Japanese Knotweed can cause very serious problems for homeowners and their gardens, with some even having mortgages denied because of it. The plant can be a major headache as it can grow up to seven feet tall, cause damage to properties and be extremely difficult to remove.
When left unchecked, the knotweed can grow through cracks in concrete, tarmac in driveways, drains and cavity walls. According to data from Evironet, Nottingham is the 10th worst affected location in Great Britain, having 225 infestations within a four kilometre radius.
The weed spreads rapidly and in the summer the bamboo-like stems emerge from underground to shoot over 2.1 meters whereas in the winter the plant dies back down to ground level. Stem growth is renewed each year from the stout underground.
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What is Japanese Knotweed?
It was originally introduced to Britain as an ornamental garden plant, but is an invasive non-native species and it can suppress all other plant growth. The weed normally affects waysides, garden beds, borders and paving and can have roots 1 metres deep.
The plant grows in large clumps of tall canes with purple spots. Light green heart-shaped leaves come off the stems, followed by hanging clusters of creamy white flowers. The leaves are 14cm in length and the flowers can grow to 15cm.
In late Autumn, the canes die and lose their leaves however the dead plants can often remain standing and sometimes take years to decompose. In Spring, there will be fleshy red shoots growing on their own or on the dead bamboo canes.
How to remove Japanese Knotweed
The removal of Japanese Knotweed takes a lot of determination since it is very hard to remove by hand or by chemicals. It has a reputation of being one of the most troublesome garden weeds.
Small clumps of the weed can be straightforward to manage by digging them out or spraying with weed killer. Gardners' World suggest hiring a qualified professional company to remove large clumps of knotweed.
The professionals will be able to draw up risk reports and offer treatment plans with a guarantee on its complete removal. This is normally an accepted way of removing knotweed by mortgage lenders.
For organic removals of Japanese knotweed, it is important to know that digging out the plant can cause more problems in the long run. The weed is able to regenerate from just the smallest pieces of root.
However, it is possible to gradually weaken the plant by removing all of its leaves as soon as they grow. This will stop the weed from photosynthesising but be aware this method can take many years to have an effect.
If you want to use a chemical approach, a glyphosate-based weed killer is the best option, though it can take several applications, over up to four seasons, to completely eradicate Japanese knotweed. It is best to cut the canes so the weed killer can go through the plant and roots.
Glyphosate-treated knotweed will often regrow the following spring, albeit much less vigorously. It’s important to administer a second application to this growth.
Japanese Knotweed and the law
Please note it is now an offence to cause Japanese knotweed to grow in the wild, either by means of fly-tipping or allowing the plant to escape the confines of your garden.
If you have grown knotweed in your garden and want to sell your property, you will have to remove it before putting it up on the market. Under the Environmental Protection Act 1990, Japanese knotweed is classed as ‘controlled waste’.
This means it is illegal to add it to home-compost or council-run garden waste bins. You are permitted to burn the waste or alternatively, you will have dispose of it at a licensed landfill site.
Japanese Knotweed in Nottinghamshire
The current hotspots for the weed in Nottinghamshire this year are:
- Nottingham - 225 infestations
- Bulwell - 166 infestations
- Ilkeston - 161 infestations
- Mansfield - 154 infestations
- Long Eaton - 131 infestations
