Japanese Knotweed

Fallopia japonica

Japanese knotweed

Japanese knotweed (Fallopia japonica) is a weed that spreads rapidly. In winter the plant dies back to ground level but by early summer the bamboo-like stems emerge from rhizomes deep underground to shoot to over 2.1m (7ft), suppressing all other plant growth. Eradication requires determination as it is very hard to remove by hand or eradicate with chemicals. New legislation now covers its control – see below.

Leaves

Leaves are heart or shovel-shaped and up to 14cm (5½in) in length and borne alternately (in a zig zag pattern) along the stems.

 

Japanese knotweed leaves

Flowers

The creamy-white flower tassels produced in late summer and early autumn reach up to 15cm (6in).

Japanese knotweed flowers

Preferred Habitat

This plant occurs in a wide variety of habitats, in many soil types, and a range of moisture conditions. It appears to be found primarily in disturbed open areas with plenty of sun; shade depresses its growth. Edges of roadways and streambanks are common locations at which to find Japanese Knotweed.

Weed Control

When tackling Japanese knotweed, cultural control methods pose some problems.

  • Digging out this deeply penetrating plant without professional help, even if feasible, creates problems over disposal as Japanese knotweed is classed as ‘controlled waste’ under the Environmental Protection Act 1990. This requires disposal at licensed landfill sites
  • Specialist Japanese knotweed contractors must be registered waste carriers to safely remove the weed from site but check first before employing their services
  • Alternatively, it can be destroyed on site by allowing it to dry before burning

On no account should Japanese knotweed be included with normal household waste or put out in green waste collection schemes.

If using chemical control, it usually takes at least three to four seasons to eradicate Japanese knotweed using weedkiller. Professional contractors, however, will have access to more powerful weedkiller that may reduce this period by half.

When using weedkiller, always follow the instructions on the pack to make effective and economic use of the product while minimising risks to people and the environment. For home gardeners, perhaps the most effective and simplest method to tackle Japanese knotweed is with a glyphosate-based weedkiller.

Not Just a Weed

Some of the most important health benefits of Japanese knotweed include its ability to prevent and treat cognitive disorders, improve heart health, lower your risk of cancer, reduce gastrointestinal distress, lower blood pressure, maintain proper insulin levels, and many other unique benefits.

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At Vialii, we are strong proponents of organic gardening and try to avoid weedkiller if we can. To many people, weeds are wonderful things, whether they are grown as pretty wildflowers or for their health benefits. But we understand they can be frustrating in gardens so our Weedipedia pages detail our most common weeds, how to identify & get rid of them but also their benefits too. If you need help getting rid of your own weeds please get in touch. 


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