A guide to removing Japanese Knotweed, including the costs and what the job entails.
Japanese Knotweed is renowned as a problematic and tenacious plant, and removing it can be a complicated and time-consuming process, as well as an expensive one. If left untreated, it will spread very quickly and can even cause significant damage to building foundations as it grows. This article will detail the best method of removing Japanese knotweed from your property and ensuring that it doesn't return.
Japanese knotweed (Fallopia japonica) is a plant that spreads rapidly as it grows. In spring, reddish-purple fleshy sprouts appear from crimson-pink buds at ground level. Its leaves are heart or shovel-shaped and up to 14cm (5½in) in length and have a zig-zag design along the stems. The stems die back down to ground level in winter, but the dry canes remain for many months or longer. The creamy-white flower tassels produced in late summer and early autumn reach up to 15cm (6in).
In winter months the plant dies back to ground level, but by early summer the bamboo-like stems emerge from rhizomes (root-like features) deep underground to shoot to over 2.1m (7ft) tall. The weed progresses, it strangles suppressing all other plant growth. Eradication requires determination as it is tough to remove by hand or eradicate with chemicals. There is now updated legislation which covers the control – including the disposal – of invasive plants such as Japanese Knotweed, and these legal issues must be adhered to!
Removing Japanese Knotweed can be a costly service, as it's incredibly persistent and may take a few tries and treatments to eradicate it from an area thoroughly.
Here are the average prices to remove Japanese Knotweed from a domestic property:
| Size of area | Cost |
|---|---|
| Small (20 square metres and below) | £450-£2,000 |
| Medium (20-50 square metres) | £2,000-£3,000 |
| Large (50-100 square metres) | £3,000-£5,000 |
Here is a breakdown of the costs for treatments used on commercial sites suffering from infestations:
| Treatment | Small | Medium | Large |
|---|---|---|---|
| Herbicide (over five years) | £400-£2,000 | £2,000-£3,100 | £3,100-£5,000 |
| Dig and root barriers + herbicide | £500-£3,100 | £3,900-£7,000 | £9,900-£30,000 |
| Pick & sort | £500-£4,100 | £3,100-£7,000 | £9,900-£30,000 |
| Onsite relocation + herbicide | £3,100-£8,000 | £4,100-£10,000 | £10,100-£20,000 |
| Onsite burial | £4,100-£12,000 | £7,100-£18,000 | £16,000-£30,000 |
| Excavation & disposal | £3,100-£12,000 | £6,100-£30,000 | £30,100-£70,000 |
It is also an option to just maintain the Japanese Knotweed at a much lower cost. You can pay for safety equipment, chemicals and collection annually and reduce the costs to between £100-£250. This however doesn’t solve the issue and just prevents it from causing any damage.
Japanese Knotweed has to be wholly eradicated to ensure that it isn't able to return. To do this, there are four approaches you can use to get rid of this plant, and this invasive weed sometimes requires multiple attacks to control it. Methods required are usually:
Only by using these methods can you be reasonably assured that you have entirely removed the ability of the knotweed to reproduce and gain a foothold again. This task is going to entail the use of pesticides, lots of pruning, and a severe amount of root digging. You will need:
Japanese Knotweed can have roots that reach a couple of metres into the ground, and it all needs to be removed to prevent the knotweed from returning later. To be able to remove that depth of soil, you may have to employ a mechanical digger and sift through the soil once it has been removed to extract any root material before returning the sorted dirt.
It cannot be stressed enough about how necessary the removal of Japanese Knotweed plant is to ensure that it doesn't return later. Once it has been removed, you have the problem of safe disposal and this is covered by many legal complications.
The Government guidance website states that you must get rid of Japanese knotweed waste off-site by moving it to a disposal facility that's permitted, such as a landfill site that has the right environmental permit to handle the material. Legally, you must prevent Japanese knotweed on your land from spreading into the wild and causing a nuisance. You may be fined up to £5,000 or be sent to prison for up to 2 years if you allow contaminated soil or plant material from any waste you transfer to spread into the wild.
This means that it is not acceptable to simply cut back knotweed or dig it up and take it to your local waste and recycling centre. If it does not have the right environmental permit, you could be fined or sent to prison. The Government website continues to state that you must not dispose of Japanese knotweed with other surplus soil or sell soil contaminated with Japanese knotweed as topsoil. You can only reuse knotweed-contaminated soils after treatment, on the site where they were produced.
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Here is a list of commonly asked questions regarding removing Japanese Knotweed.
Japanese Knotweed is a striking plant, in spite its damaging potential. The way it looks changes depending on the season. The main things to look out for are:
This is usually dependent upon the lender involved, and many will reject a mortgage application outright if a survey report indicates that there is Japanese Knotweed on the property. Some mortgage lenders will count on the surveyor's report to decide whether it presents a considerable danger to the property and the likelihood of selling it in the future.
However, it's important to remember most lenders will demand a professional removal, including a guarantee against the plant's return, before offering a mortgage proposal. The lender may also need the buyer to provide written confirmation that they are happy to proceed with the purchase of the house following an infestation of Japanese Knotweed.
Yes, but it is essential to go along with these steps:
No, it's not poisonous to the touch. Although it is very destructive as a plant, the only hazard of dealing with and touching the plant, is that you could trigger it to spread further just by pulling it out.
There are a few varieties of Japanese knotweed, including Giant knotweed, which has larger leaves and are taller plants. It's not as aggressive as Japanese knotweed but has the same legal status and treatment processes. There is also a variant known as Bohemian knotweed, which is a hybrid of Japanese and Giant knotweed and a recognised Japanese knotweed variation through a smaller, less widespread variety of the main plant.
