Guernsey has three noxious weeds – spear and creeping thistle, ragwort, and hemlock water dropwort – and the law helps to control them so they do not contaminate agricultural land.
Guernsey States vet David Chamberlain said that while Sark also has its own noxious weed orders, hemlock water dropwort was not included, as it in the past it had not been a serious problem in the island.
‘But for some reason there has been an explosion of hemlock water dropwort,’ he said.
‘We don’t know how it got there – it’s a bit of mystery, although we don’t think there is foul play.’
Hemlock, one of the most poisonous plant in the British Isles, is a large, stout plant between three and five feet high, which flowers in July and is normally grows by streams or douits.
While all the plant is poisonous, it is the white roots, known as ‘dead man’s fingers’ which are particularly toxic.
It is a member of the umbellifer family of plants, which includes celery, parsley, parsnip, and carrots.
Mr Chamberlain said animals would not normally eat the hemlock plant fresh, but with the recent dry weather they may be drawn to douits and streams where it grows.
The plant loses some of its toxicity when it dries out, although it is still poisonous, which can be a problem if it ends up in hay.
‘For humans, the sap can cause skin problems, while ingesting the plant could make someone seriously ill,’ he said.
‘For animals it can give them fits, lose consciousness and die.’
The seeds of Hemlock water droplet are quite heavy, and are carried along streams and douits by the water, rather than spread by the wind.
This means it is important to control the plant upstream, as they will spread downstream.
Mr Chamberlain said there were concerns that as the plant had been found in the upper areas of Sark, where it can spread over the island.
He said that to destroy it safely, the plant should be dried out and then burned in small amounts. If burned when wet, the steam can cause injury.
Mr Chamberlain added that it was important to note the authorities were not trying to wipe out the plants on the noxious weed list.
‘They are an important part of the food chain. For example the yellow and black cinnabar moth caterpillars love ragwort. But the noxious weed laws gives officials an option for how to handle noxious weeds if there is problem.’