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11 Reliable Ways To Identify Japanese Knotweed

Japanese knotweed warning sign

What is Japanese Knotweed?

Japanese Knotweed is a highly invasive plant, it has the ability to grow through things such as concrete, tarmac and bricks, causing damage and havoc if you have this on or near your property. I hear you ask why don’t you just cut it down? Unfortunately getting rid is a little more complex, it cannot just be cut down due to its vast root system (rhizomes) it will just grow back quickly and more densely making your infestation worse.

The Wildlife and Countryside Act 1981 section 114 (2) (WCA 1981) classifies Japanese Knotweed as a controlled plant, so care must be taken when exterminating or moving the plant material. It is not illegal for you to have the plant on your property however it is illegal to cause or allow the plant to spread in the wild, this can land you a £2,500 fine or 2 years in prison.

Japanese knotweed growing through stone

How to Identify Knotweed:

Identification is important due to the problems that it can cause to you as a homeowner, especially if you are considering selling. Identification can be difficult because throughout the growing season and it’s growth cycle the pesky plant goes through different stages, meaning the characteristics of Japanese Knotweed you need to be looking out for changes. Be aware that there are other plants that look similar, like Russian Vine and Giant Knotweed. However, there are some tell tale signs that should signify whether you have an infestation or not.

11 Most Common Characteristics of Knotweed

  1. Bright luscious green coloured leaves
  2. Shoots grow in a zig-zag pattern
  3. Shovel or a heart with a flat bottom shaped leaves
  4. Red and purple speckles on the stems
  5. Creamy white flowers
  6. It grows to around 3m (nearly 10ft!) in height
  7. Hollow bamboo like stems
  8. Japanese Knotweed roots (rhizomes) are brown on the outer and yellow / orange on the inside
  9. Visible nodes between the stems, similar to bamboo.
  10. Rhizome crown that has densely clumped together stems.
  11. Japanese Knotweed Shoots look similar to asparagus.

Japanese Knotweed in Spring

Japanese Knotweed shoot in the spring time

In the spring and the start of the growing season Japanese Knotweed shoots will start to appear from the ground. It looks similar to asparagus with a red/purple colour. The leaves form in a red or dark green colour and are rolled up. By the end of spring these stems can reach up to 3 meters tall.

Japanese Knotweed in Summer

Japanese knotweed in summer with white cream flowers

In the summertime the leaves form their shovel shape and change colour from red to a luscious green, these leaves can grow up to 20cm in width. Towards the end of summer clusters of Japanese Knotweed flowers appear off the zig-zag stems, creamy white in colour. The main stems are hollow and bamboo like with a similar look to rhubarb.

Japanese Knotweed in Autumn & Winter

Dead and dying japanese knotweed

In autumn the bright green leaves will start to yellow and wilt, the plants remain at the same height around 2-3 meters, the colouring of the stems/canes begin to turn brown.

Japanese Knotweed in winter – All the leaves die off along with the canes and the plant remains dormant until spring. The hollow dark brown canes become brittle and they begin to collapse on top of each other and die all the way back to the rhizome. However if there is a large infestation/growth then some of the stems may remain, particularly cold winters will kill them off more however.

If you’re still having problems identifying Japanese Knotweed, this video may offer you some help.

Problems It Can Cause

Japanese Knotweed shoots can grow through materials such as concrete or tarmac, causing damage to structures and foundations. It has also been known to penetrate drainage systems and break these also. These can obviously be expensive problems to have put right.

It can knock tens of thousands of pounds off a house’s value, if you’re buying a property it is not uncommon for mortgage brokers to refuse mortgages on properties that have Japanese Knotweed on their land or even nearby on neighbouring properties. Similarly most building insurance won’t cover damage by this plant. This is due to the damage it can cause structurally if the plant is near a building, there are many cases of Japanese knotweed damaging building foundations, growing under and into homes as well as it damaging drainage pipes. This is due to the part of the plant that is not visible the rhizomes, basically a huge expansive root system.

The Royal Institution of Chartered Surveyors (RICS) have released a paper that breaks down the levels of severity of Japanese Knotweed Infestation, as well as suggested methods of removal. The document also suggests that contractors that are carrying out Japanese Knotweed removal treatment should provide a detailed plan with an insurance backed guarantee.

Estate Agents are also legally required to let prospective buyers aware of Japanese Knotweed if it is present on the property, however it is quite common that this gets missed out and buyers aren’t made aware of it.

How Housing Triage Can Help you

At Housing Triage we work with surveyors to identify knotweed and how much Japanese Knotweed you have. Once your claim has been approved we work with solicitors to help you receive the maximum compensation you can get to help fund the removal of this vicious plant.

Contact us if you think you’ve seen this plant on or near your property, you may be eligible to claim!

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