Japanese Knotweed Facts
The problem
The plant can cause significant damage to construction work and has the power to grow through tarmac, paving stones, brickwork and cement. Purely through cell expansion, the plant will find the smallest crack or joint and then force its way through, cracking the already damaged masonry.
On river courses and steep slopes, the plant will damage and weaken the banks with its extensive root and rhizome structures weakening the soil structure. The debris from the plant dying off in winter falls or is washed into streams and rivers and creates blockages and increases the risk of flood.
The plant's leaf canopy of broad leaves obstructs light to the ground preventing natural flora and fauna from growing. Dead vegetation decomposes slowly over a number of years and also obstructs light. It also creates a fire risk during the summer months and during dry periods. The plant can survive extreme heat and is found in volcanic areas within its natural habitat.
Factfile
- Japanese Knotweed shoots are capable of growing through tarmac and concrete
- A piece of rhizome less than 0.7g which is smaller than a fingernail is capable of growing into a new plant and starting a new infestation
- The plant is so resilient it is even immune to burning and can rise from the ashes to grow once again
- Japanese Knotweed grows on average 40mm per day
- It is estimated that the plant covers a site every 10km2 in the UK
- The biggest cause of the Japanese Knotweed spread is fly-tipping
- Japanese Knotweed has been known to spread after travelling from machinery used on building sites
- The plant stores nutrients in a maze of roots underground thus enabling it to hibernate in the winter months
- Dead JK stalks and stems can take up to 2 years to fully decompose
