Japanese knotweed Identification
Japanese knotweed is a tall, vigorous ornamental plant that escaped from cultivation in the late nineteenth century to become an aggressive invader in the urban and rural environment.
Japanese knotweed, scientific names Fallopia japonica (Houtt. RonseDecraene), Reynoutria japonica (Houtt.) or Polygonum cuspidatum (Siebold &Zuccarini) is a member of the dock family (Polygonaceae). It is a rhizomatous (produces underground stems) perennial plant with distinctive, branching, hollow, bamboo-like stems, covered in purple speckles, often reaching 2-3 m high. The leaves of the mature plant are up to 120 mm in length with a flattened base and pointed tip and are arranged on arching stems in a zig-zag pattern.
The plant flowers late in the season, August to October, with small creamy-white flowers hanging in clusters from the leaf axils (point at which the leaf joins with the stem). The underground rhizomes are thick and woody with a knotty appearance and when broken reveal a bright orange-coloured centre. The rhizome system may extend to, and beyond, a depth of at least 2m and extend 7m laterally from a parent plant. During winter, the leaves die back to reveal orange/brown coloured woody stems which may stay erect for several years. Stem and leaf material decomposes slowly, leaving a deep layer of plant litter. During March to April, the plant sends up new shoots, red/purple in colour with rolled back leaves. These shoots grow rapidly due to stored nutrients in the extensive rhizome system. Growth rates of up to 40 mm a dayhave been recorded.
Only female Japanese knotweed (F. japonica var japonica) plants have been recorded to date in the UK.
Two species closely related to Japanese knotweed are also found in the UK. These are, Giant knotweed (Fallopiasachalinensis), a much taller plant which reaches a height of 5m; and a smaller compact variety (Fallopia japonica var. compacta), which grows to a height of only 1m.
The hybrid (Fallopia x bohemica) (a cross between Japanese knotweed and Giant knotweed) is also found throughout the UK but is not as common as the Japanese. Both Giant knotweed and the hybrid react to the same methods as used for Japanese knotweed Control.
It is worth noting that from a legal perspective, it is not an offense to have Japanese knotweed on your land and it is not a notifiable weed. Allowing Japanese knotweed to grow onto other people’s property may be regarded as a private nuisance under common law and this would be a civil matter.
Although there are a number of non invasive options available, it should be noted that they take a number of years in order to be effective. There are several herbicides that are cleared for use by Japanese Knotweed Specialists, the choice of chemical will depend on the type of area, surrounding plants and proximity to water courses.
Perfect Ground Solutions are Japanese Knotweed specialists and part of our services will involve a detailed look at your particular problem and a report on the best way forward to make sure that you receive the most suitable and cost effective solution to your problem.
Japanese Knotweed Treatment using herbicides is a tried and tested method of removing this plant. It is not instant and needs to be carried out by Japanese Knotweed Contractors who have an understanding about how the plant grows and how and when to apply which herbicides.
The method of application is also important. Stem injection is an ideal method of application as it concentrates the chemical where it is needed and removes the risk of over spraying neighbouring plants.
Most successful results from the use of herbicides occur from treatment in late summer and early autumn as the Knotweed is drawing nutrients, and hence the herbicide, down into its root structure before it dies back for the winter. It is imperative that during the treatment program, the Knotweed and its surrounding area should remain undisturbed. This is not only to ensure that each application of herbicide is as thorough as possible but also to prevent the Knotweed from spreading.
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