Hemlock Water Dropwort, Oenanthe crocata
Hemlock Water Dropwort, Oenanthe crocata. In flower, Isle of Wight, mid May 2016.
Fancy a curry? I do, and I like foraging for food, but I won’t be using Hemlock Water Dropwort, Oenanthe crocata. Here is a cautionary tale.
About twenty years ago a group of eight young adults on holiday in Western Scotland found what they thought were Water Parsnips growing in a small stream. They picked them and added them to a curry (note 1).
By the next morning, one person, who had eaten more than the rest, was having seizures and other members of the group felt unwell and nauseous. In spite of this, four people ate the leftover curry for lunch and one of this group also had a seizure. Fortunately the police were able to take one of the group back to the stream to collect a sample of the plant, which was identified by a local botanist and following treatment in the local hospital all of the group recovered (note 2).
Hemlock Water Dropwort, Oenanthe crocata, is a fast growing perennial plant of wetlands, streams, ditches and the margins of rivers. It is a member of the Apiaceae (Parsley family) and its flowers are arranged in the family’s characteristic umbels. I have previously written about several members of this family, most recently Wild Carrot (Daucus carota).
There are eight species of Water Dropwort (Oenanthe) in the British Isles, all of which are poisonous. Oenanthe crocata is found mainly in the south and west, including Scotland and Ireland, mainly in lowland areas (note 3). Its stems elongate in spring and it flowers from May to July, depending on location. In 2016 it was flowering on the Isle of Wight in mid May, while in the Oban area in May 2018 the plant was in leaf or in bud. There are some excellent close-up photographs of the plant at different stages of growth on the internet, including the Wildflower Finder and First Nature websites.
It is well worth being able to identify Oenanthe crocata as it is probably “the most toxic plant in Britain to both humans and animals“. Its leaves look lush and tempting and remind me of Flat-leaved Parsley, Petroselinum crispum var. neapolitanum, which I grow on my allotment. Both plants have smooth, hairless stems and leaves and Hemlock Water Dropwort’s leaves have a similar smell to parsley but Flat-leaved Parsley never grows in wet ditches. The lush growth and smell are also a bit like Wild Celery, Apium graveolens, which also grows on wet ground but mostly in the south.
“Oenanthe” is derived from the Greek words oinos “wine” and anthos “flower”, from the wine-like scent of the flowers (note 4). “Dropwort” comes from the (slight) resemblance of some smaller species of Oenanthe to Dropwort, Filipendula vulgaris, which grows in dry grassland and whose root tubers hang like drops from its roots.
All parts of Hemlock Water Dropwort are toxic to mammals. Cattle can eat small quantities of the leaves with no ill effect, but not the plant’s white, fleshy tubers, which are the most toxic part of the plant. They are normally hidden below ground but may be exposed by poaching by cattle, or by flooding or enthusiastic curry-eating foragers. The level of toxins is highest in late winter and early spring, when the plant’s foliage has died down. The tubers are sometimes known as “Dead Mans Fingers” as they typically occur in groups of five or more. They exude a yellowish liquid when cut, which stains the skin.
The main poisonous substance in Hemlock Water Dropwort is a polyunsaturated higher alcohol called Oenanthotoxin. Its direct effects are on the central nervous system, which results in a large number of unpleasant effects, listed here. They range from slurred speech, dizziness and nausea to spasms, acute renal failure and cardiac arrest. The Wildflower Finder website gives more details of the plant’s biochemistry. Research has also been carried out on the plant’s essential oil’s antifungal, antioxidant and anti-inflammatory properties (note 5).
As well as a knowledge of Botany, a knowledge of History comes in handy when you’re sourcing ingredients for a curry. There have been at least fourteen cases of Hemlock Water Dropwort poisoning in the UK in the 20th Century. The Poison Garden website lists a number of cases of poisoning, ranging from a mild (but nonetheless unpleasant) case of poisoning by eating the leaves to stories from the 1970s and 1980s and as far back as the Napoleonic Wars. The latter incident involved eleven French prisoners in Pembrokeshire, two of whom died. John Robertson, the author of the Poison Garden website gives more details in his excellent book “Is that Cat Dead?” (note 6).
One of the symptoms of Oenanthotoxin poisoning is a spasm of the facial muscles known as a sardonic grin (risus sardonicus), although a sardonic grin may also be caused by tetanus, strychnine poisoning or Wilson’s disease. In Sardinia in the pre-Roman Nuragic culture, a “sardonic herb” creating this spasm was used for the ritual killing of elderly people. Italian scientists have suggested that the herb may have been the close relative Oenanthe fistulosa. (O. fistulosa is known as Tubular Water Dropwort in Britain.) (note 7).
Oenanthotoxin is thought to be absorbed through the skin, so try not to splash yourself with the plant’s sap. Artists should heed the warning from the German eighteenth century botanical illustrator Georg Ehret, who found that Hemlock Water Dropwort made him giddy when he was drawing it in an enclosed room. Fortunately his solution – to open the windows to allow fresh air to circulate – was completely successful (note 8).
Although Hemlock Water Dropwort is poisonous to mammals, its flowers are attractive to insects, including Marsh Fritillary butterflies, as photographed by Ray Cannon in Galicia in north-west Spain. My friend Stuart, based in Cornwall where Hemlock Water Dropwort is abundant, tells me that beetles (including flower, longhorn and soldier beetles) and flies (including hoverflies) are especially fond of the flowers.
Hemlock Water Dropwort leaves, looking rather like Flat-leaved Parsley. Near Oban, mid May 2018.
Notes
Note 1: It does make you wonder why they thought this was a good idea. There are two British plants commonly known as “Water Parsnip”, both of which grow by and in fresh water. Berula erecta, Lesser Water Parsnip, is the most widespread and reaches the south of Scotland and Sium latifolium, Great Water Parsnip, is a scarcer Fenland plant. Both are poisonous, although Sium latifolium leaves have been cooked in Italy and its seeds have been used in small quantities as a spice in Scandinavia. The roots are sometimes compared to “white carrots” but apart from the fact that they grow undergound, they don’t look similar to me.
Note 2: Downs C, Phillips J, Ranger A, et al (2002). “A hemlock water dropwort curry: a case of multiple poisoning”. Emergency Medicine Journal Vol. 19: pp 472-473. The article is available online and makes an interesting read.
Note 3: Oenanthe crocata also grows elsewhere in Europe. It has also recently been recorded in the Buenos Aires area of Argentina as an introduced plant.
Note 4: Not to be confused with the bird with the same generic name, the (Northern) Wheatear, Oenanthe oenanthe. The bird is called Oenanthe because the birds return to Greece in the spring just as grape vines are in blossom.
Note 6: John Robertson (2010), “‘Is That Cat Dead?’ and other questions about poison plants”. Book Guild Publishing, Sussex, England. The book is now quite hard to find.
Note 7: Giovanni Appendino, Federica Pollastro, Luisella Verotta, Mauro Ballero, Adriana Romano, Paulina Wyrembek, Katarzyna Szczuraszek, Jerzy W. Mozrzymas, Orazio Taglialatela-Scafati (2009). “Polyacetylenes from Sardinian Oenanthe fistulosa: A Molecular Clue to risus sardonicus“, J. Nat Prod. Vol. 72(5): pp 962–965.
Note 8: Richard Mabey (1996): “Flora Britannica“, Sinclair-Stevenson, London. Page 289.