Why Should I Worry About Japanese Knotweed?

The two words that send shivers down the spine of any property owner – Japanese Knotweed is classified as an invasive plant in many countries.

It’s a plant which can seriously damage buildings and construction sites if left unchecked. It has a wide-ranging root system, which can extend up to 3m in depth and 7m in all directions. These can pose a serious threat to construction works and have devastating consequences to building foundations and drains.

If you are found to be failing to stop the spread of the plant, you can be issued with an Antisocial Behaviour Order – an ASBO. Under these orders, you could be fined up to £2,500.

The plant has hollow stems with pronounced nodes, giving it a similar appearance to bamboo. However, knotweed isn’t related to bamboo and is a closer relative to buckwheat. The plant can grow to 4 metres tall and produces broad leaves.

Japanese Knotweed

Stockport’s Commercial Property Experts, Fairhurst Estates, explain more: 

What is the issue?

The problem with knotweed arises when it is introduced to an urban setting. The plant develops massive root systems that regularly extend 3 metres down and 7 metres wide. These roots can ruin building foundations, drainage systems, and even roads.

Knotweed natively grows around areas of volcanic activity in Japan, where the plants are naturally kept manageable due to elevated levels of ash in the soil. When these plants take hold in more inviting British soil, however, they can grow as much as 20 cm in a single day.

This wouldn’t be an issue if the plant wasn’t so prodigious at spreading. While Japanese knotweed doesn’t produce seeds, even a tiny piece of rhizome (the underground stems of the plant which produce roots) can sprout a whole new plant.

If you thought that dealing with weeds such as dandelions was a pain, knotweed is in an entirely different league. Knotweed rhizomes are incredibly resilient. They can survive temperatures as low as -35^oC and other usually inhospitable conditions.

Since knotweed spreads so quickly and is so difficult to get rid of, it can become a major problem for businesses and homeowners alike. Some homeowners have seen the value of their property nearly cut in half due to the presence of this weed.

Some UK lenders have even refused mortgage applications when Japanese knotweed was discovered on the property, although such restrictions were controversial and have since been loosened. The stress of dealing with knotweed can be so overwhelming that one West Midlands man was tragically even driven to suicide.

What to do about it

At present, the government has no plans to eradicate Japanese knotweed, as it would cost an estimated £1.5 billion to accomplish. Removing knotweed from the site of the London Olympic Games alone had an associated cost of £70 million.

Although knotweed is an extreme nuisance, there are some steps you can take to destroy it. Knowing the right steps to take is important, but you should also be aware of what not to do. Disposing of knotweed in regular household waste or dumping it off-site is illegal and taken very seriously by environmental authorities. It can result in a fine of £5,000 or two years in prison. When disposing of knotweed at an off-site disposal facility, the owner of the site must have a specific permit that allows for the disposal of invasive weeds.

Chemicals can be used to treat knotweed infestations. Don’t expect to completely remove the knotweed in one spraying though. On average it takes about three years of treatment to force the plant’s rhizomes into a dormant state.

Burying knotweed is not a practical solution. Even when buried metres underground, Japanese knotweed can still find its way back to the surface.

Burning knotweed is another disposal option. Individuals can burn the waste privately, but businesses must inform the Environment Agency and their local environmental health officer before burning Japanese knotweed themselves. Knotweed rhizomes can sometimes survive burning, so it’s recommended to either bury or dispose of the remains off-site even after the plant has been burned.

Be vigilant about Japanese knotweed

Japanese knotweed can be an absolute nightmare for both businesses and homeowners. Once your property falls victim, it can be difficult to get rid of. Catching the problem and treating it early is your best option, but the options above can help even if your land has already been compromised.

Expert Opinion article contributed by Fairhurst Estates