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Remove Japanese Knotweed Before it Harms Your Home’s Foundation

June 25, 2020

During the summer months, weeds that sprout and grow unchecked in your yard or in adjacent properties around your home can become an eyesore quickly. Did you know, however, that some weeds found throughout the U.S. can also cause harm to a home’s foundation? One of these invasive weeds that is the most difficult to remove is called Japanese Knotweed. If found, home and business owners should remove Japanese Knotweed immediately, before the fast-growing plant discovers weaknesses in concrete walkways and foundations, and makes even small holes and cracks even more costly to fix.  

Remove Japanese Knotweed Before it Harms Your Home’s Foundation
Remove Japanese Knotweed Before it Harms Your Home’s Foundation Created By: Groundworks

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Spotting This Invasive Weed

Homeowners can identify Japanese Knotweed by its tall stature and large growth span. The invasive species can grow up to six feet tall and more than 65 feet wide. It commonly grows in sunny and partly shady areas that have been cleared for homes and other construction. Japanese Knotweed has bamboo-like stems that are green to reddish-brown, depending on the season. It also has white-green flowers that grow in small, droopy clusters on its recognizable six-foot stems.

One of the reasons why Japanese Knotweed is so hard to find and remove early, before it grows throughout a property, is its fast-growing roots. The weed survives and reproduces underground from a complex, widespread root system that can cause major issues beneath a home’s yard, including degrading the soil. Unfortunately, just pulling out the visible stems won’t kill the full root system. Instead, the entire plant must be killed and fully removed to prevent new growth.

Be Aware of Property Damage

How can Japanese Knotweed cause damage to homes and yards? The weed’s fast growing, sturdy stems can grow through small cracks in concrete walkways and patios, walls, floors, and a home’s foundation. In addition, the sturdy roots can interfere with drainage and home septic systems. Landscaping can also be destroyed by the fast-growing noxious weed. Because Japanese Knotweed is known to be so difficult to fully eradicate, in some states mortgage lenders require homeowners to declare its presence on a property when selling the home.

The Removal Process

If you identify Japanese Knotweed on your property, you are in for a difficult and lengthy process to fully remove and kill the plant. Remember, if you just pull up the stalks growing above ground, the weed continues to grow out and then up from underneath the soil. A weed that can span 65 feet underground, it can be hard to find and remove the entire plant. Even a small amount of root left growing under the soil can allow it to regrow quickly.

Depending on what season you begin the removal process, here are some tips to help protect your home from Japanese Knotweed. 

In the Spring, dig up all of the underground stems and remove them from the property completely. Make sure the plant clippings are destroyed, bagged, and picked up by the trash collector. Do not add it to compost piles, store in another area of your yard, or dump it on another property. This will cause the plant to grow somewhere else, causing even more widespread damage. Finally, cover the entire area where underground stems were removed with a tarp to prevent new growth. If stalks grow up into the tarp, you can crush them from above, keeping the tarp over the full area to stunt additional growth.

In the summer, cut down the plants growing above the ground and gather and remove all cuttings, disposing of them properly.

In the fall, apply a weed killer to the entire area to prevent growth the next year. Remember -- to fully remove the weed and prevent new growth -- you must cut down and get rid of the entire plant’s stalk growth, throw away all of the clippings, dig up all underground stems within 20 feet of the visible stalks, and smother new growth with tarps over the area. In the fall, apply a weed killer to fully eradicate the weed.

Finally, if you find Japanese Knotweed on your property, contact a professional to inspect your home’s foundation, crawl space, and basement to ensure that the weed has not caused damage to your home. Cracks caused by the invasive weed can produce leaks in the basement and crawl spaces and invite pests. Allowing moisture into the home can cause mold and mildew growth.