Japanese Knotweed: Top Weed for Home Damage in Missouri

This invasive plant, Japanese knotweed, can cause damage to your Missouri home. Learn how to identify it and how to protect your home.

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The Missouri Invasive Plant Task Force keeps a listing of 142 invasive plants ranging from trees to vines and grasses to weeds. On top of that, the Missouri Department of Agriculture publishes a noxious weed list covering thistles, vines, grasses, and other species. 

Many, if not all, do serious damage to our environment. One of the worst in terms of potential damage not only to the environment but to our homes is Japanese knotweed.

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What Is Japanese Knotweed?

Japanese knotweed is fast growing above and below ground. The stem can grow as much as three inches per day and reach up to 10 feet tall. The roots can grow up to 20 feet deep. The rhizomes can spread up to 70 feet from the nearest stem. Not only does it grow fast, but it can regrow from a stem or root segment as small as one-half inch.

When it’s growing in your yard, it can damage home foundations, driveways, walkways, and patios. It finds any cracks or weak spots, growing through them gradually expanding and causing still more damage.

How To Identify Japanese Knotweed

Japanese knotweed’s stem is a hollow segmented cane that resembles bamboo. It’s green with purple speckles. The leaves are bright green and heart-shaped, also with purple speckles, and are staggered along the stem. The plant sheds its leaves as the weather gets cold.

Creamy 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

All that root growth, both wide and deep, can find drainpipes and home foundations. They enter cracks, widen them, and start splitting the pipes and adding still more damage to foundations.

Plus, they don’t stop there. They grow underneath concrete and asphalt as well as find their way into stone or brick retaining walls. They find weak spots and cracks, expanding them and causing quite a bit of damage.

This invasive weed’s spread causes a huge economic cost. As only one example, since 2010, New York City has spent more than $1 million on eradication efforts for a 30-acre patch of Japanese knotweed.

That’s the cost of eradicating the weed. It doesn’t take into account the impact on a home’s resale value. Then there’s the cost of repairing the damage to a home’s foundation, concrete, and lawn.

How To Protect Your Home

As you can tell, eradicating 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 underground around the area to stop root spread. 

Another option is to excavate the entire area to at least a depth of 20 feet to catch all the roots. You can also try a glyphosate-based herbicide, the main ingredient in Roundup. All these approaches take time and considerable effort.

It may be best to consult an expert in eradicating knotweed who has the skill and experience to remove the plant without spreading it further in the process.

We Can Help

We’ve worked on foundation damage from plants, weather events, and shifting soil from our offices in Kansas City, Moberly, Springfield, St. Louis, and Des Moines, IA

If you find Japanese knotweed on your property, contact the professionals at Foundation Recovery Systems for a free inspection to ensure the weed has not caused damage to your home.