Japanese Knotweed Treatment & Removal | Northern Tree Services

What Is Japanese Knotweed?

Reynoutria japonica, synonyms Fallopia japonica and Polygonum cuspidatum, is a large species of herbaceous perennial plant of the knotweed and buckwheat family Polygonaceae. It is commonly known as Asian knotweed or Japanese knotweed. It is native to East Asia in Japan, China and Korea. In North America and Europe, the species has successfully established itself in numerous habitats, and is classified as a pest and invasive species in several countries.

Japanese knotweed has hollow stems with distinct raised nodes that give it the appearance of bamboo, though it is not related. While stems may reach a maximum height of 3–4 m (10–13 ft) each growing season, it is typical to see much smaller plants in places where they sprout through cracks in the pavement or are repeatedly cut down. The leaves are broad oval with a truncated base, 7–14 cm (3–5 1⁄2 in) long and 5–12 cm (2–4 1⁄2 in) broad,[7] with an entire margin. The flowers are small, cream or white, produced in erect racemes 6–15 cm (2 1⁄2–6 in) long in late summer and early autumn.

Why is it bad?

Japanese Knotweed is an invasive plant that is slowly but surely invading Ireland. Japanese Knotweed is one of Ireland’s most unwanted species and it poses both huge environmental and economic threats.

The principle means of spread of Japanese Knotweed is via fragmentation of stems and rhizomes and the plants very strong resilient underground rhizome growth.

Japanese Knotweed thrives on disturbance, the tiniest piece can regrow, in the past fly tipping and transportation of soil containing rhizome fragments have been a major cause of spread in both the urban and rural environments.

Japanese Knotweed is now very common and widely distributed across a variety of habitat types in Ireland – It is most prominent on roadsides, hedgerows, railways, waste ground, river banks and wetland habitats due to its vigorous growth rate.

It quickly forms tall stands shading out the areas below it, threatening the survival of native plant species and in turn insects and other animal species. The loss of biodiversity from the impacts of this invasive plant is a major concern to us all.

Japanese Knotweed on finding any weak spot can grow through all kinds of hard surfaces, including brick, tarmac and concrete and in some cases has been known to undermine the very foundations of a property.

What can I do?

It is important to always to seek professional advice or professional services before tackling Japanese Knotweed

When dealing with Japanese Knotweed it is more of a case of what not to do…

Do not strim, cut, flail or chip the plants as tiny fragment can regenerate new plants and make the infestation harder to control
Do not attempt to dig out Japanese Knotweed, this can actually encourage the plant into growing faster, therefore colonising an area more aggressively
Do not move or dump soil which may contain plant material as this may also add to its spread.
Do not attempt to pull the plant out of the ground, as this can expose part of the infectious crowns, stimulating growth
Do not use unlicensed herbicides close to any watercourses, plants or wildlife
Do not compost any part of the plant as due to the resilient nature of knotweed it could survive and grow on when the compost is ready for use
Do not dispose of Japanese Knotweed in garden waste allotments as this just transport the plant to new locations
Do not spread any soil that has been contaminated with Japanese Knotweed rhizome as new plants will sprout