by Celia Craske

Created on: August 30, 2006   Last Updated: April 18, 2007

Japanese Knotweed

Japanese Knotweed was introduced into the United Kingdom in the first quarter of the 19th Century from Asia, because it was thought it would be an attractive addition to the garden. Approximately thirty years later, it found it's way to North America.

Today, Japanese Knotweed holds the title of the most pernicious weed in the U.K. Under the Wildlife and Countryside Act 1981, it is illegal to grow it anywhere in the wild or to dump any part of the plant. Any cuttings from the plant can only be disposed of at licensed landfill sites.

The problem with Japanese Knotweed is it's phenomenal growth rate. It can reach a height of 7 feet in a single season with a root system that can spread 7 metres wide and 3 metres deep resulting in any surrounding plants being smothered. A new plant can grow from a piece of root the size of a pea.

The size of the root system means that once the plant is established, it is impossible to dig out. The most effective method of removing it is with glyphosate weed killer although there is talk of introducing insects from Japan who control the plant there naturally.

Even if a plant is successfully eradicated, a part of the root can remain dormant in the soil for up to 22 years before producing a new plant. Where land is found to be infected, the soil has to be removed to a licensed landfill site and buried to a depth of five metres.

Bindweed

There are two species of bindweed, one, Calystegia sepium is a climber with a fairly shallow root system and is easier to eradicate than the other, Convolvulus arvensis which grows along the ground. Both species produce fairly attractive trumpet shaped flowers.

Bindweed can be removed by digging but care has to be taken to ensure that every bit of root is removed. As the roots can grow down to a depth of 15 feet, this is not as easy as it sounds. Furthermore, each section of root will produce a new plant so that trying to get rid of it in this way often makes the situation worse not better as I discovered when I moved to a house where the garden was already overrun with bindweed.

A total weed killer such as glyphosate does a good job of killing off bindweed but it also kills all other plants that it comes in contact with, so it is not always possible to use it.

Couch Grass

Couch grass looks much like any other grass in appearance but it produces underground stems or rhizomes that can choke the root systems of other plants. As with bindweed any small section of rhizome left in the soil will grow

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