Taking Back the Yard: Dealing with Invasive Plants

Wednesday, June 12, 2013

There’s nothing more frustrating for gardeners than discovering that their well-planned plots or rolling lawns have been infiltrated by invasive plant species, the perennial marauders of the back yard set. While many people panic and immediately start yanking or mowing the intruders when they first make their appearance, gardening expert Karen Snetselaar, Ph.D., chair and professor of biology at Saint Joseph’s University, advises that it’s best to investigate the plant that’s choking your columbines or blighting your lawn before complicating the problem with an errant course of action.

“Education is key,” Snetselaar says. “Find out what it is that you’re pulling from the ground. Knowing more about the invader will help you make better choices, and it’s less likely that  you’ll be responsible for the proliferation of an invasive species.”

According to Snetselaar, there are great online sources to consult, and each state’s department of natural resources will typically provide information about problem plants. In addition, the National Park Service’s Weeds Gone Wild site has a manageable list of factsheets for some of the most common invasives.

Timing is critical for removing the more pernicious trespassers, says Snetselaar. Japanese stiltgrass (Microstegium vimineum) is a prime example. A weed that is spreading rapidly in the Mid-Atlantic States, this Asian native is dispersed by seed and grows prolifically in lawns. While it’s tempting to fire up the lawn mower when it’s detected, Snetselaar says that if it’s mowed, the stiltgrass will just produce seeds on tiny little plants. “It’s better to wait until the grass matures a little — not to the point where it’s actually making seeds, but just before that stage — and then pull it up by the roots.”

On the other hand, Snetselaar notes, pulling up Japanese knotweed (Fallopia japonica), a notorious invader, isn’t recommended, because it can re-grow from even the tiniest bit of root. Herbicides and repeated cutting and bagging of the stems are the prescribed approaches. 

Invasive plants are likely to keep most of us busy for a long time, Snetselaar says, and factors that we can’t control, such as climate change and stormwater runoff will continue to result in new invasions. But though they may present many thorny problems, it’s not inevitable that the invasive plants will win. It’s critical that homeowners take the time to consider how to make their lawns and gardens less susceptible to invasion, she says.

“Clearing everything from a weedy spot in the yard can be cathartic, but unless you have a good plan for what will take the place of what you remove, a slower approach is advised, or you’ll just prepare the ground for a new invasion,” Snetselaar says. Gradually removing aggressive plants and replacing them with better-behaved species takes patience, she adds, but in the long run, homeowners are rewarded with lovely gardens and healthy lawns.

Snetselaar, a trained botanist, can be reached for comment at 610-660-1826, at ksnetsel@sju.edu, or by calling the Office of University Communications at 610-660-3240.



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