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Poison Parsley

Posted on June 15, 2012 | 22 comments

Poison parsley is another name for hemlock. Hemlock originally attained notoriety around 2500 years ago when it was used to poison the Ancient Greek philosopher, Socrates. He was executed because his teachings were highly critical of the Athenian state and he was a thorn in the side of various high ranking Athenians. And in those days that tended to limit ones life expectancy.

Hemlock – Conium maculatum

I hadn’t knowingly encountered hemlock until a couple of weekends ago when I was strolling around the RSPB reserve at Fen Drayton, where it was lining the hedgrows in some profusion. It is an imposing plant that was growing taller than me, up to around 2m, it has dark green feathery leaves and white flowers that resemble the hogweeds.

This plant was growing amongst hogweed and cow parsley, and it can appear fairly similar to both, to the uneducated eye.

A variable damselfy (Coenagrium pulchellum) warming itself in the early morning sunshine perched on a hemlock frond

The hogweeds used to provide fodder for pigs, hence the name, but giant hogweed is toxic to humans due to its sap which contains a type of chemical called a ‘furanocoumarin‘ that causes the skin to become sensitive to ultraviolet light. That can result in extremely unpleasant blistering of the skin and blindness if it gets in the eyes. Derivatives of furanocoumarins have been developed as drugs for the treatment of psoriasis.

But the hemlock toxin works in a different way. It is called ‘coniine‘ and the chemical name is 2-propylpiperidine:

I think this compound is remarkable because it is very small for a molecule which has such a specific and catastrophic effect. It exerts its effect by blocking a receptor for a neurotransmitter, acetylcholine, which resides on the membrane on the far side of nerve synapses. This results in a condition called ‘flaccid paralysis‘. Basically, the nerves which facilitate muscle contraction get blocked and stop firing. It starts in the feet and travels upwards, the muscles go floppy and that’s ultimately fatal when the effect reaches the heart and lungs. Socrates’ death was described by Plato and his last words were to his friend, Crito:

“Crito, we owe a rooster to Asclepius. Please, don’t forget to pay the debt.”

The smooth stem of the hemlock plant

The purple spots on the stem of the hemlock are diagnostic, other similar plants don’t have this, so if you see it, admire it, but don’t touch it! All parts of the plant are toxic and it doesn’t take much to have an effect.

The flower head just before the white flowers emerge

Hemlock has a number of names according the the Royal Horticultural Society: California fern, cashes, herb bennet, Nebraska fern, poison hemlock, St Benedict’s herb, snakeweed, spotted hemlock, spotted parsley and winter fern. Also according to the RHS, its range is Europe only, but it has been introduced to the United States, hence the two names which include U.S. states.

Hemlock grows in damp poorly drained soils and is fed on by various insects including caterpillars and occurs in field borders and roadside verges aswell as along the lakes and ditches where I found it at Fen Drayton.

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Posted in Countryside walks, Damselflies, Fen Drayton, Fen Drayton nature reserve, Flora and fungi, Insects, RSPB reserves, UK wildlife, Wild flowers, Zygoptera

Tagged 2-propylpiperidine, acetylcholine, acetylcholine receptor, alkaloids, Anthriscus sylvestris, California fern, cashes, Coenagrium pulchellum, coniine, Conium maculatum, cow parsley, Crito, Fen Drayton, flaccid paralysis, flora, furanocoumarin, hemlock, Heracleum mantegazzianum, Heracleum sphondylium, herb bennet, hogweed, Nature, Nebraska fern, neurotransmitter, plant toxins, Plato, poison hemlock, poison parsley, post-synaptic membrane, psoriasis, RHS, Royal Horticultural Society, RSPB reserve, snakeweed, Socrates, Socrates' final words, spotted hemlock, spotted parsley, St Benedict's herb, variable damselfy, wild flowers, winter fern

More blooming flowers

Posted on June 4, 2012 | 21 comments

Hedgerows, field borders and roadside verges continue to thrive in this part of the world as a result of the recent rainy weather. Nettles are in abundance at the moment, in particular the white deadnettle (Lamium album):

The white deadnettle is, as the name suggests, not a stinger, and it’s common all over the UK, Europe and Asia. It’s white or pink flowers need to be prised open in order to reach the nectar at the back of the flower so only bulky insects such as bumble bees can reach it. It flowers from March to December so it can provide a food source for these insects for most of the year.

According to the Royal Botanic Gardens at Kew, the leaves and flowers can be eaten raw when they are young and tender and the fresh leaves can also be boiled and eaten as a vegetable. The flowers can also be boiled in water and used as a traditional herbal remedy for catarrh and dropsy, which is another name for oedema, or build up of fluid under the skin. The roots can be boiled in wine, which will extract compounds that are insoluble in water into the alcohol fraction of the wine, and the resulting concoction can be used as a remedy for kidney stones. White deadnettle is also used as a herbal treatment for benign prostate hyperplasia, which is enlargement of the prostate gland, and for gastrointestinal problems. So this humble hedgerow plant has the potential to provide a plethora of therapeutic compounds.

The white deadnettle is also known as bee nettle, blind nettle, day nettle, deaf nettle, dog nettle, snake flower and white archangel.

And the other nettle which is springing up everywhere is the much maligned stinging nettle, Urtica dioica:

The flowers of the stinger are tiny and green and grow in strings which are several centimetres long. The stinging mechanism is via hairs, or ‘trichomes‘, and each one has a bulbous end that breaks off when brushed by a passer by, leaving a sharp hollow tube. The tube acts like a tiny hypodermic needle that injects a cocktail of irritant chemicals including histamine and acetycholine which potentiate an inflammatory immune response which is the cause of the stinging sensation. The sting protects the nettle from grazers but also offers protection for other species which are resistant to the sting and the stinging nettle is therefore home to various species of insect and is an important refuge for caterpillars such as that of the peacock butterfly. Before slashing them down in your garden see if you can’t find an out-of-the-way corner to let them grow and provide a home for the butterflies.

Cooking the nettle leaves removes the sting and they are rich in vitamin C so they are used to make soup, herbal tea and, latterly, pesto and in the production of a cheese called ‘yarg‘ from Cornwall.

Charlock, Sinapis arvensis

The yellow flowers of the charlock plant, also known as carlock, corn mustard, field kale, kedlock, kerlock, kinkle, wild kale and wild mustard, have sprung up along the field-side drainage ditches and hogweed, Heracleum sphondylium, is well established too:

Hogweed flowerhead

Hogweed grows all over Europe and flowers from June to August. The flowers burst out of large pods at the top of the stems and are initially pink but fade to white. The young shoots are reputed to be good to eat with a flavour similar to asparagus and the plant gets its name because it was gathered to provide feed for pigs in times past. Hogweed is also known as cow parsnip, cadweed, clogweed, eltrot, giant parsnip, madnep and meadow parsnip.

Pansy, Viola arvensis

Lurking along the edge of the nearby rape fields, almost hidden in the undergrowth, are pansies. The name of the pansy originates from the French word ‘pensee‘ – thought. It is also know as heart’s ease, ladies’ delight and stepmother’s flower.

Hedgerow cranesbill, Geranium pyrenaicum

Hedgrow cranesbill, aka mountain cranesbill, is very common at the moment. It flowers from May to August and it gets it’s name from the shape of the seedpod in some species of geranium which is long and pointed and said to resemble the beak of the crane.

Herb bennet, Geum urbanum

According to the RHS herb bennet also has a number of colourful names: blessed herb, city avens, clove root, colewort, Indian chocolate, minarta, St Benedict’s herb, star of the earth, water flower and wood avens. This plant grows in shaded spots and flowers from May to August. It has aromatic roots which have been used to flavour ale and give off a smell of cloves so it was hung by the door to ward off evil spirits. It was also used medicinally by the Romans as a substitute for quinine.

My day job is in the pharmaceutical industry so I have a professional interest in chemicals which could have medicinal applications either on their own or as cocktails of compounds which may be contained in the same plant. So when I’m researching a post like this I wonder how many species we’ve lost due to modern agricultutal practices and how much herbal knowledge and potential drug molecules have passed into history. Many have probably been lost but there are still thousands remaining to provide us with food, herbs and spices, medicines, and to add the wonderful shapes and colours to the countryside.