This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
Other Common Names: Poison Onion, Poison Lily, Poison Sego, Poison Camas, Hog Potato, Mystery Grass, Alkali Grass and improperly Lobelia.
Early explorers in Western Canada learned of the poisonous nature of this plant from the Indians, who had suffered by mistaking its bulbs for those of Camas and Wild Sego, which they used for food. People are still sometimes poisoned in the same way, but the chief harm is done to animals, especially sheep, on the western ranges. In early spring before the herbage is plentiful, the succulent, grass-like leaves look very inviting and are greedily eaten by sheep in spite of their somewhat bitter taste. The onion-like bulbs are equally poisonous, but are not pulled up by the animals, except when a recent rain has softened the ground. Horses and cattle are affected by the poison as well as sheep, but they rarely eat enough to produce serious results. Soon after flowering the plant dries up and in this condition is unattractive to animals. The seeds are extremely poisonous and sometimes produce trouble when the plant is mixed with hay.
It has been established that the poisoning is due to zygadenin, an alkaloid of which the leaves and bulb contain about 0.6%, the root half as much and the flowers roughly 1.25%. The proportions may vary in different localities. The first symptoms noticed in sheep are uneasiness and erratic movements with laboured irregular breathing. Frothing at the mouth, nausea and regurgitation follow, often accompanied by spasms. In the later stages, if sufficient of the plant has been eaten, a complete collapse ensues, the animal lying stretched out as if dead, its shallow breathing scarcely perceptible. Experimental evidence indicates that death is due to a stoppage of the heart's action. Very little digestive trouble is found in adult sheep, but lambs which acquire the poison with their mothers' milk are attacked with enteritis and dysentery, usually dying in a few hours.
Chesnut stated that both horses and cattle are sometimes killed. Pigs are said to eat the bulbs with impunity, and as a result the name "Hog Potato" has been popularly used for the plant. Various remedies such as soda, salt, lard and fat pork, have been recommended and used by stockmen, but with unsatisfactory results. A solution of permanganate of potash and aluminium sulphate gives good results at all stages of the poisoning. It is a chemical antidote, decomposing the poison that remains in the alimentary canal. Whether it neutralizes that which has been absorbed into the system is not apparent. It has, however, led to the recovery of many sheep in which the symptoms were far advanced. Five to ten grains of each chemical dissolved in a pint of water is the dose for a sheep. For horses, fifteen to twenty grains of each should be used, and for cattle thirty to fifty grains. Great care must be taken to have the potassium permanganate completely dissolved. In the case of animals which are prostrated a stimulant such as strychnin produces a slight improvement, but if used alone will not effect a cure. Diuretics, such as caffein or theobromin, are also useful as a stimulant to the kidneys. Care should be taken to keep the animal quiet.
Death Camas is a slender, light-green plant with narrow leaves, five to fifteen inches long, like those of common grasses but more succulent. When young it is often mistaken for a grass, but may easily be distinguished by the fact that there is no ligule where the leaf joins the stem, and by its bulb, which is buried two inches or more in the ground, and resembles a young onion. The flower stem grows from five to twenty inches high and has a raceme of rather small, yellowish or greenish white flowers at its summit.
There are several different species of Zygadenus which grow in similar habitats to Z. venenosus. They all resemble it and produce like effects. They grow abundantly west of the Rocky Mountains, and in the Prairie Provinces and neighbouring States. One of the most common of these is Z. elegans. Pursh (p. 38).