multiflora rose will grow back from a stem cutting, according to Kurtz.
To limit the spread, Nadeau and Kurtz both recommend the “solarizing” approach. That involves ripping out the invasive plant from the ground and using the heat of the sun to kill the plant before disposing of it.
“I usually put them in a black contractor's bag and sit them in the sun … for like a month,” Nadeau said.
Kurtz recommends placing the plant on top of a tarp in the driveway, as long as the plant can’t be blown away.
Ensure any plant that has gone to seed is truly dried out before it can be discarded in the woods or a lawn bag, Kurtz said, otherwise it will just sprout in its new location.
When dealing with an established invasive vine, bush or tree that cannot be completely ripped out of the ground, targeted herbicide use can be an option, according to Nadaeu and Kurtz.
But Nadeau cautioned “there's no one size fits all” when it comes to using an herbicide. What time of year to apply it and what kind to use depends on the plant. He recommended following the guidelines released by Connecticut Invasive Plant Working Group.
After ripping out an invasive plant, Nadeau “strongly recommends replanting that area with an aggressive native plant.”
Be careful what you buy
Nadeau advises homeowners to buy from nurseries that grow straight species, rather than cultivated plants that have been crossed with another plant to “get some kind of characteristic that humans like that they think will make it sell better at the nursery.”
“The problem with cultivars is that a lot of the native fauna does not recognize it,” Nadaeu said.
For example, bees might shy away from certain buds.
“A cultivated Black Eyed Susan gets no visits from pollinators. The straight species gets mobbed with pollinators,” Nadeau explained. But the cultivated Black-eyed Susan is larger and showier and so it’s more attractive to consumers.
Nadeau said consumers can recognize a cultivated plant by looking at its plant tag. The Latin name of the plant will be followed by a commercial name.
A list of nurseries which sell native plants can be found at UConn and via Pollinator Pathway.
The invasive battle requires constant vigilance
“They’ll always be a seed you’ll miss. Squirrels will come by with seeds stuck to their fur,” Nadeau said.
With invasive plants, he said, it’s never a one-and-done removal process.
“Some of these plants have been here for centuries,” Kurtz said. “They've been brought to New England with some of the first settlers that ever came here. So complete eradication in the state is just not likely.”
But, Kurtz said, “do what you can on the land that you manage because that will make a difference.”
