Frequently Asked Questions

Q. Can Japanese Knotweed spread by seed?
A. Although Japanese Knotweed flowers can be alarming, all seeds are infertile and do not cause the plant to spread.

Q. How does Japanese Knotweed Spread?
A. Japanese Knotweed only spreads by rhizomes (the root system), not by seed. As little as 0.2g of rhizome can cause a new infestation to grow.

Q. What does Japanese Knotweed look like?
A. Japanese Knotweed has hollow, bamboo-like stems. The stems zigzag, and off-shoots only protrude from alternating nodes. Stems are green with crimson-coloured speckles in the Spring and Summer months. In the dormant winter months, the stems become very brittle and dark.

Q. When does Japanese Knotweed flower?
A. Japanese Knotweed typically flowers within the months of August-September just before the end of the growing season. The flowers are cream coloured in appearance and form dainty clusters (similar to buddleia/butterfly plant.)

Q. Where does Japanese Knotweed grow?
A. Japanese Knotweed grows wherever the rhizome system can thrive. Typical locations are found within residential gardens, railway lines and industrial sites usually within grass/soil no matter how poor. During our time in the industry, we have also found it in more obscure places such as the middle of ponds, on rooftops and growing out of the tops of walls, just to name a few.

Q. Who introduced Japanese Knotweed to the UK?
A. Japanese Knotweed was first recorded in Great Britain in 1824 and was brought in as an ornamental plant, initially by the Victorians. It was then introduced along railway lines to stabilise the embankments.

Q. Can Japanese Knotweed grow though concrete?
A. Whilst Japanese Knotweed can’t break through clean concrete it will permeate and worsen any cracks that already exist. Japanese Knotweed will break through tarmac and other man-made surfaces, including brickwork and drainage systems.

Q. Why is Japanese Knotweed a problem?
A. Japanese Knotweed has a number of factors which cause issues. Issues can arise whilst buying or remortgaging a property for many, as most mortgage lenders won’t lend without a management plan and company guarantee being implemented, due to the risks of potential structural damage. There is also the legal standpoint, as the plant is on Schedule 9 of the Wildlife and Countryside Act 1981, meaning there are restriction on planting and causing the plant to spread. There is also the ecological standpoint, which is to prevent non-native invasive species from outcompeting our native flora.

Q. What is Japanese Knotweed?
A. Japanese Knotweed is an herbaceous perennial (plant) which originates from Asia.

Q. When does Japanese Knotweed grow?
A. Japanese Knotweed begins to grow early Spring, however small signs maybe noted sooner, weather dependant. The growing seasons tends to begin around April and the plant begins to die back in September/October for the Winter.

Q. What can be mistaken for Japanese Knotweed?
A. To the untrained eye many plants may be mistaken for Japanese Knotweed. The main culprits are typically Bindweed, Common Dock (during the dormant stage of the season), Himalayan Balsam (which is also classed as an invasive weed), Russian Vine, Buddleia, Dogwood and Bamboo.

Q. Is Japanese Knotweed edible?
A. Japanese Knotweed is safe for human consumption and is said to have a tangy lemon flavour. Many recipes can be found online to turn Japanese Knotweed into desserts, soups and even alcohol.

Q. Is Japanese Knotweed poisonous to dogs?
A. Small amounts of Japanese Knotweed is unlikely to cause harm to your pet, either cat or dog.

Q. Can Japanese Knotweed be removed?
A. Japanese Knotweed can certainly be removed. The most cost-effective method of eradication is through herbicidal treatment which spans several years, however instant mechanical solutions are also available, subject to budgets and timescales.

Q. How common is Japanese Knotweed?
A. Although nobody can be certain how much Japanese Knotweed there is in the country, Japanese Knotweed is common in most, if not all areas. In May 2019, the House of Commons Science and Technology Committee published a report of the inquiry on “Japanese knotweed and the built environment” within that It has been estimated that over 2% of development sites and 1.25% of residential properties in Great Britain are affected by the plant, amounting to tens of thousands of sites in total.

Q. Can you buy a house with Japanese Knotweed?
A. Of course, you can both buy and sell a property or land with Japanese Knotweed on site, however, legally this must be declared within the Ta6 form. In most if not all cases, a Japanese Knotweed management plan and company guarantee will need to be implemented for an individual to obtain a mortgage, at the minimum.

Q. Who is responsible for Japanese Knotweed?
A. The responsibility to deal with Japanese Knotweed typically lands on the landowner. In some cases, if Japanese Knotweed can be proven to have been allowed to spread onto neighbouring land, or was not declared on legal forms, a third party maybe liable for the costs, this may lead to legal routes to have the issue resolved.

Q. What is the legal position around Japanese Knotweed?
A. The Wildlife and Countryside Act 1981 provides the primary controls on the release of non-native species into the wild in Great Britain. It is an offence under Section 14(2) of the Act to ‘plant or otherwise cause to grow in the ‘wild’ any plant listed in Schedule 9, Part II’ – This includes Japanese Knotweed. All parts of the plant and any soil contaminated with the rhizome are classified as controlled waste and are required legally to be removed and disposed of by a licensed waste control operator. Antisocial behaviour orders can be issued at companies & individuals to deal with their infestations before the problem spreads onto neighbouring properties. Fines applicable can be up to £20,000 (commercial) and £5,000 (domestic), as well as the cost of the remediation.

Q. Why is Japanese Knotweed hard to get rid of?
A. Japanese knotweed has an extensive underground rhizome system which can be up to several metres deep, making it extremely difficult to dig up and remove completely, to an untrained eye. It only takes a tiny fragment of rhizome to be left behind and the plant will return. Weather conditions, certain locations and terrains, and any disturbances whether human or an act of God can affect the eradication process.