Growth begins in March and the plant can take 4 years to mature and flower. Each plant can produce as many as 50,000 thousand seeds, which remain viable for up to 15 years. These seeds are easily dispersed by wind and water and also carried on footwear, vehicles or in contaminated soil.

The Problem
Giant hogweed is a potential danger to public health. The stems, undersides and edges of the leaves have small hairs containing poisonous sap, which make the skin sensitive to ultra violet light. By even the slightest touch, blistering, swelling and severe irritation can occur.

Recurring symptoms can last for more than six years. The hairs bearing poisonous sap can even penetrate light fabrics.

The Solution
Control measures are aimed at killing the plant or prevent it flowering. Herbicide application is the most effective means of treatment, although this can take many years, particularly if the plant is well established.

Spraying should start in March when the plant reaches about 1 m in height. These treatments continue throughout the summer and follow-up applications will need to be made in subsequent years to kill seedling growth.

Cutting down stems with a scythe before flowering will help control the plant and flail mowing may also be used but extreme caution is essential to avoid contact with the sap.

Warning

Soil and waste containing Giant hogweed could potentially cause ecological harm and should be disposed of as controlled waste in accordance with official Environment Agency guidance under the Environmental Protection Act 1990, to a suitably licensed disposal site.

Under the Wildlife and Countryside Act (1981) it is illegal to “plant or otherwise cause to grow” Giant Hogweed. The offence is to spread Giant Hogweed, either through actions on site or by transferring contaminated material to a clean area.

Call S H Goss for further details regarding identification, control and disposal.