Japanese Knotweed (named as Fallopia japonica, Polygonum cuspidatum, Reynoutria japonica) is a large invasive weed of perennial plants. These invasive species was originated in Japan, China and Korea and has successfully spread across Europe, North America and various other countries. It is listed as one of the world’s 100 worst invasive species by World Conversation union. In the UK it is listed under Section 14(2) of the Wildlife and Countryside Act 1981, which states that “if any person plants or otherwise causes to grow in the wild any plant which is included in Part II of Schedule 9, he shall be guilty of an offence.”
These invasive weeds have small green-white flowers, blooms between late summers to early bottoms. Its stems are green with red purple specks and can grow 2-3 meters height grows in large density. While its leaves are 7–14 cm long and 5–12 cm broad with a flattened base and pointed tip and are arranged on arching stems in a zig-zag pattern. Japanese Knotweed is been called by various names which includes Himalayan fleece vine, monkeyweed, donkey rhubarb, Huzhang, Hancock’s curse, pea shooters, sally rhubarb, Japanese bamboo, elephant ears, American bamboo, fleeceflower, and Mexican bamboo. In Japanese, the name is itadori.
Why is the Japanese Knotweed so dangerous? : Japanese Knotweed grows underground and once it takes hold in an area it spreads invasive network of its roots (which is called rhizomes), killing the growth of other plants in the area. Japanese Knotweed acts like a wildfire, once it is introduced to a land it becomes extremely difficult to remove or eradicate this invasive plant. Even if you cut or fire the area, it will reappear in few seasons. It requires a small piece of its root to redevelop the plant and spread across.
These killer weeds grows in the areas which are used or disturbed by humans which includes Lands, House, Gardens, lawns, etc. It can grow from a smallest crack that may occur on roads, drains, pavements and even on large buildings and bridges. It can damage the grave yards and historical architecture or monuments. Moreover the flood defense can also be affected through its growth. The land covered with Japanese Knotweed will be low valued and it can becomes expensive to get rid of the weeds from all over the land.
What are the best ways for Japanese Knotweed control and Treatment? : Japanese Knotweed is very strong and spreads underground, hence the only treatment would be kill its roots. The experienced invasive species specialists or ecological consultant can help in picking the right herbicides and do the systematic ecologically friendly treatment. There are many products available in the market which are labeled as weed and grass killer, containing the most effective ingredient glyphosate. The first step would be to cut the Japanese Knotweed through the season it grows and then inject the weed killer into its stems, which will travel to its roots and stops its growth. These Japanese Knotweed treatment is to be done repeatedly till the plant die, which can take 3 years.
Robin Lawson is an experienced ecologist working with ecological consultants company, on eradication of invasive species since many years, having specialization on japanese knotweed control and treatment.