Giant hogweed (Heracleum mantegazzianum)
Giant Hogweed is native to the Caucasus mountains in North Turkey and was brought to Britain in 1893 as an ornamental plant. Unfortunately our climate suits is biology and it is now found throughout the British Isles - usually along river banks. Triffid-like in appearance, Giant Hogweed has a poisonous sap which sensitises human skin and leads to severe blistering. Contact with the sap causes a severe skin reaction known as photo-dermatitis or photo-sensitivity which can recur for many years. It is important that the plant is kept under control, even eradicated where possible. From a river management perspective the biggest problem arises when it forms dense colonies, shading out native plants leaving riverbanks bare of vegetation in the winter and more prone to erosion.
Picture courtesy of LetsGoGardening.co.uk
An example of the blistering after coming into contact with the Hogweed sap. The blisters may re-occur in following years after exposure to sunlight. Giant Hogweed is a phototoxic plant. Its sap can cause phytophotodermatitis (severe skin inflammations) when the skin is exposed to sunlight or to UV-rays. Initially the skin colours red and starts itching. Then blisters form as in burns within 48 hours. They form black or purplish scars, which can last several years. Hospitalisation may become necessary. Presence of minute amounts of sap in the eyes, can lead to temporary or even permanent blindness
We have recently been awarded a grant from the Esmee Fairbairn Foundation of £19,650 over three years to assist in our programme to eradicate hogweed on the Bogie and Isla river systems. This will cover operator and material costs. This will enable us to make huge inroads in the areas that affect the rest of the rivers and we hope that the owners on the main river will do their bit to keep this pernicious plant under control.
The Trust has been controlling Giant Hogweed on the Isla system for 4 years in an attempt to eradicate it which may take as long as 15 years as the seeds lay dormant for many years. Spraying with glyphosate (Round-up biactive) starts in May and continues throughout the summer. Any plants that have emerged later or those that have been unnoticed are cut and a treatment of glyphosate is applied to the stem to ensure the plant dies.
The Huntly Fishing Association have also been spraying Hogweed on the Bogie system.
This time consuming process should eventually bring rewards so that the general public and anglers can access the Deveron without encountering this non- native plant that causes painful blisters when subjected to sunlight.
How to recognise Giant Hogweed
For further information: Environment Agency, Manley House, Kestrel Way, Sowton, Exeter EX2 7LQ and www.nonnativespecies.org
See also the RAFTS Invasive Species and Biosecurity Programme website.