4 Japanese Knotweed Removal Strategies (And Why You Should)

Japanese knotweed is in the order Caryophyllales and the family Polygonaceae. The plant’s scientific name is Polygonum cuspidatum, but it is sometimes called the Godzilla weed or Japanese bamboo. It is a plant native to East Asia but was brought into the United States in the 1800s. Unfortunately, it can be highly invasive, even growing up through cracks in the concrete and choking out other plants a homeowner may want to keep. 

Why Should You Get Rid of Japanese Knotweed

If a garden has Japanese knotweed, is it something to be concerned about? The perennial plant doesn’t die off after a season, but grows thicker and more prevalent over time. The roots of the plant grow horizontally and can spread 34 feet rapidly. 

There are many issues with Japanese knotweek, including its ability to degrade wetland quality and destroy riparian habitats. Thickets of the plant grow dense enough to prevent other vegetation from growing. Some additional issues with knotweed include:

• Reduced native plants 
• Fewer amphibians, birds, reptiles and mammals in the area 
• Roots could alter soil chemistry 
• Damages concrete and housing structures 
• Creates soil instability, which can lead to erosion and mudslides 
• Can block access to waterways for human use

On the flip side, Japanese bamboo does have a few beneficial properties. The plant contains a compound known as resveratrol, which has high antioxidant activity and may improve heart health. People can eat the plant’s new shoots in the early spring, so it provides a potential food source. 

While a well-contained Godzilla weed patch can provide ground cover and grows well, unless one is certain they can contain it, the plant should be removed before it grows out of control. 

Top Ways to Remove Japanese Knotweed

Homeowners will find there are a number of effective ways to remove Japanese knotweed from their properties. Although the roots tend to be shallow, they can grow six feet deep, making it difficult to get rid of the plant, so homeowners must be as tenacious as knotweed. Most homeowners are worried about the biodiversity and wildlife in their area and will opt to stay away from harsh chemicals that might damage the local ecosystems. Thankfully, there are other options. 

1. Herbicides

Herbicides are one of the most effective ways to kill out the weed. The best time to apply is in late summer or early fall. Multiple applications are typically needed. To kill Godzilla weed, choose an herbicide with glyphosate. Read the label of any weed killer to choose the right one. 

Wear gloves and be aware of the potential impact on the garden and surrounding habitats. Because the plant is so invasive, it’s extremely difficult to get rid of it without using herbicides. Talk to the local garden center for additional information about the best products to use on the plant without causing environmental damage.

2. Cut Back and Burn

Another option that won’t fully eradicate the plant but can contain it a bit is to cut it back in the spring and fall and burn it. Be careful as trying to remove Japanese knotweed with fire can result in a stronger thicket that refuses to budget. The roots will grow deeper and stronger over time.

Cutting and burning may work best when fully removing the root system, but one may have to dig pretty deeply to get all remnants of the roots out of the soil. 

3. Remove the Roots

Although not the easiest solution to getting rid of Japanese bamboo, removing the roots may be the most environmentally friendly option for land owners. Start by finding the rhizome clumps. Dig up as much as possible.

For more established plants, a backhoe may be needed along with the help of a professional who knows how to remove the invasive species so it doesn’t return. Completely bag and dispose of the plants and their pieces as a tiny shoot can turn into new growth and force the homeowner to start the removal process over again. 

4. Smother the Plant

Start by cutting the shoots down as far as possible. Spring and fall are both good times to repeat the process. Once the plant’s stalks are cut down, cover the area with a heavy tarp. Check again every three months, cut the shoots close to the soil and cover the patch back up. The goal is to weaken the rhizomes by removing the sun it needs to thrive. 

The tarps should go out five to ten feet past the cleared area. Put bricks, blocks or rocks around the edges to hold it down and prevent any knotweed from escaping and any sun from making its way inside.

According to The Spruce, it takes about five years for the weed to die completely. After this time, one can safely remove the tarp and replant the area with grass or different plants. 

How NOT to Remove Godzilla Weed

Be extremely cautious when cutting down the plant. Little bits are easily flung elsewhere in a yard or a neighbor’s yard, causing new shoots to appear around the area. The plant is extremely invasive, so a neighbor who doesn’t know what they’re dealing with may allow the problem to spread right back to the original yard or into other neighborhood areas. 

Some people try methods such as smothering the plant with lime, dousing it in bleach, spraying it with salt or pouring fuel on it. Experts caution that these methods are not effective against Japanese knotweed and will harm your yard and the local biodome.

Never plant an invasive species such as knotweed or bamboo. Master Gardener Alyssa Ford Morel offers some alternatives to invasive plant species, such as the Carolina Jessamine vine or evergreen hedges.

Be Persistent

Many gardening experts believe removing Japanese knotweed works best when one takes multiple approaches at the same time. However, for people trying to avoid the use of chemicals, patience may be the answer. The invasive knotweed will hang on to life until the last possible minute. To rid a yard of the plant, one must form a plan of attack and remain consistent in their efforts. Eventually, the knotweed will go away and a beautiful, lush lawn will return.