How to Handle The Japanese Knotweed

Identify Japanese Knotweed And Get Rid Of It

Last Updated on May 20, 2022 by Real Men Sow

Japanese knotweed (Fallopia japonica), is a weed that spreads quickly. The plant will die back to the ground in winter, but the bamboo-like stems that emerge from the rhizomes underground can shoot up to 2.1m (7ft) by the beginning of summer which suppresses all other plant growth. It is difficult to eradicate by hand or with chemicals, therefore, you’ll need determination for eradication.

Japanese KnotweedWhat is Japanese Knotweed?

Japanese knotweed is a strong, clump-forming perennial that grows quickly and has dense, tall stems. The stout, deeply penetrating stems are renewed each year.

Rhizomes are creeping, swollen, root-like structures which look like stems. Along its length, roots, stems with flowers and stems with leaves are formed. You can see plants like Anemone Nemorosa and border iris.

Knotweed Colour

You’ll see them as reddish-purple fleshy shoots emerging from ground level in Spring. They grow quickly and produce dense stands of bamboo-like canes that reach heights of 2.1m (7ft). These canes are characterized by purple flecks and grow branches along their length.

Identify Japanese Knotweed In Winter

The leaves are either heart-shaped or shovel-shaped, up to 14cm (5 1/2 inches) long and borne alternately (in a zigzag pattern), along the stems. Winter brings the stems to their lowest point, but dry canes are left for several months or more. The cream-white flower tassels that are produced in the late summer and early fall reach as high as 15cm (6in)

It is crucial to identify the Japanese knotweed because there’s a possibility to confuse Japanese knotweed with other plants, such as:

  • Fallopia baldschuanica (Russian vine)
  • Leycesteria formosa  (Himalayan honeysuckle)
  • Houttuynia cordata
  • Persicaria microcephala (e.g. P. microcephala ‘Red Dragon’)

The Problem With Japanese Knotweed

Even though it is not a common species in the United States, Japanese knotweed can grow from small sections of rhizomes. It is an offense to allow Japanese knotweed to grow wild, according to Schedule 9 of 1981 Wildlife and Countryside Act.

The Legal Situation

Buying and Selling Property

The seller must declare whether Japanese knotweed (Fallopia japonica), is present on the property. This is done through a TA6 Form – which is the property information used for conveyancing. Although your solicitor or conveyancer can provide you with full legal advice, the following summary is available:

  • It is your responsibility, if you sell, to inspect the garden for Japanese Knotweed. You will need to fill out the TA6 form to confirm that your property has Japanese knotweed growing in it. If it is, you must also provide a plan to eradicate it from a professional company.
  • Japanese knotweed is a potential problem in your purchase, and it should be in your TA6 forms. It’s possible that the assurance of eradication of the Japanese knotweed by your mortgage lender will happen before they approve the funds. A management plan prepared by a professional eradication firm, backed up by a transferable warranty, is often sufficient. This plan should be provided by the seller prior to the purchase.
  • It is important to be proactive and inspect the property for Japanese knotweed, regardless of whether you are a seller or a buyer. This will help you avoid disputes over the identity or failure to disclose the presence of a plant or the absence of a management program. These can lead to delays and increased costs in the purchase process.

Get more information through The Royal Institute of Chartered Surveyors’ website.

New Legislation

Amendment to the Anti-social Behavior, Crime and Policing Act 2014 contains invasive non-native plants, including Japanese knotweed. These are key points to help homeowners understand how this impacts them:

  • Although it is legal to grow Japanese knotweed in your yard, you should make an effort to eradicate this non-native invasive plant from your property. It could have a “detrimental impact of a persistent and continuing nature on quality of life for those in the area” and property owners could be charged.
  • It’s best that you contact your neighbors if there are Japanese knotweed problems in their gardens. They may be already taking steps to eliminate this difficult weed. Before you contact your council about the legislation, it’s best to take these informal steps first.
  • For a small, isolated clump, homeowners can try to control it themselves. A specialist company can manage the control and eradication of plant wastes at licensed landfill sites.

How To Get Rid Of Japanese Knotweed

Control

A specific cultivar number and are usually bred to improve certain characteristics such as flower size, colour, flavour, fragrance, hardiness, resistance to disease, etc. It is also worth noting that variety can also refer to a plant with slight differences in appearance. Malva alcea var. Fastigiata is different from other plants because it has an upright habit.

The first line of defense should be cultivar selection, garden hygiene, and encouraging or introducing natural enemies. Use chemical controls only on highly targeted and limited ways. It’s best to avoid pests, diseases, and weeds that pose a threat to the environment or habitats of important heritage specimens or native wildlife.

Cultural Control

Cultural control methods can pose problems when dealing with Japanese knotweed.

  • This deeply penetrating, invasive plant is difficult to remove without professional assistance, even if it is possible. There’s also a requirement to dispose of material at licensed landfill sites
  • To safely remove Japanese knotweed, specialist Japanese knotweed contractors must have a registered waste carrier. However, you should screen them before hiring their services.
  • You can also dispose of it on-site by drying it before burning it.

You should not mix the Japanese knotweed with household waste or placed in green waste collection systems.

Weedkiller Control

Eradication of the Japanese knotweed through weed killers takes in about three to four years. However, professional contractors will have access to stronger weed killers, which may reduce the time by half.

To make the most of weedkiller, be sure to follow all instructions. This will ensure that you are using the product efficiently and economically while minimizing the risks to the environment.

  • Roundup Tree Stump Weedkiller is a glyphosate-based weedkiller that can help control Japanese knotweed. This is the best and easiest way for home gardeners. The label will contain a recommendation on how to control Japanese knotweed. You can use it to cut canes, or as a foliar spray. Roundup Ultra and SBM Job done Tough Weedkiller (soluble only) also have this label control.
  • You can also try other stronger formulations of Glyphosate 
  • Glyphosate-treated knotweed can often produce bushy, small-leaved regrowth of 50-60cm (20in-3ft), the next spring. This regrowth will look very different from the normal plant, so it is important to treat it.
  • Keep in mind that you can always ask a professional company for Japanese knotweed control. The home gardener cannot get an insurance-backed guarantee without it. This is important if you are planning on selling your property soon or if your neighbor threatens litigation due to the spread of Japanese knotweed.

Glyphosate is not selective and that’s why you should avoid putting them around all green parts of garden plants. You can use the chemical around the base of non-suckering woody plant bases provided that the bark is mature, woody, and brown. Glyphosate does not penetrate the soil, so garden plants won’t absorb them through their roots.

Seeking Help From The Professionals

Professional Companies can do the Japanese Knotweed removal for you. They can provide advice on how to remove Japanese knotweed and give insurance-backed guarantees if necessary.

  • The Royal Institution of Chartered Surveyors has partnered with the Property Care Association to create the PCA Invasive Weed Control Group, trade body for Japanese knotweed experts. This registry includes vetted contractors and consultants.
  • The Invasive Non-native Specialists Association maintains a membership database of consultants and contractors by calling 0800 1300 485.
  • The British Association of Landscape Industries (BALI), has a list of members that offer invasive weevil control.
  • Trustmark Government Endorsed Standard has a ‘Find a Tradesman’ scheme, which includes Controlling invasive weeds .

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