POISONOUS HEMLOCKS THEIR IDENTIFICATION AND CONTROL J . M. Tucker • M. E. Fowle r • W. A. Harvey • L. J. Berry .. POISONOUS HEMLOCKS THEIR IDENTIFI CA TION AND CONTROL THE poisonous 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) How to Recognize Water Hemlock 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, ~ Where Water Hemlocks Grow 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 per acre in suf­ streams, lakes, etc. Salt-marsh water hem­ should be removed before they can be 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 are twitching, of the state from sea level to elevations of areas in the spring when soil is moist; or early summer when the plant is grow­ and the animal may appear to be jumping 7,500 feet or more. 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 Poisonous Properties 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 are flung about wildly, tremely poisonous: two to six roolstocks 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 occur enough Cicuta, but cattle are most often a spring-tooth harrow to drag the root­ of this pest. with frothing at the mouth. Periodically, grazed in areas where Cicuta grows and 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 start the convulsions again. Other Umbelliferae Which May Be Confused With Water Hemlocks CicuJa also contain cicutoxin, and early 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 it will die within 15 to losses. As the leaves expand, however, the occur in wet habitats, may be confused small veinlets ( fig. 3b) . Unlike Cicuta, a 30 minutes after it has shown marked poison becomes less concentrated, and with water hemlock. However, none of definite circle of small bracts occurs at consequently mature leaves rarely cause signs of poisoning.