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: Smooth Camas, Cow-grass,Green Lily.
Owing to its coarseness, this species is not eaten by grazing animals to so great an extent as the Death Camas, described later among poisonous pasture plants (p. 50). It is equally poisonous, however, and western farmers have need to be cautious in cutting hay from wet meadows where it grows, for its seeds, which contain most of the poisonous substance, are usually mature at the time the hay is cut. One man, spoken of by Chesnut and Wilcox, used hay cut from a low meadow as winter feed for sheep. At the first feeding many of them became sick, and the rest of the hay could not be used. Considerable amounts of Swamp Camas were found in the hay, and no other poisonous plants were present. In another case six cattle were pastured on low, wet ground and two of them died. The symptoms were practically identical with those caused by Death Camas, and quantities of Swamp Camas were found in the stomachs.
Fig. 6. - Swamp Camas - Zygadenus elegans.
Swamp Camas resembles Death Camas except that it is considerably larger and coarser, and grows in more swampy situations. As stated above, 'the effects produced by the two species are identical. This plant is probably more dangerous in hay than Death Camas, because it is larger and forms a greater proportion of the feed.