Water Hemlock (Cicuta maculata L.)
| Description | Distribution | Conditions of poisoning | Control | Toxic principle | Clinical signs | References
This 2-10 feet tall herbaceous perennial or biennial native of the Umbelliferae family is very difficult to separate from other species of the same family. It has a tuberous root with 2-8 oblong tubers which are 1.5-3 inches long and about 1/2 inch thick at the thickest point near the middle and stem end. The purple-streaked stems are stout and erect with much branching. The stems are solid when very young, but become hollow with nodes where the leaflets are attached. The stems are chambered with horizontal diaphragm of pith tissue which are more closely arranged at the base of the stem. The horizontal plates of piths are most easily visible by cutting the stem base lengthwise.
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| Root of Water Hemlock | Early growth |
The alternate leaves are pinnately 2-3 times compound. The leaves of most species are lanceolate, 2-5 inches long, and sharply toothed. The base of the ong petioles clasp the stem.
Flowers are white and tiny (no more than 1/8 inch across), have 5 petals, and appear in loose compound umbels at branch ends in mid summer. Umbels measure from 2 to 8 inches across and become somewhat spherical in fruit. Fruits are ovoid and ribbed on the outer surface.
New growth begins from tubers as well as from seeds.
The water hemlock occurs throughout the state of Illinois. It is occasionally encountered in wet pastures and meadows and frequently in and along ditches, in the low ground near streams, in low woods, and around ponds and lakes.
Water hemlock is among the most poisonous plants in Illinois. Although the leaves and fruit, either green or dried in hay, can be eaten without danger, a relatively small amount of the tuber will kill a cow in a short time. There is little danger during summer and fall as stock are not likely to browse on the tall coarse plants. But in early spring they will eat the young leaves and stems sprouting from the ground, and in doing so may pull the shallow tubers out of the soft wet ground and eat them also.
In the early spring livestock should not be allowed to graze in meadows infested with poison hemlock, for the young shoots are then springing up and animals can easily pull the poisonous tubers from the wet, soft ground.
Pastures should be free of this plant. It is easiest to remove plants in the early spring. If the plant is not to be removed, it can be kept from spreading by mowing the tops before the seeds form. If extensive marshy areas become infested, it may be necessary to drain the land and cultivate it for several years before animals can again be safely pastured there.
The toxic principle of water hemlock has been called cicutoxin and is a resinoid. It is a thick, yellow liquid with a carrot-like or raw parsnip-like odor. It is concentrated especially in the roots and the base of the stem at or below ground surface. The roots are toxic all year. Young leaves are nearly as toxic as roots, but mature leaves have been consumed in summer and autumn without associated problems.
Ingestion of two ounces of water hemlock tubers can kill a sheep, and eight to ten ounces of mature plant can kill a cow.
The clinical signs of water hemlock poisoning often follow a rather definite sequence. Frothing at the mouth may occur first, but this is quickly followed by uneasiness, frenzied movements, and other evidence of intense abdominal pain. Jerking of the muscles, twisting backward of the head and neck (opisthotonus), together with stiffening of the limbs, dilated pupils, and rolling eyeballs are followed by spasms of the diaphragm (in some species this may be associated with vomiting), convulsions, and death. The poison acts so quickly that the affected animal may die 15 minutes after the first abnormalities are noticed.
Water Hemlock entry in Wikipedia
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