Japanese Knotweed Identification | What is Japanese Knotweed?

Frequently Asked Questions

Japanese Knotweed is a highly invasive plant that spreads rapidly and can cause damage to property which can impact its value. It is an offence to allow or cause this plant to grow in the wild. You could also become liable for damages if allowed to spread onto neighbouring property.

Starting from small red shoots similar to asparagus in the spring and growing up to 3m tall in the summer with hollow canes and vibrant green heart/shield shaped leaves. This plant produces white flower clusters in autum before dying back for winter leaving a bare brassy footprint of dead hollow canes.

If you suspect you have Japanese Knotweed, do not attempt to deal with it alone, but call in the professionals and book a survey.

There are many plant species in the UK that are harmful to humans and animals, although not being poisonous, Japanese Knotweed can cause house and building damage.

While not harmful to humans, its potential for damage comes from its invasive roots and fast growth rate. In ideal circumstances, Japanese Knotweed can grow up to 10cm a day, and as it spreads it can damage hard surfaces, like concrete, tarmac and brick walls.

There are a number of options for controlling Japanese Knotweed from herbicide treatments, excavations with relocation to burial options and off-site disposal. These methods can also be combined for increased success of lasting control.

Japanese Knotweed can grow up to 10cm per day, and because of this rapacious growth, it has been known to cause damage to building structures and substructures by targeting weak points, such as cracks in masonry, and attempting to grow through them. Typical damage from knotweed includes damage to tarmac and paving.

Lenders are cautious with properties that are affected by Japanese Knotweed, but its not impossible to get a mortgage or re-mortgage. It is a legal responsibility to declare the presence of Japanese Knotweed in your home report. A lender may refuse a mortgage application if Japanese Knotweed is not professionally managed with sufficient guarantees. Find out more about buying or selling a house with Japanese Knotweed.

Japanese Knotweed can manipulate weaknesses and cracks in concrete and other building and drainage structures. If ignored, Japanese knotweed can undermine the integrity of these structures causing structural risk and potential damage.

Japanese Knotweed spreads from fragments of roots moving from one location to another.

The lack of natural opposition has resulted in rapid colonisation and spread of Japanese Knotweed across the country.

There are a few distinctive features to lookout for in winter:

  • Dark brown and bare stems
  • Dead flowers will remain for some time, forming spider-like curled, dead growth
  • The alternate stem arrangement will remain evident until it falls off and decomposes
  • Later in winter, the dead, hollow bamboo-like canes may be seen in the ground and still connected to the crown and root system.
  • Early shoots may appear, like small red arrows, towards the end of winter

Find out more about winter identification of Japanese Knotweed.

Japanese Knotweed shoots are stems that are red/purple in colour, hollow and bamboo-like, with leaves that are a lush green.

In short – no, but read our article on Dogs and Japanese Knotweed for more information.

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Is Japanese Knotweed Dangerous? Japanese Knotweed Shoots | JBB Knotweed Solutions

Is Japanese Knotweed Dangerous?

If you’re unfortunate enough to have discovered some Japanese Knotweed in your garden, you’ll most certainly be asking this question.