OUR WESTERN MILKWEEDS 



For many years several kinds of milkweed have been looked upon 

 with suspicion or considered poisonous by western stockmen. This 

 opinion was based largely on their own field observations; and little 

 or no experimental work has been done with any of the species except 

 the whorled-leaved milkweed (Asclepias galioides). The latter plant 

 has been carefully studied by ,the Colorado Experiment Station, which 

 was the first of the western stations to show that sheep may be poisoned 

 by this plant when it is eaten either green or dry. (See Bulletins 246 

 and 255, Colorado Agricultural Experiment Station.) Later, C. D. 

 Marsh and his associates of the Federal Bureau of Plant Industry pub- 

 lished the results of their study of the same species. (See Bulletin 

 No. 800, U. S. Department of Agriculture.) 



In the spring of 1918 the attention of the Nevada Experiment Station 

 was first called to our local milkweeds as plants dangerous to live stock 

 when several lambs died after eating the tender, juicy young growth 

 of the showy milkweed (Fig. 4). Since that time the Nevada Station 

 has tested the milkweeds by conducting a long series of experiments 

 in which the plants were fed to both sheep and cattle. More work was 

 done with the narrow-leaved milkweed than with any of the others 

 because it seemed to be our most dangerous species. The result of these 

 feeding tests, together with field observations, are presented in this 

 bulletin. 



Classes of Live Stock Poisoned and the Extent of Losses in this State and 

 Elsewhere. 



Both feeding tests and field observations have shown that the narrow- 

 leaved milkweed (Asclepias Mexicana) is poisonous to sheep and cattle. 

 No feedings of any species of milkweed have been made to horses 

 because there seems to be nothing to show that horses have been 

 poisoned by these plants. 



Because of the limited time since the milkweeds were recognized as 

 poisonous to live stock in Nevada, the extent of losses cannot be accu- 

 rately estimated. Further, unless especially large losses take place, 

 they are usually not reported to the Experiment Station. However, 

 because of the widespread distribution of the narrow-leaved milkweed 

 and the ease with which it kills, it is reasonable to assume that losses 

 of live stock, at least in small numbers, are constantly caused by this 

 common poisonous plant. 



In other States, notably Colorado, Utah, and New Mexico, it has 

 been proven that the whorled-leaved milkweed has caused the death 

 of many sheep. 



Kinds of Milkweed Dangerous to Live Stock in Nevada. 



Several kinds of milkweed grow in Nevada but, from the stockman's 

 point of view, the narrow-leaved species is by far the most important. 

 The other kinds will be discussed briefly toward the end of this bulletin. 

 They are: the Showy Leaved Milkweed (Asclepias speciosa) ; the 

 Heart-Leaved Milkweed (Asclepias cordifolia) ; and the Prostrate Milk- 

 weed (Asclepias cryptoceras) . Our experiments seem to show that the 

 heart-leaved and prostrate milkweeds are not poisonous enough or 

 common enough to be dangerous on the range or in pastures in Nevada. 



