As Brits embrace the warmer weather and outdoor activities, Environment Controls, invasive weed specialists warn that even the slightest contact with Giant hogweed can cause severe burns that reappear for years and can even lead to blindness. This highly invasive plant, with its toxic sap that causes photosensitivity, poses a severe risk to unsuspecting humans and pets.

Jennifer Holmes from Environment Controls said: “This dramatic looking plant, found along many a river path, or woodland walk, must be treated with extreme caution. As mentioned above its toxic sap contains furocoumarin, which makes skin extremely sensitive to sunlight and is a danger to humans and pets. Its distinctive flower heads emerge in June – and can be easily mistaken for other plants such as Cow parsley (non-toxic), Hemlock or Hemlock water dropwort (both highly toxic).

“If you touch Giant hogweed you may not notice anything immediately as the effects may take up to 24 hours to emerge, but soon large blisters will form on skin and will recur when exposed to sunlight. As well as its harmful properties, as it colonises river banks this can make it difficult to eradicate – do not try to remove it yourself, always consult an expert.”

Side effects of touching Giant hogweed:

Recurring Blisters

Unlike typical burns, areas affected by Giant hogweed can re-blister each time they are exposed to sunlight, even years after the initial contact.

Eye Damage & Blindness

Direct contact with the sap in the eyes can cause severe irritation, temporary vision loss, and in extreme cases, permanent blindness. This poses a significant risk to curious children and pets.

Delayed Reaction

Symptoms may not appear for up to two days, giving unsuspecting individuals more time in the sun, exacerbating the damage.

Giant hogweed (Heracleum mantegazzianum) is a non-native invasive species listed on The Invasive Alien Species (Enforcement and Permitting) Order 2019. It is an offence to plant or allow it to spread into the wild, as it aggressively takes over habitats. Landowners have a responsibility to prevent its spread, with potential legal consequences, including encroachment fines, if it affects neighbouring properties by allowing it to spread onto their land.

How to spot Giant hogweed?

Height: A very tall biennial or perennial herbaceous plant, capable of growing over 10 feet.
Flowers: Large, white, umbrella-shaped flower heads (up to 50cm wide) that resemble an oversized Cow parsley.
Stem: Thick, hollow, ridged stems that are green with distinctive purple blotches and stiff, white hairs.
Leaves: Large, deeply lobed, and sharply toothed leaves, often reaching over a metre in width.

What should you do if you have a reaction to Giant hogweed?

If you or your pet come into contact with Giant hogweed sap, immediately wash the affected area thoroughly with soap and cold water. Crucially, keep the affected skin out of direct sunlight for at least 48 hours. Seek immediate medical attention if blisters develop, and particularly if sap gets into the eyes.

Due to the persistent nature of its seeds and the highly toxic sap, professional removal is essential. Environment Controls offers expert identification, safe removal, and disposal services, typically using specialist excavation methods to ensure the plant is completely eradicated and doesn’t pose a recurring threat.

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