giant hogweed Acorn Ecology

It’s Invasive Species Week!

So here’s our contribution: A species we occasionally come across – Giant hogweed. Luckily, we know that we need to steer clear! It can cause blistering of the skin and scarring if the plant is handled without full protective clothing and gloves.

In the first year of growth it just has leaves and it is not until the second year that it flowers with massive tall flower stems, each one carrying enormous flower heads. Each plant is capable of producing 50,000 seeds!

On development sites we keep an eye open for invasive species, as they can cause delays and other issues on site.

Did you know that we have an online course available? Learn about invasive species in your own time. Find out more HERE.

See this photo comparing Giant Hogweed to Hogweed, our native species. As you can see there is quite a difference in size. The leaves are large and fairly distinctive in the first year and the stems are very hairy, ridged and purple spotted.They can be sprayed with herbicide or dug up and burnt. Dealing with the plant before it goes to seed is the aim as you do not want it to return!

For more advice about invasive species on site call get in touch with your nearest branch:

Exeter – 01392 366512, Bristol – 0117 9232768, Guildford – 01483 382821.


  • Latin Name: Heracleum mantegazzianum
  • Size: Up to 5 m tall, leaves up to 3 m long. The flower can grow to 80 cm in diameter, and the stem 10 cm.
  • Origin: Caucasus mountains, Southern Russia and Georgia
  • Invasiveness: Highly invasive across UK, spreading by seed (wind and water dispersal). A single plant can produce 50 000 seeds. Listed under Schedule 9 of the Wildlife and Countryside Act 1981 in England (it is an offence to plant or otherwise cause to grow in the wild invasive non-native plants listed on Schedule 9 of the Wildlife and Countryside Act). First introduced to the UK in 19th Century as an ornamental plant.


  • Sap can burn skin, even very brief contact will cause blistering after sun exposure. Often leads to permanent increased sensitivity to the sun.
  • Very severe eye irritation, sometimes causing blindness.
  • Outcompetes native species causing reduced biodiversity and loss of native plants.
  • Can cause river bank destabilisation.

The best choice for your wildlife surveys

Exeter: 01392 366512

Bristol: Tel: 0117 923 2768 / Mobile: 07971 994324

Guildford: Tel: 01483 382821 / Mobile: 07443 652988

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