Hemlock Water Dropwort, Oenanthe crocata

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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

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 5: Valente, Júlia & Zuzarte, Mónica & Gonçalves, Maria & Lopes, Mc & Cavaleiro, Carlos & Salgueiro, Ligia & Cruz, Mt. (2013). “Antifungal, antioxidant and anti-inflammatory activities of Oenanthe crocata L. essential oil.” Food and Chemical Toxicology  Vol. 62.

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.

Gardening For Wildlife

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Regular readers will know that, as well as plants and fungi, I love wildlife. For me, a garden is not complete without its range of wild creatures, ranging from the birds and mammals that visit and sometimes stay for a while, down to the smallest invertebrates that live out their entire lives amongst the plants, in the leaf litter or in the soil.

Our back garden

Our back garden, June 2018

The natural world is under increasing threat from climate change, habitat destruction, pollution and too many humans using too many natural resources. More locally, road and house building, the paving of front gardens and the routine use of toxic substances (in agriculture, by some households and by most local authorities) are all causing harm.

Gardening with wildlife in mind makes our home environment much pleasanter and more interesting but also it helps to provide somewhere for other species to live and thrive.

If you want to read about wildlife gardening, the Wildlife Gardening Forum and the RSPB’s ‘Give Nature A Home In Your Garden’ websites are very good places to start.

Last summer I led a workshop on wildlife gardening and came up with some of my own general principles on wildlife gardening, a couple of which I have written about below. I hope you will find them useful.

What each of us can do in our own garden will depend on our own circumstances, such as the size of our garden, the amount of time we have available and where we live, but these are general principles which can be applied to most gardens.

It All Starts With Plants

When creating a garden it is customary (and sensible) to start with basic structures, such as fences around the perimeter and the position of paths, patios, sheds, washing lines, lawns, ponds and other hard landscaping features. However, from the perspective of wildlife, it is plants that form most of the fabric of a garden and provide shelter and food. For wildlife, it all starts with plants.

Flowers provide food in the form of nectar and pollen and, in return, insect visitors act as pollinators. Recent attention, such as Friends of the Earth’s The Bee Cause campaign has focussed on bees, which include bumblebees and many species of solitary bees as well as the more familiar and mostly domesticated Honeybee. However, other insects such as flies, beetles and wasps, all play their part.

Many kinds of garden wildlife feed on living plants. Leaves can support caterpillars of butterflies and moths, while roots of grasses in the lawn can support charismatic microfauna such as Cockchafer beetles. Some herbivores can be regarded as pests but in a well-balanced garden this only happens rarely (even with slugs and snails).

Cockchafer beetle

Cockchafer beetle

Plants are also the source of rotting and dead material, which is another food source. Dead leaves provide food for earthworms and invertebrates, fungi and bacteria help to break down dead plant matter on the compost heap.

The Wildlife Gardening Forum gives some basic principles for planting but the choice of what to plant is very wide.

Some plants are better for wildlife than others. Highly bred plants with double flowers and/or little or no pollen are of no use to bees and other pollinators, so don’t fill your garden with them. But not all bedding plants are bad – I find that  hoverflies and some solitary bees like trailing Lobelia (Lobelia erinus) flowers.

Avoid invasive flowers which may become a nuisance to you, your neighbours or in the wider countryside. The Wildlife Gardening Forum gives some good advice on this. Beware of invasive pond plants such as New Zealand Pigmyweed. We inadvertently bought it from a garden centre and introduced it into the pond at our previous house and spent two summers getting rid of it.

I personally wouldn’t be without Viper’s Bugloss, Teasels and Oxeye Daisies and don’t find them to be a problem. Stinging Nettles (Urtica dioica) grow in next door’s garden, so I don’t grow them at home because they’re rather invasive, but I’ve found room for a patch at the allotment, where they provide food for caterpillars of Small Tortoiseshell and Peacock butterflies.

I aim to have something in flower from early spring (February or March) through to autumn (October and November) and plants with a wide variety of flower shapes, to attract as many different insects as possible: hardy Geraniums, open-topped flowers like Wild Carrot and long-tubed flowers such as Catmint. (If you read other posts on this blog you’ll see what I like.) I grow a mix of native and non-native plants: both can be good for wildlife.

Sometimes I grow a plant just because I like its spectacular or interesting form, only to find that wildlife quite like it too. I planted Gunnera manicata because I like its spectacular leaves but I found our House Sparrows loved sitting on them and a visiting Fox cub sheltered in the shade the plant one spring. Tetrapanax papyrifer flowers late in the year (and often not at all). But when it does flower, its ivy-like blooms are attractive to Bombus terrestris bumblebees and Honeybees and in the summer insects bask on the leaves. Tree Tobacco flowers are pollinated by hummingbirds and sunbirds in some parts of the world but don’t attract insect pollinators in our garden. However the plant as a whole provides shelter for birds, including Blue Tits and Wrens, which hunt amongst the branches for caterpillars and spiders respectively.

As well as your budget and personal taste, the size and aspect of your garden will have a big influence on what you grow.

It is important to choose the right plant for the right place. Plants like Lavender, Catmint and Perennial Wallflowers like sun or semi-shade and prefer well drained soils. Other plants prefer shade or damp areas, while some will only grow on acid or alkaline soils. While many plants are quite adaptable, there is no point in fighting nature – a Rhododendron will never like chalky soil.

Be realistic with what you might attract to your garden, too. In the Isle of Wight, Ribwort Plantains may attract Glanville Fritillary butterflies, but they are not likely to do so in other parts of the British Isles where the butterfly doesn’t occur. But they may attract other wildlife and if you like growing them (which I do), why not?

Build Up The Layers

When creating a garden, complexity is good. Different animals like using different layers of planting and the more layers the better. Birds are more likely to visit the garden and nest if there are trees and shrubs. While hedges are great habitats, it is often more practical to grow climbers up fences and these can also soften edges  of buildings too.  I grow various climbers, including several varieties of Honeysuckle, Clematis, Chocolate Vine and Chinese Virginia Creeper. I’m a fan of Ivy, but we don’t grow it in the garden as it can be very rampant, though we plan to grow it as an “ivy bush“. When we moved here five and a half years ago, our garden had a lawn, gravel and slabs. We attract birds to the garden by feeding them, but it is only since trees and shrubs have matured that they stay around longer.

It’s worth looking at your garden from the point of view of a bird or insect. What do you need to do to attract different species?

For example:

Bees need food (pollen & nectar), a nest site in a sunny place (holes in walls, logs, hollow stems, snail shells, rough grassland, compost heaps, bare or sparsely vegetated ground bird nest boxes), building materials (mud for mason bees, leaves for leaf-cutter bees, hairy leaves for Wool Carder Bees), sunning places to bask, groom or mate, and sometimes water (such as a pond or bird bath that Honeybees in particular will use to drink and collect water to cool their nest).

Frogs need a pond in which to breed but also the cover of vegetation, where they will spend much of their adult life away from water. A log pile will provide cover for their invertebrate food.

A Blue Tit needs a nesting site (and readily uses nestboxes). Nuts and suet pellets will supplement the adult’s diet but it also needs a good supply of insects, particularly caterpillars, to feed its young. A Blackbird will nest in cover, such as a large shrub, hedge or climber and use a garden lawn as a hunting ground for earthworms. In autumn it will be attracted to berries on shrubs and trees, such as Rowan.

A Holly Blue butterfly will visit plants with nectar. (I’ve seen them feeding on exotics like Curry Plant and Canadian Goldenrod.) But they also need Holly and Ivy plants to lay eggs, where their caterpillars can feed.

Similarly, what does a Violet Ground Beetle, Brown Hawker dragonfly or a Hoverfly need?

Atlas Poppy and hoverflies

Atlas Poppy (Papaver atlanticum) with three different hoverflies, including Episyrphus balteatus (top left) and Dasysyrphus albostriatus (bottom right).

No garden can supply everything, and may only be attractive for part of an animal’s lifecycle, but a garden with a number of layers, plus a lawn and a pond will provide food and shelter for a wide variety of wildlife.

We are building up a decent species list for our garden, including over 350 species of moths, 21 species of butterflies, 37 species of hoverflies, 60 species of bees, nearly 50 species of birds (including ones flying through our air space), Hedgehogs, Smooth Newts, Common Frogs and 7 species of woodlice. It is amazing what is living just yards away from us.

Update December 2019: My wife has started a blog, “Arthropedia“, describing the invertebrates we have found in our garden and further afield.

Saffron, Crocus sativus

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Saffron, Crocus sativus

Saffron, Crocus sativus, with visiting Common Carder Bee, Bombus pascuorum. 8th October 2018.

It’s Saffron season on the allotment, though my ten plants won’t make me a fortune anytime soon.

Saffron, Crocus sativus, is a member of the Iris family, the Iridaceae. There are around 90 species of Crocus, and they are perennial plants that grow from a corm, a short, vertical, swollen underground stem. Crocuses flower in spring, autumn or winter and become dormant in the hot, dry summer months.

We often grow spring-flowering crocuses in our gardens, but Saffron flowers in autumn, as does its relative the very poisonous Autumn Crocus, Colchicum autumnale.

In Britain, Saffron’s leaves start to appear in very late September or early October, barely breaking the soil surface, then the flowers rapidly spring up and open, almost overnight, like fungi. The beautiful purple flower opens to reveal three deep orange female flower parts (styles and stigmas) and three lighter orange-yellow male parts (the stamens). It is the female parts (known as threads) which form the saffron strands we use in cooking. They are picked by hand, even in commercial cultivation. I gently pluck them by hand from my Saffron flowers, leaving the flowers intact. Tweezers are useful but you have to remember to take them with you. On a larger scale, it is easier to pick the whole flowers and take them home to remove the threads. Fresh saffron has no taste, and must be dried and left for about a month before it is used, after which it will keep for at least a couple of years in an airtight container.

Saffron is a very expensive spice, which is not surprising. About 150 flowers are needed to make one gram of dried saffron. (This estimate would require 68,000 flowers to make a pound of saffron; other estimates give 75,000 or even 80,000 flowers to the pound.)

It is hardly surprising that adulteration of saffron can be a problem. In extreme cases, horse hairs, corn silks and shredded paper have been substituted for the genuine article and last year the BBC reported that the synthetic food colourings tartrazine and sunset yellow were used in counterfeit powdered saffron. Marigold petals and Safflower (Carthamus tinctorius) have also been used as adulterants. Even adding the Saffron stamens to real Saffron will dilute the flavour.

We tend to think of Saffron as an exotic spice and much of what we use is imported from Iran (with about 90% of world production), Spain, Portugal, France and India. However, it will grow in some parts of the British Isles. The town of Saffron Walden was a centre of Saffron growing in the sixteenth to seventeenth centuries, before demand fell and the town became a centre for producing malt and barley. Earlier than that, Saffron was probably introduced by the Romans, then died out and was reintroduced around the fourteenth century [note 1]. Nowadays a quick search of the internet reveals that Saffron is grown in several places in Britain, including Norfolk (near Burnham Market), Cheshire, Essex (not far from Saffron Walden) and Devon.

If you want to grow your own saffron, you will need a sunny site with light but fertile soil. Our allotment has sandy soil which, with the addition of some organic matter – I use horse manure – suits the plant well. I did water my plants once this year in late September because it had been very dry, but this often isn’t necessary. The plants are hardy down to -26C but only if the soil is light.

Plant the corms 10 to 15cm (2 – 3 inches) deep and leave a 10cm gap between them. Keep the ground weed free, especially from September onwards. In my second year of growing I have so far found Saffron to be free of pests, but the Saffron Bulbs website lists a few potential problems, as well as giving lots of growing advice. Moving the corms every three or four years (when the plants are dormant) should prevent trouble, after which Saffron Bulbs recommends not using the same area again for ten years.

After flowering the leaves will continue to expand and will stay green through the winter, supplying food to the corm until they wither and disappear in May. Each year, the corms will multiply and already I have some that have doubled up and are producing two flowers. I planted my corms in early September 2017 and had three flowers in the third week of October. This year I have had fourteen flowers from seven plants, from early October, with more on the way. I recommend growing the plant for its beautiful blooms as much as the edible saffron threads. Late season bees and hoverflies seem to like them too: the aroma of fresh flowers in the sunshine is very noticeable even to the human nose.

As well as its use as an ingredient in cooking, Saffron has a number of actual and alleged medical uses. Most promising effects are on the treatment of Alzheimer’s disease, depression, menstrual discomfort and premenstrual syndrome. Sadly, Saffron may not be effective in treating asthma, psoriasis, cancer, stomach gas or baldness. It can also be used as a dye for cloth. However, as it is such an expensive spice, the Plants For A Future website notes that “it is little used at present because cheaper and more effective herbs are available”. The Science Direct website has details of some of the research that has been carried out on the plant and its effects. Active ingredients include picrocrocin and safranal, which give the taste and smell, and crocin, a carotenoid pigment that gives its colour.

Saffron can apparently “provoke laughter and merriment”, which could be useful, but Tournefort’s Herbal [note 1] warns that an overdose may cause people to die of laughing [note 2]. “A lady of Trent… almost shaken to pieces with laughing immoderately for a space of three hours, which was occasioned by her taking too much saffron“. (The WebMD website recommends that you avoid Saffron if you are bipolar.) Large doses of Saffron can cause poisoning and symptoms include  yellow appearance of the skin, eyes, and mucous membranes. More serious are vomiting, dizziness, numbness and bloody diarrhoea and bleeding from the nose, lips, and eyelids. Doses of 12 – 20 grammes can cause death.

The good news is that you’re not going to poison yourself if you use small quantities of Saffron, as in cooking. The BBC Good Food website suggests some recipes, as do the Allrecipes and Rawspicebar websites; a web search will find many more. One of my favourites is Nadine Abensur’s Carrots Braised with Cumin, Saffron and Garlic, which I originally found in my 2004 edition of “The Cranks Bible” – it is a lovely way of honouring home grown, organic carrots and saffron.

Humans have been cultivating Saffron for more than 3,500 years and cultivation probably began in Persia (modern day Iran). The plant is triploid and can only be grown vegetatively. It is not known in the wild but it probably originated from one or more wild Mediterranean species of Crocus, such as Crocus cartwrightianus (from Crete and Greece), Crocus thomasii or Crocus palasii.

Saffron, Crocus sativus

Saffron, Crocus sativus, on the allotment

23/10/2018: Stephen Barstow tells me that, in Palestine, the leaves of Saffron have traditionally been added to food as a condiment. Bulbs of several other species of Crocus have also been eaten (often roasted) in Turkey, Spain, Portugal, Italy and Palestine.

Notes

  1. J.P. de Tournefort, “The Complete Herbal, or the Botanical Institutions of Mr. Tournefort” (1719 – 30). Referenced in “Flowers and their Histories” by Alice M. Coats, published by Adam & Charles Black in 1956.
  2. This reminds me of the Monty Python sketch “The Funniest Joke In the World“, which you can watch on YouTube.