We’ve all heard stories of non-native or invasive plants and the environmental havoc they can cause. They’re often difficult to get rid of, but we’re encouraged to try anyway; if you feel like clearing out a patch of kudzu, no one is likely to stop you. If you’re feeling especially adventurous, you can even eat it. The roots can be used to make tea and the flowers to make jelly.
Not all plants are so harmless, though. Recent reports from Virginia describe a large plant—taller than a person, with five-foot-wide leaves and huge white flowers—that fights back with a vengeance when homeowners try to remove it. The plant, known as giant hogweed (Heracleum mantegazzianum), is toxic; touching the sap can cause burns, and getting it in your eyes can temporarily blind you.
Some county officials in Virginia are issuing warnings to help people identify the plant—it looks similar to and is easily mistaken for the much more common native cow parsnip, only bigger—and to caution them about its potential effects. The sap can cause blisters, especially if contact is followed by sun exposure. “Your skin can remain sensitive to sunlight for many years after exposure as well,” one county warning notes.
Giant hogweed was imported to the US from Southeast Asia just about a century ago as an ornamental plant. Many other species, though, have been brought in to control erosion. Kudzu is one of these; farmers once actively planted the stuff, and it has spread throughout large parts of the country, driving out native plants as it goes. (Trivia fact: During World War II, American soldiers stationed in the Pacific used kudzu as camouflage for airfields. It has since practically taken over the small island nation of Vanuatu. Locals have given up trying to control it and are now harvesting it to make “Hempcrete,” a bio-composite building and insulation material.) Tamarisk trees were similarly imported to the US for use as windbreaks and to control erosion, and they too have disrupted many native habitats.
Introducing a plant to a new environment is almost always easier than eradicating it. A few years ago the Department of Agriculture tried releasing salt cedar beetles to kill tamarisk trees in Colorado and Utah, with some success. We haven’t found an effective way to control kudzu. In the few states where giant hogweed has appeared—New York and Maine, in addition to Virginia—state agencies or university extension programs have been sending out hazmat-suited specialists with goggles to handle individual plants. There might be a simpler solution, though: eating it. Cows and pigs can munch on it without problems, and it has even been planted in some cold European climates as cattle fodder. Just as we’ve used herds of goats to control buckthorn and other invasives without herbicides (see the article in the October 2017 Stormwater), we might soon see herds of cows turned loose to tackle the 10-foot-tall giant hogweed.Have you had to remove non-native plants during restoration or landscaping projects? What do you think of using biological controls—from beetles to goats—to control them?