POISONOUS HEMLOCKS
THEIRIDENTIFICATION ANDCONTROL
J . M. Tucker • M. E. Fowle r • W. A. Harvey • L. J. Berry .. POISONOUS HEMLOCKS THEIR IDENTIFI CA TION AND CONTROL
THEpoisonous plants referred to in this publica tion as "hemlocks" are members of the carrot or parsley family, Umbelliferae, and should not be confused with true hemlocks, which are coniferous trees of the pine family, Pinaceae. Poisonous hem locks are of two genera: Conium (Poison Hemlock), and Cicuta {Water Hemlock). They have a general family resemblance to one another but are not closely related; their toxic properties and effects are different, they present different problems to the live stock industry, and they have different diagnostic features.
THE AUTHORS: J.M. Tucker is Professor of Botany and Botanist in the Experiment Station, Davis; M. E. Fowler is Assistant Professor of Veterinary Medicine and Assistant Veterinarian in the Experiment Station, Davis; W. A. Harvey is Extension Weed Control Specialist, Agri cultural Extension Service, Davis; L. J. Berry is Range Manage ment Specialist, Agricultural Extension Service, University ol California, Davis.
OCTOBER, 1964 ------WARNING------2,4-D is classified as an injurious material, by the State Department of Agriculture, and before it can be purchased or used a permit must be obtained from the County Agricultural, Commissioner. It should be used with care and at a time and in such a manner that it will not drift to other plants or properties and cause injury to susceptible plants or result in an illegal residue on other food or feed crops.
THE GROWER IS RESPONSIBLE for residues on his own crops as well as for problems caused by drift of a chemical from his property to other properties or crops.
Fig. I. Mature plants of water hemlock (Cicuta). General Characteristics of Umbelliferae
The family Umbelliferae, which includes serve as characters for identification. In poison hemlock, also includes carrot, cel order for a botanist to make a positive ery, and parsnip, and herbs such as pars identification on an unknown species of ley, anise, dill, caraway, and coriander. Umbelliferae it is usually necessary to The leaves are usually much divided and have the mature fruit for examination. fern-like, and are alternately arranged Although illustrations of the fruits of all @ \ along the stem ; in some members of the groups discussed herein are included to family ( carrot and poison hemlock, for aid the reader, more emphasis is placed example) the first year's leaves are in a on other identification features for two basal tuft. The base of the Ieai-stalk is reasons: most livestock losses from hem usually somewhat enlarged and partly locks occur long before mature fruits de surrounds and clasps the stem. The nu velop and the rancher cannot wait 2 or merous, small flowers are borne in um 3 months for an identification, and be brella-shaped clusters (umbels) . A circle cause mature fruits are generally small, © of bracts (small, leaf-like structures) a strong magnifying glass or a good hand called an involucre is usually present lens is required in order to study tl1em. around the base of the umbel (fig. llc). Fortunately, Conium and Cicuta show The small, dry fruit of these hemlocks good diagnostic features in other organs often shows distinctive features which can much easier to observe.
WATER HEMLOCK (Cicu,fa) Howto RecognizeWater Hemlo ck
There are two similar water hemlock nately compound. The individual leaflets species in California: western water hem ( the ultimate divisions of the leaf) are lock ( Cicuta douglasii) and salt-marsh lance-shaped, and have regularly serrale water hemlock ( Cicuta bolanderi) . They margins (fig. 2b). Also, the leaflets show are smooth, erect perennials, 3 to 8 feet a distinctive venation pattern: the sec tall, with hollow stems, and short, thick ondary veins usually extend from the mid ened, basal rootstocks (fig. I ). In large rib out to the notches between the mar mature plants, the rootstock is divided in ginal teeth (fig. 2c), whereas in most ternally into a series of hollow chambers other genera in the family the secondary by cross-partitions which are readily ap veins run out to the tips of the teeth. parent when the rootstock is cut open Water hemlock does not have a circle of ® ® lengthwise (fig. 2a). When this is done, bracts surrounding the base of the umbel drops of a yellowish, oily liquid ooze out as in most members of the family ; only upon the cut surface, and in a matter of one or nvo small bracts may sometimes minutes the liquid turns reddish, and then be found. The numerous, small, white reddish-brown. This liquid, which has a flowers are grouped in compound umbels. distinctive, aromatic odor, contains the The fruits, which are about ¼" to 3/16" poison of the plant-a resinous substance long, are dry when fully ripe and each called cicutoxin which is soluble in splits readily into two halves (a charac organic solvents but not in water. teristic of the whole family). Fruits are \ The leaves are large and much divided, broadly oval, or roundish and slightly and are once, twice, or three times pin- flattened (fig. 2d). jRR Fig. 2. Water hemlock (Cicuta). A- rootstock cue lengthwise, 80 per cent actual size; [4] B- leaf, 25 per cent actual size; C- Jeaflets, showing distinctive venation pattern, 80 per cent actual size; D- fruit, 7 times actual size. Inset is actual size, ~
WhereWa ter HemlocksGrow on finding that the plant has been eaten the soil. This may be done by levelling, stocks should be collected, dried, and Water hemlocks are restricted to wet and perhaps finding parts of the root improving drainage, and realigning · burned -as described above. habitats-marshy areas, the borders of stocks in the rumen or paunch. ditches; rootstocks brought to the surface 2,4-D sprays have given good control, The first signs of poisoning may be using 2 pounds of 2,4-D acre suf streams, lakes, etc. Salt-marsh water hem should be removed before they can be per in lock is found in salt marshes along the seen from 10 to 60 minutes after the plant eaten by livestock. ficient water to give complete wetting of coast in central and southern California, is eaten. The animal walks stiffly and acts Hand-grubbing of scattered plants, the water hemlock's foliage; a low-volatile uneasy. The eyelids may begin to twitch. or in brackish marshes around the var mechanical cultivation, and chemical ester of 2,4-D, or an amine formulation In a few minutes the muscles of the neck ious arms of San Francisco Bay. Western sprays, can control the pest. Hand-grub with an added wetting agent, can be used. begin to twitch and may cause the head water hemlock occurs throughout most bing or digging is usually done in small Spraying should be done in late spring to jerk ; soon many muscles twitching, of the state from sea level to elevations of are areas in the spring when soil is moist; or early summer when the plant is grow the animal may appear to be jumping 7,500 feet or more. and plants can often be pulled from moist soil ing vigorously but before its seeds ma up and down. As the muscles continue to with a minimum of digging. Care should ture. Grasses are not damaged by 2,4-D PoisonousPropertie s contract the animal falls down, goes into be taken to remove all the rootstocks in they will usually fill in spaces occupied by violent convulsions, and fights for its The rootstocks of these plants are ex the soil, as remaining pieces can sprout the hemlock and so help prevent regrowth breath. The legs flung about wildly, tremely poisonous: two to six roolstocks are and form new plants; rootstocks should and reinfestation. A follow-up treatment the neck may be arched down between on regrowth in the fall or the following (½ to 1 pound) can kill a mature cow be placed in bags or boxes and carried in as little as an hour. Dried rootstocks the legs or pulled backwards, and the from the field to be dried and burned. spring should be planned; spot spraying third eyelid is frequently pulled over the Larger infestations may be plowed and of any water hemlock appearing in sub are as poisonous as fresh ones. All animals (including man) are poisoned if they eat eyeball. The mouth and face become con thoroughly harrowed several times with sequent years should keep the area free torted and violent chewing motions occ enough Cicuta, but cattle are most often ur a spring-tooth harrow to drag the root of this pest. with frothing the mouth. Perio cally, grazed in areas where Cicuta grows and at di stocks to the surface. The exposed root- the animal will relax and lie quietly for are more likely to pull up the rootstocks from wet ground. The young leaves of a moment, but a slight noise or touch will the convulsions again. OtherUmbelliferae Which May Be ConfusedWith Water Hemlocks CicuJa also contain cicutoxin, and early start in the growing season may cause livestock If the animal falls down and goes The following plants, which commonly Cicuta) but become lost in a network of into convulsions will die within 15 to losses. As the leaves expand, however, the it occur in wet habitats, may be confused small veinlets ( fig. 3b) . Unlike Cicuta, a 30 minutes after has shown marked poison becomes less concentrated, and it with water hemlock. However, none of definite circle of small bracts occurs at consequently mature leaves rarely cause signs of poisoning. An autopsy of the dead them has the same combination of char the base of the umbel. animal will not give much he unless poisoning. lp acteristics so distinctive of Ciczita: the Water parsnip grows in marshes and Cases of livestock loss from eating parts of Cicuta are found in the rumen chambered rootstock in large, mature along sloughs from central California Cicuta have been fairly common in Cali the poison affects the brain so quickly that plants; the oily, aromatic liquid exuding northward into British Columbia. Al fornia. The most serious occurrence to no lesions are produced. Animals that from cut surfaces of the rootstock; the though reportedly toxic to livestock, there have eaten only small amounts of Cicnta come to our attention in recent years was secondary veins of the leaflets running to appear to be no authentic cases of its hav during the winter of 1961-62, when twen may show mild signs and live. the notches between the teeth rather than ing caused livestock loss. ty-seven cattle died on a ranch in Del into the teeth; and the lack of a circle Norte County. These animals had been Treatment of bracts at the base of the umbel. Water parsley, Oenanthe sarmentosa feeding on swampy land which had been Because there is no specific antidote for ( fig. 4). Water parsley is a lower-growing cleared and seeded to grass; it is probable Cicuta poisoning, and because death Water parsnip, Sium suave ( fig. 3) . plant than water hemlock, and is com· that Cicuta was the cause of death, as the usually occurs too quickly for anyone to This plant is more similar to water hem monly 2 to 4 feet tall. The stems are softer area was found to be heavily infested with treat the animal, prevention is the only lock and can be more readily confused and more succulent than those of water the plant and pieces of its rootstock were hope in controlling losses from poisoning. with it than can any of the others listed hemlock; the leaflets are more coarsely found in the rumen of two of the dead The rancher must recognize the plant and below. I ts leaves are only once pinnately toothed and often deeply cleft or divided animals. eliminate it, or keep livestock away compound (fig. 3a), however, while ( fig. 4b) , unlike the evenly serrate leaflets from it. water hemlock leaves are usually two or of water hemlock. Mature fruit is 3/i.6 of Signsof Poisoning three times pinnately compound (fig. an inch or less in length, barrel-shaped Cicnta produces such a rapid death that ControllingWater Hemlock 2b) . The venation pattern of the leaflets to cylindrical, and µas conspicuous in most cases illness will not be observed. It is often possible to reduce water hem is quite different; the secondaries are elongated styles (fig. 4c) . Animals may be found dead near the lock infestation and improve growth of rather weak and irregular and do not Water parsley grows mainly along the source of the plant, and diagnosis is based more desirable forage species by drying extend directly to the margin ( as in coast from southern California into [ 6 J [ 7] ~
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Fig. 3. Wa ter parsnip (Sium suave). A- leaf, 25 per cent actual size; :&-leaflet, showing vena tion pattern, 80 per cent actual size; C-fruit, 14 times actual size. \ Fig. 4. 'Water parsley (Oenanthe sarm~ntosa). A-leaf , one-third actual size; :&-leaflets, Canada, and in the northern Sierra further distinguishing it from water hem 75 per cent actual size; C-fn1it, 12 times actua l size. Nevada. lock. Cut-leaved water parsnip, Berula Cut-leaved water parsnip grows in spects. The base of the leafstalk of the The umbel is finely woolly, unlike water erecta (fig. 5). This plant is 10 inches to marshes and along sluggish streams upper leaves is enlarged, and has an in hemlock, and the flowers are in den&e 30 inches tall, and has leaves only once throughout most of California. I. flated appearance; the leaflets are usually ball-like heads (fig. 6c). The fruit is pinnately compound, whereas those of White heads, Sphenoscwdium capi more irregularly toothed than those of flattened, and has a narrow marginal water hemlock are two or three times tellatum (fig. 6). An erect plant 3 to 5 water hemlock, and the inconspicuous wing on either side ( fig. 6d). pinnately compound. A circle of small feet tall. Similar in a general way to water secondary veins run into the teeth rather White heads occurs along streams and bracts occurs at the base of the umbel, hemlock, it differs in a number of re- than to the notches between the teeth. in swampy places in the mountains of [ 8] [ 9] ..
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:-:. ® ':· \ Fig. 5. Cut-leaved water parsnip (Berula erecta). A-leaf, 60 per cent actual size; :B leaflet, slightly enlarged; C-upper leaf, 60 per cent actual size; D-fruit, 18 times actual size.
',) © California, at altitudes ranging from habitats. Individually, they differ from . f) l:• 1·.· \ 1-, . \ 3,000 to 10,000 feet. water hemlock in various ways, hut in all Angelica, Angelica species (fig. 7). of them the fruit is conspicuously differ Fig. 6. Whit e heads (Sphenosciadium capitellatum). A-leaf , 25 per cent actual size; Some species are somewhat similar to ent, having thin flattened margins on :B-leaHets , 80 per cent actual size; C-flower cluster, two-thirds actual size; D-fruit, water hemlock, and a few occur in wet either side (fig. 7c). 9 times actual size. [ 10] [ 11 ] POISON HEMLOCK (Conium) Howto RecognizePoison -Hemlock There is only one species of poison hem on it. Conium is not nearly as dangerous lock in California, Conium maculatum as Cicuta because the animal must eat I (fig. 8), a branching biennial commonly to 2 per cent of its body weight to produce 4 to 6 feet tall, but sometimes attaining a poisoning, and even then the animal may height of 10 feet. I t has a long, white, recover if given proper care. often-branched tap root; the stem is stout, hollow, smooth, erect, and marked with Signs of Poisoning © reddish-purple spots (fig. 9)-the spotted Poisoning signs appear 2 to 4 hours stem is one of its most distinctive features. after eating the plant. Conium affects the Lower leaves are I to 2 feet long or more, animal's brain; the animal loses strength, •IU/,1," ,' : much dissected, and fern-like. The small, its hind legs buckle beneath it, and it tW1v ::(·:i I rl ~-~ white flowers are arranged in open, com staggers and falls. It may get up again ;_~- 1 I/ :, ._:. ' f • ~ ,. ~ ,_, . . . 1r, -;_,..;<" 1,~w11 /I··. 'l' •l(,1 ~ - pound umbels, 3 inches or less across. A with difficulty, or it may stay down. The 1 I ·-~ 7 circle of small, simple bracts surrounds front legs soon become paralyzed and the fhN•" (l '.i tLf r ! , 6 the base of the umbel (fig. 10c). The animal appears drowsy and goes into a it;i:: l ··riw, small fruits are oval, and when dry have coma. An animal may be down and I, ribs that are minutely but distinctly paralyzed for a day or two and still re :l1 ~ - lj '71 (under a magnifying glass) wavy or un <:over. Death can occur in 5 to 10 hours / , ~}~:=-· dulating (fig. 10d) . Like water hemlock, after these signs are noted, and autopsies :~ ~~ '1. the fruit splits into two halves when fully reveal nothing significant. ripe. ~ . Treatment @~ ~ Where PoisonHemlock Grows There is no specific antidote for Poison hemlock, a native of Europe, Conium poisoning, but keeping prostrate occurs at lower elevations throughout animals shaded or warm and providing much of California. Unlike the water feed and water will save most of them. hemlocks it is not semi-aquatic, and al Laxatives may help to remove the @ though frequently found in moist ground material from the rumen; do not drench ® it may thrive in fairly dry soil. an animal in a coma, as a fatal pneumonia ~K may be produced. PoisonousPropertie s Conium has been recognized as a poi ControllingPoison Hemlock _-3::?~ .. = sonous plant for many centuries. Its Poison hemlock occurs in wet and in r.·, I ~ .. . ~r-'~~ poisonous principle ( consisting of several drier portions of fields. If the area is wet, alkaloids) is found in the green leaves improved drainage may help the growth and stems and the fruit of the plant. of desirable pasture plants but will not Owing to the volatile character of the eradicate tl1e poison hemlock. However, \ poisons this hemlock largely loses its frequent close mowing will eliminate an infestation by preventing seed formation. F ig. 7. Angelica (Angelica). A- leaf, 25 per cen t actual size; B- leaflets, half size; toxicity on drying. Thus, hay containing C- fruit, 7 times actual size. Conium is not dangerous. Close mowing also reduces the amount of The plant is rarely eaten, but if whole green vegetation available for grazing, some forage is lacking livestock may eat and the dried mowed material rapidly the young foliage with fatal results. In loses its toxicity. rare instances, the small seed-like fruits Poison hemlock can also be controlled may occur as an impurity in grain in by spraying with 2,4-D in late spring sufficient quantity to poison livestock fed while the plants are growing vigorously [ 1-2 ] [ 13] ;tA "'
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Fig. 8. Mature plants of poison hemlock (Conium maculatum). Fig, 9. Spotted stem of poison hemlock (Cotiium maculatum), .,
( old, dry plan ts are not controlled by this tions, treatment each spring for several treatment). Ester or amine formulations years is necessary for complete eradica of 2,4,-D, at 2 pounds per acre in sufficient tion. Improvement of desirable forage water to give thorough wetting, will give plants through pasture management, fer control. Some re-treatment is usually tilization, irrigation, or drainage will help necessary because of missed plants, new to prevent reinfestation. seedlings, or regrowth; in heavy infesta- @
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\ © Fig. IO. Poison h emlock (Conium maculatum). A-leaf, 20 per cent actual size; B Fig. 11. 'Wild carrot (Daucus carota). A-leaf, half size; B-por tion of leaf, two portion of leaf, one-third actual size; C- flower cluster, actual size; D-fruit, 6 times thirds actual size; C-fiower duster with involuc.Te at its base, two:thirds actual size; actual size. D-fruit, 7 times actual size. [ 16] [ 17 J !.~t~d ~ ~:--;\/;ti~:{~;;t{'~:~f¥i-:~, :-. ,,J , ~ ~ · ,-~, \ • -~ • ~>, • •• i::;••-. •.: OtherUmbelliferae Which May Be ConfusedWith Poison Hemlock ... ~-,, ...-t , -~:.-J :· ,\!°'j:!, ~- •., / ' l -~· .._~_~::. ! .. • · • '~ - · . .. .• ·• •l • J f ·· '-'~~;dk ' J.3 .. ,.'/ .'/ -=-~!y . .· , ,, ~i The fo llowing plants could be coniuscd Bishop's weed, Ammi majus (fig. wilh poison hemlock, although they do 12) . An erect biennial, 1 to 21/2 feet tall, li ,,- with smooth, branched stems. The lower A~~ ~\\ ii~ ~ not poss1•ss the combinalion oI characters cli slincli \'C of poison hemlock: the red leaves (fig. 12a) are pinnntely compound ~ , cli i;h-purple spotting on the stems, the with lanrr-shap<'d leaflets having very circle oI small, simplr bracts, and the finely and sharply serrate margins, quite wavy ribs on the fruil. unlike the lca,·c,; of poi~on hemlock. The Wil -~~~ - ® @ Co•'•l'f'Ulh t- E-.:lfnfton wo,k in Ac;ri-cultu1e aod HoMt- t:nu10in1it"~ l..ollf'e" nr •" grk11h11tf", Unh'CnilJ of California. a,i,d C aitNI S 1a11-.. l)ppsrlMMI of " va,t"Uhure !'~ (0 o p1"rnt111g. 01~1,lbu 1ed in !urthu·anc::eo f 1ht" A r i:- or ( 011~, c-~, o f )b! ' 8, ;uul J une 3V, J9H , Ccori;;c D. Alcorn, Uill.'('10t , C::iilifv111i :a Alirr• uhur.11 E\IC'nnon 5ctl'ieO. I I 1,~,,,1 \ 12lm· I0 ,"64 (BM 16 ) V . L. Fig. 12. Bishop's weed (Ammi majus). A-low er leaf, 60 per cent actual size; B--Ieaf ···~ midway up the stem. 60 uer cenl a<:l.ua l .Qi7l'! ('_,,, ,,..,.r ,,.,.,. RO n~•· ~~-· -M·-- 1 ·=--·.,.,. E GOOD ... is the abundant earth. To achieve it, vast knowledge is needed now-and more will be required as expanding populations continue to make even greater demands upon the earth's resources. How are scientists, researchers, and agriculturists developing and implementing knowledge which will make the good earth flourish for future generations? In part, the answer will be found in the many pub lications put out by the University of California's Division of Agricul tural Sciences. Among these publications are: ◄ theBULLETIN series .. . designed for an audience of scientists, and for informed lay men interested in new research. the CIRCULAR series ... intended for a► popular audience, and offering extensive dis cussions of some phase of an agricultural operation ◄ CALIFORNIAAGRICULTURE ... a monthly magazine describing latest research in the Division of Agricultural Science, and designed for researchers, informed farmers, and agri-businessmen LEAFLETS ... these are short circulars de-► s/gned to answer one or a few questions for the home-grower or farmer without giving · detailed background information For a cata log of publications, w rite Agricul tural Publications, 207 University Hall, University of California, Berkeley, Calif. 94720