The Georgia Exotic Pest Plant Council has listed more than 100 non-native invasive plants in our state. All of them pose threats to our natural areas.
The Japanese knotweed, listed as a Category 1 Alert, is not yet widespread but is a significant threat and is becoming a serious problem. Where found, this invasive plant causes the most damage to homes, breaking up foundations, driveways, walkways, and patios. It finds any cracks or weak spots, growing through them, expanding, and causing still more damage.
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What Is Japanese Knotweed?
The Japanese knotweed can grow up to three inches per day, can reach 10 feet tall, and the roots can grow as much as 20 feet deep. On top of that, the rhizomes can spread up to 70 feet from the nearest stem. Then there is its ability to regrow from as little as a half-inch segment of stem.
It has the distinction of being listed in the Top 100 World’s Worst Invasive Alien Species. It can grow. It can spread. And that makes it very difficult to eradicate.
How To Identify Japanese Knotweed
The stem is hollow, green with purple speckles, and has swollen nodes that give it a bamboo-like appearance. It grows from three to 10 feet tall.
The Japanese knotweed leaves are bright green with purple speckles, growing up to six inches long and five inches wide. They are heart-shaped and grow in a zigzag fashion 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, at Knotweed Help.
Damage From Japanese Knotweed
In the wild, the Japanese knotweed crowds out native plants by forming a thick layer of stems and leaves that literally puts them in the shade. The weed also releases a toxic chemical that inhibits the growth of nearby plants.
Near our homes, the roots find cracks and joints in drainpipes, clogging and even splitting them. They also find cracks and any openings in home foundations, widening them, bringing moisture and all the damage that causes.
They can also grow underneath concrete and asphalt driveways, sidewalks, and patios. They find weak spots, grow through them, and break up the paved surface. They can do the same thing with retaining walls.
The Japanese knotweed’s spread causes huge economic damage. 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.
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
As you can imagine, 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 with a tarp to eliminate light and water, and 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 in order to remove every bit of root. You can also try a glyphosate-based herbicide, the main ingredient in Roundup. All these approaches take time and considerable effort.
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
If you find Japanese knotweed on your property, contact the professionals at AquaGuard Foundation Solutions for a free inspection to ensure the weed has not caused damage to your home.