Freshly growing clump of invasive Japanese Knotweed in early spring.
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How A Garden Expert Keeps Japanese Knotweed Out Of The Garden
To learn more about Japanese knotweed, House Digest spoke exclusively with Liz Will, master gardener, garden coach, and educator at Learn To Grow Gardens.
Will notes that because the invasive species grows well in sun, shade, and even drought, they can spread extremely quickly in a way that's not easily controlled.
To prevent Japanese knotweed from entering your garden, Will says to keep an eye out for signs of new growth in the areas surrounding your property.
Will said, "Young growth resembles asparagus or bamboo shoots that are red in color." She added, "Later, the shoots become hollow stems."
Identifying and preventing them from encroaching on your property is important because getting rid of them isn't as simple as digging up the plants or cutting them back.
According to Will, "Attempting to dig up the plant can make the problem worse, as any pieces of the rhizome or stems left behind will sprout into a new plant."
If Japanese knotweed makes it into your garden, Will says patience is essential. It may take several years to eradicate the plant once it lays root.
While Japanese knotweed can survive in the shade, Will noted that it grows strongest in full sun. Completely shielding it from the sun can slow its growth.
"Covering the area with a tarp in the spring can help control a small area," she said. "Cut the stems to the ground and hold the tarp down with rocks."
She added, "Leave the tarp in place until you are sure it has withered and died. This can take an entire season, or more, depending on the size and strength of the plant."
Instead of trying to dig up or cut down the plant, Will says your best bet is simply using a weed killer, such as glyphosate, or hiring a professional to take care of it.