Giant hogweed (Heracleum mantegazzianum) is a massive 2 – 5m tall plant with leaves more than 1m wide. The leaves are divided and sharply pointed with soft hairs on the underside.
Its stems are large and green with reddish, purple spots. They are ribbed lengthways and covered in bristles.
The flowers open from June to August. They are very small and white, and grouped together in a shape like an umbrella (similar to cow parsley, only much larger).
The plant dies back in early autumn each year but can leave brittle stems behind.
Giant hogweed sap is dangerous to humans. If left on the skin and exposed to sunlight, it can cause massive blistering. Even 7 years later, exposure to the sun can trigger new blisters.
Giant hogweed forms huge stands that block the sunlight from our native plant species, greatly reducing native biodiversity. A single giant hogweed plant can produce up to 50,000 seeds, which disperse by wind, water and human activities.
DO NOT TOUCH giant hogweed! The sap can cause severe skin damage! Everyone operating in infested areas should ensure they are wearing the appropriate PPE to protect from chemical burns.
If sap comes into contact with the skin, WASH with soap and water A.S.A.P. and keep the area away from sunlight for at least 48h. If the sap comes into contact with the eyes, or a reaction occurs, seek immediate medical advice.
If you encounter giant hogweed please enter the details into our log.