Japanese Knotweed through summer and Autumn

Summer Japanese Knotweed Control

Japanese knotweed growth will peak in the latter summer months resulting in dense foliage surrounding thick, hardy stems giving the infestation quite an intimidating presence. Clusters of creamy white flowers appear on the tips of stems in late summer to early autumn and it is at this time the plant is most venerable to herbicide application. Although Japanese knotweed cannot reproduce in the UK via the flowers as a result of only the male plant being present, it is still capable of producing new growth through the underground network of rhizomes spreading as far as seven metres from the original infestation. Herbicide can be applied in a spray to the exterior of the plant, covering leaves in a solution that will be absorbed into to root system and continue the process of inhibiting growth. It is also possible to inject herbicide directly into the Japanese knotweed providing the stems are rigid and large enough to successfully deliver the herbicide using a stem injection unit. The advantage of this is that the Japanese Knotweed Removal chemical is being delivered directly to the target species without risk of contamination of the surroundings, an essential option if the infestation is in close proximity to valuable or protected flora or fauna. The option to excavate the infestation is still available at this time providing that any Japanese knotweed above ground is either disposed of with the contaminated soil or thoroughly dried out and burned.

Autumn Japanese Knotweed Control

Early autumn sees Japanese knotweed in full bloom, covered in clusters of creamy beads of white flowers protruding from stems. As in the latter summer months, herbicide application should be extremely effective, however, this may be offset due to heavy rainfall that is common nationwide at this time of year. Ideally herbicides should be given at least four hours of dry conditions to become rain resistant after application and if the weather seems unlikely to allow this then alternative methods must be found. Some herbicides do contain ingredients that allow for a shorter drying time before becoming unaffected by rain and these can be particularly useful in autumn. During periods of prolonged rainfall, one of the most effective treatments is stem injection, although, the process can be time consuming with each individual stem requiring a dose of herbicide providing that the stem is of the right size and is not damaged. It is important that if a Japanese knotweed infestation is located the surrounding ground is not disturbed as this is the primary method that reproduction is able to occur. If disturbed and displaced, the Japanese knotweed rhizomes (underground creeping stems) are able to produce new plants from pieces as small as a finger nail and this is the main reason that Japanese knotweed thrives on river banks and building sites. This non-native weed is capable of quickly colonising large areas if rhizomes are washed downstream, carried on boots, tyres or vehicle tracks. If, due to bad weather or time restraints, the Japanese knotweed infestation must be excavated, it is of the upmost importance that the work be carried out under the supervision of a trained and experienced specialist, as there is a strong possibility that any movement of contaminated soil will result in the spreading of the infestation throughout the site if proper precautions are not in place. There is a possibility that improper treatment or movement of Japanese knotweed may be in breach of the law which may result in large fines and/or imprisonment.

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