HEMLOCK WATER-DROPWORT

Oenanthe crocata

Carrot Family [Apiaceae]

month8may month8jun month8june month8jul month8july month8aug

status
statusZnative
 
flower
flower8white
 
inner
inner8purple inner8
 
morph
morph8hemizygo
 
petals
petalsZ5
 
petals
petalsZcleft petalsZcut
 
type
typeZumbel
 
stem
stem8hollow
 
stem
stem8round
 
stem
stem8ribbed
 
smell
smell8parsley
parsley
toxicity
toxicityZsevere
 
contact
contactZhigh
 

17th June 2011, How Grain, Martindale, Cumbria. Photo: © RWD
Preferentially grows in slow-flowing fresh-water streams and alongside the waters-edge of many canals.


17th June 2011, How Grain, Martindale, Cumbria. Photo: © RWD
Grows up to 1.5m high. Young plants. Leaves only 1- to 2-pinnate, the same pinnateness as other Water-dropworts except for Fine-leaved Water-dropwort (Oenanthe aquatica) which is 2- to 3-pinnate, and Narrow-leaved Water-dropwort (Oenanthe silaifolia) which is 2- to 4-pinnate.


4th April 2015, a brook, Beacon Hill, Appley Bridge, Lancs. Photo: © RWD
A young plant. Old rootstocks can be very thick. Fresh new green growth atop. The roots have white carrot-like cylindrical to ovoidal extremely poisonous tubers (shown near the bottom of this page) containing toxic polyynes which can kill cows if they eat them. The stems contain smaller quantities of this poison and the leaves even less which cattle may eat and get away with without death ensuing. The fruit is also toxic. This plant just does not want to be eaten.


17th June 2011, How Grain, Martindale, Cumbria. Photo: © RWD
Flowers in an a compound umbel in usually 12-40 smooth hairless rays usually 3-8cm long. Bracts immediately beneath the umbel number approx 5 and are linear to trifid. The bracteoles beneath each flower umbellet number 6 or more. Unlike the characterising wider lobes of the lower leaves, the upper leaves usually have narrower lobes. Leaf junctions with the main stem have short sheaths underneath. Young - flowers not fully opened yet.


17th June 2011, How Grain, Martindale, Cumbria. Photo: © RWD
Mostly hermaphroditic flowers (here not yet un-furled). Bracteoles beneath these umbellets number 6 or more.


17th June 2011, How Grain, Martindale, Cumbria. Photo: © RWD
A new branch with a new compound umbel still growing.


17th June 2011, How Grain, Martindale, Cumbria. Photo: © RWD
Six or more bracteoles beneath the flower umbellets, slightly fewer beneath the main umbel.


11th June 2015, Ballymacormick Point, Bangor, Co. Down. Photo: © Lesley Crawshaw
An umbel of small umbellets.


11th June 2015, Ballymacormick Point, Bangor, Co. Down. Photo: © Lesley Crawshaw


6th July 2014, Marshside, Southport, Sefton Coast. Photo: © RWD
Opened flowers have five un-equal white petals, the longer being nearer the periphery of the umbel.


15th June 2015, Ballymacormick Point, Bangor, Co. Down. Photo: © Lesley Crawshaw
The two white stigmas starting to extend in the very centre of each flower.


6th July 2014, Marshside, Southport, Sefton Coast. Photo: © RWD
A white dual-ovary in the centre will form the fruit. Each flower has five stamens with at first red anthers, darkening to a deep purple/violet as they mature.


6th July 2014, Marshside, Southport, Sefton Coast. Photo: © RWD
The red or violet anthers are indicative of Water-dropworts including Hemlock Water-dropwort. Each flower has conspicuous sepals beneath it (which are ovate to triangular, acute and persistent after petal loss), seen better on the two lowest flowers which have lost their petals.


28th July 2015, Ballymacormick Point, Bangor, Co. Down. Photo: © Lesley Crawshaw
An umbel of umbellets of ripened (toxic) fruits.


11th Aug 2015, Leeds & L/pool canal, Parbold, Lancs. Photo: © RWD
A fluted stem leading to one of the main umbels.


28th July 2015, Ballymacormick Point, Bangor, Co. Down. Photo: © Lesley Crawshaw
The two styles have now turned a reddish-purple.


14th Aug 2010, Lancaster Canal, Bilsborrow. Photo: © RWD
Unlike the floret umbels, those when fruiting are not flat-topped, but hemi-spherical.


5th July 2014, Rimrose Valley Country Pk, Sefton Coast. Photo: © RWD
The shape and form of the fruits are the most reliable indicators of the Umbellifers; those of Hemlock Water-dropwort being similarly distinctive. The two styles are long, narrow and parallel or nearly so.


5th July 2014, Rimrose Valley Country Pk, Sefton Coast. Photo: © RWD
The fruits are also nearly tubular, the two melded halves being only a slightly wider across than wide. They are 4-5.5mm long.


6th July 2014, Marshside, Southport, Sefton Coast. Photo: © RWD
The teeth around the top periphery are proportionately slightly shorter than those of other Oenanthe species.
Proportionately, the styles are longer than all other Oenanthe species apart from Narrow-leaved Water-dropwort (Oenanthe silaifolia) (which are both longer, curved and splayed apart, but those fruits are more clearly double-barrelled) and perhaps those of Parsley Water-Dropwort (Oenanthe lachenalli) (which are about equal, but those fruits gradually taper to their base).


17th June 2011, How Grain, Martindale, Cumbria. Photo: © RWD
The leaves are also one of the better identifying features; generally having proportionately wider lobes than do other Water-dropworts.


4th April 2015, a brook, Beacon Hill, Appley Bridge, Lancs. Photo: © RWD


17th June 2011, How Grain, Martindale, Cumbria. Photo: © RWD
Proportionately wide leaflets. Upper leaves are 1- to 2-pinnate, here 2-pinnate.


2015, well above the drift-line, sea-side, Eire. Photo: © Lesley Crawshaw
The highly toxic root tubers (which look similar to parsnips) after they have been washed up on a beech by a storm surge. No one should ever eat these!


11th Aug 2015, Leeds & L/pool canal, Parbold, Lancs. Photo: © RWD
To show the perils in ID when looking at young fruits still developing: these might be interpreted as belonging to Narrow-leaved Water-dropwort because the sepal teeth are splayed outwards before ascending, but these are the young fruits of Hemlock Water-dropwort! Never try to ID umbellifers from un-ripe fruits! Wait until they are fully developed! (Your Author was here misled).


Not to be semantically confused with : Hemlock (Conium maculatum) [another deadly poisonous umbellifer, but one which is not aquatic and is in a differing genus] nor to Dropwort (Filipendula vulgaris) [a plant belonging to the Rose Family]

Can be mistaken for : Parsley (Petroselinum crispum) because the leaves smell similarly, and for Celery (Apium graveolens) because the stems look similar and for the non-native Parsnip Pastinaca sativa because of a resemblance of the tubers.

Easily mis-identified as : River Water-dropwort (Oenanthe fluviatilis) but that has the lower leaves submerged in the water.

Slight resemblance to : Corky-fruited Water-dropwort (Oenanthe pimpinelloides), Narrow-leaved Water-dropwort (Oenanthe silaifolia), Parsley Water-Dropwort (Oenanthe lachenalii) but the pinnate leaves of all three of these have narrow linear leaflets on at least some of the pinnate leaves, but not all.

Superficial resemblance to : Fine-leaved Water-dropwort (Oenanthe aquatica) but the lower submerged leaves are 3- to 4-pinnate and the upper leaves 2- to 3-pinnate and finely divided leaflets.

The white tubular shaped fleshy tubers are the most toxic, especially in late winter and early spring. There are typically five or more which gives rise to their alternative name of 'Dead Mans Fingers' (not to be confused with Xylaria polymorpha, a fungus with the same common name). When cut they exude a yellowish liquid which stains the skin. It is one of the most toxic plants in the UK. Cattle may safely graze the leaves, providing they do not consume too much, but if they perchance get to eat tubers may well die. The tubers, of course, are normally below earth and inaccessible to cattle but may become exposed by pulling or dredging operations or by scouring of the stream/river bed during floods.

It is a perennial and a lowland species growing below 300m, flowering in June to July. Habitat is shallow freshwater streams and slower flowing rivers, lakes, ponds, canals, marshes, fens, flushes and wet woodlands. They are often found near the coast in more brackish waters, but never in the sea itself.

POLYYNES

The principle toxin is a polyyne of which only very small amounts are sufficient to cause death. It is a convulsant poison, a neurotoxin; in horse and cattle the displayed symptoms include salivation, mydriasis, respiratory distress followed by spasmodic convulsions usually leading to death. Cattle that survive may develop diarrhoea for a couple of days and then slowly recover. Pigs vomit and die suddenly, but 50% of sheep may recover. The leaves will poison humans if eaten in mistake for parsley, and deaths have resulted, or the stems for celery or the tubers for parsnips. It was once used by farmers to control rats and moles.

The leaves smell of parsley or celery but at least those are the least poisonous of the parts of this plant but folk have still died eating them. The stems contain less of the toxins than the tubers, but more than the leaves. The toxin seems able to enter the body through the skin, so care should be exercised when handling it, particularly any sap.


The main highly toxic constituent is a polyyne called Oenanthotoxin, a poly-unsaturated higher alcohol, with two strained triple bonds. The highest concentration is contained within the tubers; less within the stem and less still within the leaves, although there have been fatalities with folk eating the leaves. The toxin is also reputedly able to infitrate the skin, so the casual examiner of the plant should be careful, especially with any sap.



The dihydro derivative of Oenanthotoxin is present at approximately 10-times less concentration. DiHydroOenanthotoxin has one less double bond, two rather than three. This is also highly toxic.



Oenanthotoxin is isomeric with the polyyne Cicutoxin, where the third double bond has moved to another location on the molecule adjacent to the two others. Cicutoxin is the toxin present in Cowbane (Cicuta virosa) another convulsant poison, but is not present in Hemlock Water-dropwort.

The essential oil of Hemlock Water-dropwort contains mainly monoterpene hydrocarbons at 86%, the main compound being trans-β-Ocimene at 31%, followed by Sabinene at 29% and the cis-isomer of the first, cis-β-Ocimene at 12%. These presumably impart the parsley-like aroma to the plant.


  Oenanthe crocata  ⇐ Global Aspect ⇒ Apiaceae  

Distribution
 family8Carrot family8Apiaceae

 BSBI maps
genus8Oenanthe
Oenanthe
(Water-Dropworts)

HEMLOCK WATER-DROPWORT

Oenanthe crocata

Carrot Family [Apiaceae]