Japanese Knotweed is present on these allotments. CIP have been informed. July 06

Cole Park Allotments may now have caused the solution to this problem. Thanks to Reg, the CIP Rep who had originally informed CIP and we now understand they plan to sort it in August 07 when it is best to treat.

What is Japanese Knotweed?

Japanese Knotweed was introduced to the UK as an ornamental plant during the 1800s. It is commonly found today along railway lines, riverbanks, roads and footpaths, in graveyards, on derelict sites or anywhere that it has been dumped, dropped or deposited.

What does it look like?

Japanese Knotweed forms dense clumps up to three metres in height. It has large, oval green leaves and a stem that is hollow and similar to bamboo. Usually in early spring (although it can be later in the year) the plant produces fleshy red tinged shoots. These can reach a height of 1.5 metres by May and three metres by June.

This plant can grow as much as 2 cms per day and will grow in any type of soil, no matter how poor. Towards the end of August clusters of cream flowers develop and then produce seeds that are sterile. The plant dies back between September and November.

Beneath any stand of Japanese Knotweed will exist an extensive underground root (rhizome) network that can extend several metres around and beneath depending on ground conditions. The spread of the plant is vegetative, ie all new plants are created by fragments of existing plants. A fragment of root as small as 0.8 grams can grow to form a new plant.

Advice for Japanese Knotweed

If you suspect you have Japanese Knotweed you should take care not to allow it to spread. Even the smallest piece of rhizome, stem or crown can potentially form a new plant. Compost Japanese Knotweed separately, preferably on strong plastic sheeting so it is not in contact with the ground. Check the compost regularly to ensure it is not sprouting. Ensure that it is fully decomposed before spreading it on the garden. Do not shred or strim the plant as this could cause rapid spread. Mowing is only advised if you have a collecting box for mowings which can then be composted. Do not dig Japanese Knotweed as this is known to increase stem density and it encourages sprouting and spread.

What to do?

Hand pulling or cutting the plant is a good method of control but will take several years for the rhizome to be exhausted and die. Leave the material on a plastic sheet to dry and then burn it. Do this on site to prevent spread. The cutting and pulling of stems encourages the plant to send up more shoots which can in turn be pulled.

You can also use chemical herbicides, glyphosate is recommended but treatment will need to be ongoing and may take several years depending on how established the colony is.

Avoid digging within 7 meters of a colony of Japanese Knotweed, and avoid moving the soil around the garden as the soil could contain rhizome.

Do not take Japanese Knotweed material to your local recycling centre, Japanese Knotweed has to be treated as ‘controlled waste’. Do not remove Japanese Knotweed material from the site unless you have made a prior arrangement with a licensed landfill site for deep burial. Treatment on site is the preferred option.

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