It’s been described as “breathtaking” when it’s in bloom, but the Japanese knotweed is not the sort of ornamental plant you want to cultivate in your yard. And really, it’s only ornamental when it flowers in summer, but it’s an invasive pest all the year round.
Believe it or not, the plant is so hardy and aggressive that it can even prove a threat to home foundations, and it’s been spreading through the midwest, northwest, and northeast quadrants of the United States.
Japanese knotweed is a kind of shrub that first arrived in the U.S. in the 19th century. You’ll be hard pressed to find a plant that grows faster; the knotweed can grow up to three feet in a single week, and has stalks that appear similar to bamboo. The plant is thought to be impossible to eradicate by any known means, and it likes to dig into cracks in tough man-made materials like asphalt or concrete (there goes your home’s foundation).
Robert Naczi is the curator of North American Botany for the New York Botanical Garden. He said that just a tiny piece of root can turn into a fully grown Japanese knotweed, and the plant seems to be able to thrive in just about every soil and weather condition. He said “you have to respect this plant” which grows so fast in spring you can almost see it as it adds inches per day. The largest specimens have been measured at 15 feet tall.
UK homeowners are wise to the garden pest, too. In fact, UK law requires homeowners to disclose to sellers whether the weed is found on the property, and homeowners can be prosecuted if it jumps boundary lines. Apparently some firms even offer an insurance plan to do maintenance on the plants (remember, it can’t be eradicated).
Homeowners might want to seriously worry about the plant’s effect not only on their yards and structures, but on the resale value of the property. One couple from Maine told the Wall Street Journal they’ve battled the invasive species for years to no avail, and they worry about what it has done to the value of their home.
What can you do about it? It can be slowed down but it takes a lot of work. Experts advise keeping it mowed, and to dig up the roots. Others say it should be chopped down and the roots treated with herbicide, but nothing is guaranteed to get rid of the hardy plant.
