Be aware – danger in the countryside!
The UK’s most poisonous plant is growing in west Norfolk writes Dr Bernard Devereux
A bonus of the very heavy rain we had in early spring is the fantastic display of flowers we are enjoying along our footpaths, highways and byways. Meadowsweet, Cow Parsley and Alexanders line our banks and hedgerows encouraging us out for walks with the kids and our pets.
Unfortunately, one plant which seems to be having an exceptional year due to the wet spring and summer heat is Conium Maculatum - more widely know as Hemlock. This is the UK’s most poisonous plant and all parts of it are lethal if eaten. Touching it is also associated with skin rashes and dermatitis in susceptible people. A member of the Apiaceae (carrot/parsley) Family - eating just a few leaves is considered to be a lethal dose.
Hemlock often grows amidst Alexanders, Meadowsweet and Cow Parsley and at a casual glance can look very similar.
Deaths from Hemlock poisoning have most commonly occurred through mistaking it for other edible hedgerow plants and eating the leaves and seeds. It seems that some dogs are particularly attracted to the roots of the plant and are equally at risk. The most famous victim of Hemlock poisoning is Socrates who was executed in 399 BC by being forced to drink an infusion of the plant as punishment for corrupting the youth of Athens and blaspheming the Gods by his teachings!
Symptoms of poisoning usually appear within thirty minutes to three hours of ingestion. They include dizziness, trembling, fainting, convulsions and irregular heart rate. The poison attacks the central nervous system and usually causes death by respiratory failure. There is no antidote and treatment usually involves placing the patient on a mechanical ventilator and trying to flush the poison out of the system. If you think somebody has ingested Hemlock or is starting to show these symptoms get them to an emergency hospital as soon as possible.
Fortunately, the plant is fairly easy to recognise. It is a biennial producing a low rosette of leaves in its first year which typically grows to five or six feet in its second year. The images show mature plants have smooth, olive-green stems with characteristic purple blotches becoming more frequent closer to the ground. The leaves are finely cut and have an almost fern-like appearance. Flowers are white and very similar to Cow Parsley. Large specimens are usually easy to recognise from the stems but first year plants often lack the purple blotches on the stems so identification relies on the leaves. It has a musty, foetid smell when disturbed.
Of course, the plant has been around for thousands of years and the best way to avoid any problems with it is to recognise it and leave it well alone - making sure to keep yourself and any children or pets away from it. This way you can enjoy relaxed walks along our stunning country footpaths and be sure you will avoid any unpleasant problems.
If climate change causes the weather patterns we have seen recently to become more frequent then it is likely that Hemlock will become increasingly common in our hedgerows and even in our gardens where they border open countryside.
Watch this space for more information about this weed as it becomes available!
Bernard is an Environmental Scientist who is a Life Fellow of Hughes Hall in the University of Cambridge and Fellow and Director of The Institution of Environmental Sciences