Japanese Knotweed is dominating gardens this summer

Japanese Knotweed is dominating gardens this summer
Japanese Knotweed is dominating gardens this summer

Japanese Knotweed can wreak havoc on a building’s infrastructure, growing into basements and causing structural damage to buildings, which can devalue properties and lead to the refusal of mortgages.

The invasive plant can grow more than 1m in height in three weeks with the complex root system going down 3m and out 7m, spreading so far underground that it finds its way into pathways, walls and existing cracks in concrete.

Spring frosts followed by dry weather may cause Japanese Knotweed to “come back even stronger” and dominate other species of plants. The Property Care Association (PCA) expects a surge of weeds every early June, but in 2021 it may have been more sudden and concentrated than usual.

PCA’s Invasive Weed Control Group technical manager, Dr Peter Fitzsimons, explained how 2021 had the coldest Spring for eight years, and all plants were delayed by the cooler air and soil. As the nights grew shorter, and the weather began to warm up, with moisture still in the soil from Spring rains, Japanese Knotweed is now thriving and growing rapidly.

Removing the invasive plant can be very difficult, and often requires homeowners to hire professionals to treat it. However, it is illegal to remove Japanese knotweed waste from a site yourself.

We recommend treating Japanese Knotweed as soon as it is identified. Clearway’s teams are qualified and accredited to use undiluted, industrial-strength Glyphosate. For larger plants, this is injected directly into each stem, and for smaller plants, it is sprayed onto the foliage. This industrial-strength herbicide treatment is the only effective eradication method, but this can take 2-3 years of chemical treatments, even when applied 2-3 times per year as recommended.

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