Zygadenus is popularly known by a great variety of names, death camas being, perhaps, the most familiar. Other common names are poison-onion, poison-lily, poison-sego, camass, hog's-potato, mystery-grass, alkali-grass, soap-plant, squirrel-food, and lobelia. The last mentioned should not be used as it causes confusion with another poisonous plant, the Indian tobacco (Lobelia inflata L.).
The death camas is one of the spring and summer flowers of the West. It is an erect, perennial herb growing from a coated bulb. The leaves are grass-like, long, narrow, and keeled, so much resembling the leaves of a grass or sedge that they are often overlooked in the search for poisonous plants. The flowers are arranged in an elongated cluster or raceme, simple or branched, at the top of the central flower-stalk, which is from ten to twenty inches high, rising above the leaves. The flowers are numerous, small, about one-quarter inch in diameter, yellowish or greenish white, each subtended by a leaf-like bract which is shorter than the slender stalk. The flowers bloom from about the middle of May to the end of July, but the flowering period varies with the season and altitude. The seeds ripen in their three-parted erect capsules in July and August, and germinate the following spring, producing the bulb and leaves only during the summer. The flowering stalk appears the year after. The plants grow more or less as scattered individuals, but sometimes in large masses or patches. These patches of the flowering plants are easily distinguished, even at some distance, by their peculiar greenish-yellow colour.
Zygadenus prows abundantly on many of the stock ranges of the West. It is found generally distributed from Saskatchewan to British Columbia. It is native to Canada.
The poisonous principle of death camas is an alkaloid, zygadenine, allied to veratrine, which is found in all parts of the plant. The toxicity of the flowering tops and the bulbs is about the same, but the seeds are much more toxic than other parts of the plant. Cases of poisoning, however, are more liable to occur early in the season, before the plants are in flower, as at that time the fresh green leaves are most tempting to stock, long deprived of green food. After seeding, the plant withers.
In reference to death camas, T. N. Willing says: "Large numbers of sheep have been affected in the early summer by the prevalence of this weed (in southern Alberta) amongst the grass on which they were grazing." It was proved by the United States Department of Agriculture that cattle and horses were also poisoned by zygadenus, but under ordinary conditions they did not consume sufficient quantity to cause death. The "fatalities were almost entirely confined to sheep."
According to Chesnut and Wilcox, the first signs of poisoning are "a certain uneasiness and irregularity in the movements of the sheep. These irregularities rapidly become more and more pronounced, accompanied by inco-ordination of the muscular movements, spasms and rapid breathing. Although sheep are highly excited under the influence of zygadenus poisoning, the cerebral symptoms seldom constitute a condition of frenzy. It was readily observed that until a few minutes before death, ewes were able to recognize their lambs, and indicate in other ways that they were not in any sense crazed. The later symptoms were those of complete motor paralysis, combined with an exceedingly rapid and sharp breathing and a frequent weak pulse. The duration of these different stages of poisoning varies to a considerable extent, and depends entirely upon the amount of death camas which the sheep have eaten."
The principal symptoms are given by Marsh and Clawson as "salivation, nausea, muscular weakness, coma, and sometimes attacks of dyspnoea."
In general, the symptoms in horses and cattle are similar to those shown by sheep.
Remedy and Means of Control: Medical remedies have been found of little use, as most of the cases are discovered too late for treatment. Rest and quiet are recommended. To prevent loss, it is important to recognize the plant and to avoid pasturing sheep upon it. Hargrave, however, has obtained good results by the use of permanganate of pota.-h and aluminum sulphate administered in the very early stages of poisoning. He says "that for some years past sheepmen in the Walsh District, Alberta, have looked upon potassium permanganate and aluminum sulphate as almost specific in sheep poisoned with this plant, and, especially in cases recognized early, recovery follows in every instance. Some years ago the plant was so plentiful over the range that sheep herders were kept supplied with powders containing five grains of each, and carried with them a pint bottle so that on recognizing any sheep showing effects of poisoning, they at once dissolved the powder in a bottleful of water and immediately administered it as a drench. Very rarely was it necessary to administer the second dose."
In restricted areas, the weed may be exterminated by putting the land under cultivation for a time. After the spring rains, when the ground is soft, the bulbs may be readily pulled, and where the weed is less abundant it would be well worth while to incur the expense of hand-pulling.