Invasive plants aren’t just weeds you pull up and forget about. Invasive plants are quick-spreading species that edge out your garden’s flowers and any native plants. Pulling some of these species up is actually the worst thing you can do, as it is an excellent method for distributing the invasive plant’s spores.
Expert gardeners know to locate and identify any invasive species in the landscape before they start weeding. If you aren’t a horticulturalist who can name non-native plants on sight, take a picture of any suspected plants, as close-up and in focus as possible. Load that image into a browser image search like Google Images. You may find a match there. If not, head over to a local nursery with your pictures. The experts there will be able to identify the plant and tell you what kind of sprays to use to eradicate it.
Jim Culley, Account Manager for Anewalt’s Landscape Contracting in Berks County, PA, sees a lot of invasive plants in the over 4 million square feet of landscapes the company services. Jim suggests homeowners do their research on invasive plants. Find lists of invasive plants and information on resource sites like Pennsylvania’s Department of Conservation and Natural Resources (or search for your state’s department) and The United States National Arboretum.
The most prevalent plant Anewalt fights off is called Canada Thistle. “It can get into grass, mulch beds, and farmers’ fields,” Jim said. “It’s full of thorns so predators like deer won’t eat it.” Also known as Canadian Thistle (with proper name sci cirsium arvense), this flowering perennial weed shouldn’t be pulled up. “It just says, ‘thanks for pruning me!’” Jim joked. “It’s best to spray it with a selective herbicide when it is actively growing. That’s in spring, in Pennsylvania around May or June, when it is about 12 inches high.” Jim says to ask at a local nursery for an herbicide that can “translocate” down into the root. The leaves, once sprayed, will absorb the chemical and then carry it down into the root system where it kills the plant. A typical Round-Up spray homeowners tend to buy doesn’t contain the translocating chemicals needed to kill Canada Thistle. Make sure to buy the right spray for the invasive species you have in your lawn.
“Thistle is one of the most difficult things to control in our beds,” Jim said. Jim said that other weeds need to be contained too. Watch out for Hairy Bittercress (proper name cardamine hirsuta), an annual weed from the mustard family. These seed pods ripen and pop and can throw the spores flying as much as 16 feet away. This one you can pull up. “The trick is pulling it early in the season before it sets the seed. Do this in the fall, before labor day. Use the herbicides that prevent germination,” Jim said. Another invasive plant Anewalt sees often is Japanese Barberry (persicaria perfoliata). “It’s also called ‘mile-a-minute.’ It’s a vine that can literally grow a foot a day.”
Jim suggests homeowners also check out the Ecological Landscape Alliance website, which has a lot of information on identifying and managing invasive species. The sites lists fact sheets on various “exotic” plants.
“Scouting is one of the most important things,” Jim said. “Look and identify.” Catching the spread early is the least expensive way to battle these invaders. Once an invasive plant has spread, it can take a lot of labor and materials to get it under control. If you keep an eye out for these species and keep a cool head, your landscape will be free to grow beautifully.
TIP: Will weeds grow between my pavers? To learn how to prevent them visit EP Henry’s FAQ page under pavers.