Corvus Wildlife Management

Invasive Weed Management & Eradication

Invasive and injurious weeds can give rise to a range of development liabilities and legal obligations. Weed control and/or eradication is increasingly a condition of planning permissions.

These pages highlight problems associates with Japanese Knotweed, however a range of other weed control services (e.g. Giant Hogweed, Ragwort, Himalayan Balsam, Rhododendron etc.) are also provided by Corvus. For information on these species contact us directly.

Japanese Knotweed (Fallopia japonica) a rhizomatous perennial, was introduced to the UK as an ornamental plant in the 1850's and quickly established itself throughout the British Isles.

The plant does not produce seeds, but regenerates from a rhizome (root). As little as 0.6g of the rhizome is sufficient to enable the plant to grow in any given area. This astonishing regenerational ability results in soil containing the rhizome being classified as controlled waste, increasing the costs of removal & landfilling from any given site.

The plant causes harm by its ability to exploit flaws in engineered structures. Hard surfaces such as foundations, brick, concrete & tarmac can all be penetrated with relative ease by the plant, causing a loss of cohesion and ultimately, structural failure. The cost of removing Japanese Knotweed from any given development site can be significant. However the liabilities accruing from ignoring the problem are certain to prove much more costly in the long term.

Stands of Knotweed on development sites can cause significant problems at concept planning, construction and operational stages. The plant is found throughout the UK & Ireland.

Time frames for chemical removal (3+ years) can be incompatible with other site requirements and physical removal or on site containment & treatment may be required in some instances. Corvus have significant experience of the delivery of Knotweed Management Plans compliant with the Environment Agency's Knotweed Code of Practice and all relevant staff hold NPTC (City & Guilds) Certification in the safe use of pesticides (PA2, PA6 & PA06A). Staff also undertake CPD compliant wit the Requirements of the National Register of Sprayer Operators (NRoSO).

Information on relevant Legislation can be found at our Legislation page.

If you are a development professional you should be able to identify Japanese Knotweed on sight. See our Japanese Knotweed identification guide.

Information on treatment and eradication techniques practised by Corvus can be found at our Treatment & Eradication Page.

Other Knotweed Species

In addition to the common Japanese knotweed (Fallopia japonica) there is a smaller compact variety Fallopia japonica var. compacta, reaching a height of 1 metre and a Giant knotweed (Fallopia sachalinensis), growing up to 5 metres. A hybrid between Japanese knotweed and Giant knotweed, Fallopia x bohemica is also found in the UK.

There are slight differences in leaf shape and size that distinguish between the species but generally leaves are shovel shaped. The base of the leaf, joining the stalk, is straight on a Japanese knotweed leaf whereas on a Giant knotweed leaf it is lobed, forming a heart shape. The hybrid is in-between with a slightly lobed base. Other introduced members of the Polygonaceae family are often mistaken for Japanese knotweed. The most common being Himalayan knotweed (Persicaria wallichii) with elongated leaves.

In terms of In terms of best practice, there are no differences in the management of all the above species. All species must be treated in the same way.

See below for a guide to knotweed varieties, and to the right for a Japanese Knotweed Identification Guide.