The Alabama Invasive Plant Council’s list of invasive plants shows Japanese knotweed in the watch category, with 10 counties reporting infestation. The Tennessee Invasive Plant Council classifies it as a severe threat with infestation in 24 counties. There are even news reports from Knoxville stating that it is actually overtaking kudzu.
While there are other invasive and noxious weeds in our area, it’s Japanese knotweed that threatens home damage. It finds cracks or weak spots and grows into and through them, damaging foundations, driveways, sidewalks, and patios.
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What Is Japanese Knotweed?
Japanese knotweed can regrow from a mere half-inch segment of stem, root, or rhizome. It also has an underground network of rhizomes that can spread up to 70 feet from the nearest stem. Roots can grow up to 20 feet deep and the stem can grow as much as three inches per day, reaching between three and 10 feet tall.
All that helps it take over large patches of territory and makes it extremely difficult to eradicate.
How To Identify Japanese Knotweed
The stems that closely resemble bamboo, along with its attractive flowers. The stem is a hollow segmented cane that’s green with purple speckles. The leaves are bright green with purple speckles, heart-shaped, and grow staggered along the stem.
Creamy greenish-white flowers form in clusters up to four inches long from late August through September.
You can find a comprehensive guide to identification, including a video guide, at Knotweed Help.
Damage From Japanese Knotweed
Root growth from the Japanese knotweed represents one of its biggest threats. They spread underground, find drainpipes and foundations, and enter cracks and weak spots, causing considerable damage.
They also grow under driveways, sidewalks, and patios. Finding the weak spots, the stems grow up through them seeking sunlight. They can further damage stone or brick retaining walls, breaking them up and causing collapse.
The weed’s spread causes a huge amount of economic damage. As just one example, since 2010, New York City has spent more than $1 million on eradication efforts for a 30-acre patch of Japanese knotweed.
If it finds its way into your lawn, it can also impact your home’s resale value. That’s on top of the cost of repair and eradicating the weed.
How To Protect Your Home
Getting rid of Japanese knotweed is extremely challenging. There are several steps you can follow that include: cutting the stems, removing the clippings, covering the area to eliminate light and water, then placing a plastic barrier in the soil around the area to stop root spread.
Another option is to excavate the entire area, at least to a depth of 20 feet. You can also try a glyphosate-based herbicide, the main ingredient in Roundup. All these approaches take time and considerable effort. Plus, there are a few long-lasting effects from either the herbicide or the excavation.
You can also consult an expert in eradicating knotweed who has the expertise and experience to remove the plant without spreading it elsewhere in the process.
We Can Help
We’ve helped homeowners with foundation damage from plants, trees, weather events, and shifting soil from our offices in Birmingham, Huntsville, Mobile, Nashville, Chattanooga, and Knoxville.
If you find Japanese knotweed on your property, contact the professionals at AFS Foundation and Waterproofing Specialists for a free inspection to ensure the weed has not caused damage to your home.
