Japanese Knotweed: What It Is, Why It Matters, and How to Get Rid of It
Japanese knotweed is a tough, fast‑growing plant that looks a bit like bamboo. It first arrived in the UK as an ornamental garden plant, but it escaped and now spreads on roadsides, riverbanks and private gardens. Its roots can break concrete, damage walls and make land hard to sell. If you see it growing, you’re probably looking at a serious problem that needs quick action.
Spotting Japanese knotweed
Typical knotweed stalks are hollow, green and can reach up to three metres tall. Leaves are heart‑shaped, glossy and have a slightly pointed tip. In late summer the plant produces clusters of tiny white flowers that smell sweet. The biggest clue is the extensive underground rhizome network – a thick mat of roots that can be several metres deep. If you find any of these signs, treat the whole area as knotweed until you’re sure it’s gone.
How to control and remove it
The easiest way to kill knotweed is a professional herbicide treatment. A licensed applicator will spray the leaves during the growing season, allowing the chemicals to travel down the roots. You’ll usually need at least three treatments spaced a few weeks apart. For a DIY approach, you can dig out the plant, but you must remove every piece of root. Missing even a small fragment can cause the plant to grow back.
Another option is to cover the knotweed with a thick, light‑blocking tarp for two years. This method starves the plant of sunlight and eventually kills it. The tarp must overlap the edges by at least 30 cm and stay in place during heavy rain. Combine the tarp with a herbicide for faster results.
After the plant is dead, you should cut the area into small pieces and have them disposed of as hazardous waste. Most local councils treat knotweed as a controlled waste, so you’ll need a certified waste carrier to take it away.
Legal considerations are important too. In England and Wales, it’s illegal to plant or cause knotweed to spread. If you’re buying or selling a property, you must disclose any knotweed issues. Failure to do so can lead to costly legal battles and a drop in property value.
Prevention is the best defence. Keep the ground around your garden tidy, remove any new shoots as soon as you see them, and avoid planting knotweed in containers that could escape. If you’re unsure whether a plant is knotweed, take a clear photo and show it to a local arborist or a plant‑identification service.
In short, Japanese knotweed is not something to ignore. Spot it early, act fast with herbicide or removal, follow disposal rules, and keep an eye on your property to stop it from coming back. With the right steps, you can protect your home, your wallet and the environment from this invasive foe.
Kieran Lockhart, Jun, 2 2025
The 140-year-old pub in Chadderton has bumped into a major hurdle on its way to becoming a new convenience store—Japanese knotweed. This invasive plant's aggressive spread is delaying the project and driving up costs for developers.
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