A Plant With A Health Warning
Occasionally you come across information that makes you go ‘Oh My God’ and then ‘Oh My God’ again and this is what was chorused in the office when we came across articles concerning the Giant Hogweed. You might know all about this poisonous giant – and I mean POISONOUS – but if you don’t then continue to read on and be afraid . . . be very afraid.
Identification
Giant hogweed resembles cow parsley or hogweed, with large leaves, spotted leaf stalks and a hollow, reddish-purple stem with fine spines that make it appear furry, much like a stinging nettle. It can grow up to 16ft tall, with leaves as wide as 5ft across. When Giant Hogweed flowers (it can take four years to flower) in June/July it has a 20-inch wide flower head filled with small white blossoms. A single flower head can have 5,000 seeds, with each plant producing up to 80,000 seeds. After shedding its seeds the Giant Hogweed normally dies.
It can be found across the UK, often near rivers and canals as the seeds spread on waterways as well as being dispersed by birds and people.
Originally introduced into Britain in the 19th century by the Victorians as an ornamental plant for lakesides and gardens. “Sadly, once imported, it didn’t stay in the garden, and it was quickly out in the environment, with its seeds floating off along watercourses. You can immediately recognise it because it is much bigger than the native species, and has a thick bristly stem and often purple blotches.” Guy Barter, chief horticultural advisor at the Royal Horticultural Society.
It was in the 1970s that Giant Hogweed gained its notoriety when children started to display blisters as a result of touching the plant’s sap when using the stems to make peashooters.
Toxic Chemicals
Giant hogweed sap contains toxic chemicals known as photosensitising furanocoumarins which react with light when in contact with human skin and can cause effects from a mild rash to watery blisters to chronic dermatitis within 48 hours, all of which require hospital treatment. Effectively the toxic sap prevents the skin from protecting itself from sunlight, which can lead to very bad sunburn and scarring. If accidentally rubbed in the eyes, the sap can cause temporary or even permanent blindness.
If you come in contact with the weed the advice is to cover up the affected area, to prevent the sap from reacting with sunlight and to wash it with soap and water.
UV Protection Taken Away
Contact with the toxic sap from the Giant Hogweed takes all the skin’s natural UV protection away. So when you’ve been blistered as a result of being in contact with Giant Hogweed you’re advised not to allow the skin to be exposed to sunshine for the following 7 years!
Getting Rid Of Giant Hogweed
To deal with Giant Hogweed you need to wear some protective clothing – gloves and overalls – so that you don’t come in contact with the sap. You shouldn’t tackle it on sunny days – wait till it’s cloudy as the sap can only cause injury when combined with sunlight. Seedlings and young plants should be hand pulled; large plants cut down to ground level using secateurs or loppers (not a strimmer) and can be dug out.
When digging out make sure you cut the tap root at least 4” below ground level and shake all the soil from the root. To prevent any possible spread do not take the plant away – and don’t put it in your garden waste bin - ideally let it rot, with the roots exposed to dry out.
Because of the amount of seeds produced by the Giant Hogweed, it can take several seasons to successfully get rid of it.
It’s The Law
Giant Hogweed even has its legislation. The Wildlife and Countryside Act, of 1981 aims to prevent the release of plants such as Giant Hogweed in the first place and to stop them from becoming established. In addition, land owners are expected to take reasonable steps to prevent plants (e.g. hogweed) under their control from escaping into the wild. In certain circumstances, Local Authorities have the power to deal with giant hogweed when it is growing on land.
Bring In The Sheep
A pilot project in Scotland has seen blackface sheep being used as an alternative to the chemical spraying of Giant Hogweed. Blackface sheep have been used as their skin pigmentation gives them protection from the toxic sap of the plant. The project, run in an area beside the Deveron River in Aberdeenshire has seen the sheep successfully graze through a jungle of hogweed and it is now being tested in other areas within Aberdeenshire.