Japanese knotweed is an invasive plant that can be difficult to remove from your garden. It’s seen as one of the most difficult garden weeds to deal with in the UK and can cause problems for homeowners who want to sell their house. There’s legislation in place to control the weed and prevent it from spreading.
With our guide, you can easily identify and get rid of Japanese knotweed from your garden.
Why is Japanese knotweed a problem?
Japanese knotweed can sprout from a tiny section of root and spread quickly throughout your garden. It will overtake all other vegetation and can even damage eco-systems. The roots can grow to 1m deep, making it very tough to remove by digging it out.
It’s illegal to allow Japanese knotweed to grow in the wild, whether you let it escape the boundaries of your garden or if you dump it anywhere that isn’t a licenced landfill site. It’s not illegal to have Japanese knotweed in your own garden, but it’s best to start the process to eliminate it as soon as possible, to prevent it from growing elsewhere.
As well as endangering other plants, Japanese knotweed can also damage your property. It can grow through cracks in walls, in drains and even in roads. Once it has found a weakness, it will widen the gap as it grows through it, causing more harm. Since 2013, homeowners are required to declare if Japanese knotweed is present if they want to sell their house. They will also need to provide details of the plan to remove it. Buyers can struggle to get a mortgage on a property that has Japanese knotweed and will also need to provide proof that an eradication plan is in place.
How to identify Japanese knotweed
Japanese knotweed is a perennial weed, so it becomes dormant in the autumn and winter and regrows in the spring. It’s part of the buckwheat family and thrives in sunny and moist areas. It grows in large clusters of tall canes up to 2.1m high. The stems are flecked with purple, and the leaves are light-green and heart shaped. Japanese knotweed flowers grow in bunches and are creamy-white in colour.
In the winter, all that’s left of the plant are the bamboo-like canes and they can often remain standing for years. In the spring, reddish-purple shoots start to sprout, which will grow into the tall canes throughout the season.
Japanese knotweed is often confused with other plants, due to similarities in appearance. Russian vine also has white flowers but has narrower leaves and the stems do not grow as high. Himalayan honeysuckle also looks similar to Japanese knotweed but has very different flowers when they bloom. Other plants are not as regulated or troublesome as Japanese knotweed, so it’s important to correctly identify your plant so you can deal with it appropriately.
How to remove Japanese knotweed
If you have a large amount of Japanese knotweed in your garden, it may be best to call a professional to help you get rid of it. If you only have a small section to remove, it may be possible to do so yourself. It usually takes around three to four seasons to completely remove Japanese knotweed yourself and a professional will typically take one to two seasons.
A glyphosate-based weedkiller is probably the simplest method to remove Japanese knotweed when doing it yourself. If you are using chemicals in your garden, always read the label and follow the instructions carefully to keep yourself and others safe. Glyphosate weedkiller will attack any green or leafy part of other plants in the area, so make sure to avoid getting it on plants that you don’t want to be affected. The weedkiller isn’t active in the soil though, so you won’t have to worry about it being absorbed through other plants’ roots.
To remove Japanese knotweed with weedkiller, take the following steps, starting in the summer or early autumn:
- Cut down the stems and canes as much as possible
- Spray the cut canes with the glyphosate weedkiller
- Wait at least seven days for the weedkiller to take effect and then pull out all that’s left of the weed, including the root
- Mow over the area weekly, to prevent it from regrowing
- Apply weed killer to the area twice a year, to ensure it doesn’t grow back
It’s illegal to add any amount of Japanese knotweed to your compost or garden-waste bins, as it’s classed as controlled waste. To get rid of your cuttings and roots, you can either safely burn the waste or have it disposed of at a licenced landfill site. If you’re moving the waste off your property, it’s best to get a professional to do so. They’ll have strict rules around cleaning out their vehicle once the waste has been taken to landfill, to prevent any part of the plant that may have been left behind from falling into the wild.
If you are unable to remove Japanese knotweed from your garden this way, you should call a professional. They will be able to offer an insurance-backed guarantee and also report on risk for mortgage purposes. The removal of a Japanese knotweed problem then gives you a great opportunity to get a free valuation and sell your house online via a trusted online estate agent like SOLD.CO.UK