Giant hogweed is considered a noxious weed as the sap of giant hogweed can cause blisters, scars and in severe cases, blindness. Like other invasive plants, it was introduced to the UK as an ornamental plant in the 19th century.

Giant hogweed sap can cause blisters and scars if the skin is exposed to sunlight or ultraviolet rays. The first stage of the process is the skin turning red and itchy. Over the next 48 hours, it will start to form blisters, which may lead to scarring. The sap has been known, in particularly severe cases, to cause blindness if it gets into the eyes.


Giant hogweed is a plant that typically grows to heights of 2-5m and has been known to reach heights of 7m. Apart from its size, it very closely resembles common hogweed. It has a dark red/purple stem and spotted leaf stalks. The leaf stalks are hollow and produce sturdy bristles. The flowers produced are white and held in flat-topped clusters that all face upwards and have a maximum diameter of 60cm.

The invasive weed is biennial, meaning that it takes 2 years to grow from seed to fruition and die. It will form a rosette of jagged, lobed leaves in its first year and then grow flowers in the second. Some giant hogweed plants have, however, been known to survive more than two years and flowered in the subsequent years.


Under the Wildlife and Countryside Act 1981 and the Wildlife and Environment (Scotland) Act 2011, it is an offence to introduce giant hogweed into the wild. Although you are allowed to have giant hogweed on your own land you cannot allow it to spread onto adjacent land. The landowner could take legal action against you.

Giant hogweed is a controlled waste and has to be disposed of at a licensed landfill site.


There are two main methods to control giant hogweed:

Spraying – Chemicals are the most effective treatment option but like with other invasive weeds it can take several years to be 100% effective. This is because the seed bank can contain thousands of seeds. The spraying should take place in the growing season (March to August).

Excavation – The quickest method to remove giant hogweed is through excavation. If done by hand extreme caution should be used to ensure that exposed skin does not come into contact with the sap. If the plant has grown above 1 metre tall then it should not be excavated by hand.


If you suspect that you have giant hogweed on your land then contact Wise Knotweed Solutions today or you can contact the team using our contact form.

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