Japanese Knotweed grows quickly and its strong roots can create a destructive underground network undermining buildings and foundations, and potentially causing thousands of pounds of damage.

How quickly does knotweed spread?

Japanese Knotweed can grow up to ten cm per day, with roots growing out in a seven-metre radius, meaning it can quickly spread from one garden to another, infesting whole areas.

The cost of letting Japanese Knotweed spread

Homeowners whose properties become infected with Japanese Knotweed due to negligence by neighbours who let the weed spread will now be able to claim damages. This follows the case of Williams and Waistell v Network Rail. The two neighbours in Maesteg, South Wales, were awarded damages after the rail company failed to prevent the spread of the Japanese Knotweed on to their land.

Stephen Williams and Robin Waistell owned adjoining bungalows backing on to Network Rail property. Japanese Knotweed had been present on the rail company’s land for over fifty years, and the two had first complained about it in 2013.

In 2017, the pair won their case and were each awarded £4,320 to treat the Japanese Knotweed, plus a further sum of £10,000 to compensate them for the fall in property value. Payment was withheld pending an appeal by Network Rail, which was resolved and saw the two men both receiving their money.

The Appeal Court said that the men were entitled to the full payment, although the judgment said that the £10,000 payments were to compensate them the inability to enjoy their property rather than the loss of potential value.

What happens if you let Japanese Knotweed spread?

If you have Japanese Knotweed on your property, you need to get rid of it and prevent it spreading. Allowing Japanese Knotweed to spread from your garden into the wild contravenes the Wildlife and Countryside Act 1981. If you allow the plant to spread to a neighbour’s garden or to private land in general, you may be liable for removal costs, damages, court costs and possible land yourself with an ASBO too.

How do you get rid of Japanese Knotweed?

Excavation is one means of eradicating Japanese Knotweed from your land. It is the fastest means to rid yourself of the weed and a legal requirement if the land is intended for development in the future. However, even the tiniest trace of rhizome left behind in the soil can regrow, for this reason the best solution is to use a professional Japanese Knotweed company, which will provide you with a certificate guaranteeing the weed has been eradicated.

Spray herbicides is the best solution for large infestations in areas that are not ecologically sensitive. The herbicide is applied to the leaves and absorbed down into the rhizome. This treatment normally takes 24 months.

Stem injection is used when you don’t want to affect other nearby plants whilst eliminating Japanese Knotweed. By injecting the herbicide directly into the stem it is absorbed throughout the rhizome deep into the plant’s root system.

How does Japanese Knotweed spread?

Pollination – Although Japanese Knotweed does flower and produce seeds, it is very rare for it to spread in this way.

Stems – New Japanese Knotweed plants can grow from stem fragments. This often happens when machines like strimmers are used in proximity to the weed.

Crown – Even after drying or composting, the crown is able to survive and will rapidly grow new canes when it comes into contact with soil or water again.

Rhizome – Pieces of the underground stem can regrow from as little as a 0.7 gram fragment. Breaking up the rhizome stimulates new growth at an accelerated rate.

Is Japanese knotweed a notifiable plant?

Japanese Knotweed is a garden pest and it is the responsibility of the landowner to manage it. While it is an invasive plant and it is advisable to take action quickly to prevent it spreading, there is no statutory requirement to control/eradicate or even report its presence.

It is, however, an offence, under the Wildlife and Countryside Act 1981, to plant or cause Japanese Knotweed to grow in the wild. This can be enforced by both the police and local authorities, and you may face a fine of £5,000 or even a prison sentence.

Identifying Japanese Knotweed

If you do suspect an infestation of Japanese Knotweed on your or your neighbour’s property, you can send us a photo for a free, no-obligation check. To talk to one of our Environment Officers about Japanese Knotweed or any of our services you can get in touch with Japanese Knotweed Agency on freephone 03335 777 888