Horsetail milkweed, also known as bedstraw milkweed and whorled 

 milkweed, and locally as beeweed, a poisonous perennial herb, ranks 

 among those plants most deadly to range livestock, especially sheep. 

 Asclepias is the Latinized form for asklepias, an old plant name of 

 uncertain identity used by the Greek medical writer, Dioscorides 

 Pedanius; the word is evidently related to Aesculapius (Greek, 

 Asklepios), tutelary god of medicine, and doubtless refers to the 

 plant's putative virtues as a drug. Tournefort and, later, Linnaeus 

 adopted Asclepias as generic name for the milkweeds. The specific 

 name galioides means like Galium, and alludes to the fact that the 

 whorled leaves of this milkweed suggest those of some bedstraw 

 (Gdl-mm}. The English name, horsetail milkweed, recalls the veg- 

 etative resemblance of the plant to some horsetail (Equisetum) and 

 to the characteristic milky sap which exudes from the wounds when 

 the plant is injured. This species ranges from Kansas to central 

 Utah and south to west Texas, Arizona, and into Mexico, being 

 most common and abundant in the United States in Arizona, New 

 Mexico, and southern Colorado. It has been reported as flourish- 

 ing and causing losses near Fallen, Nev., 1 but the broader-leaved 

 Mexican whorled milkweed (A. mexicaiia) , another of the group of 

 milkweeds with whorled (verticillate) leaves, may have been mistaken 

 for it. 



Horsetail milkweed grows commonly on dry plains and foothills 

 at elevations ranging from 4,000 to about 8,000 feet. In the foot- 

 hills of Colorado and New Mexico it apparently prefers the draws, 

 and usually grows along watercourses. It inhabits sandy, clayey, or 

 gravelly soils and ordinarily appears on such overgrazed ranges as 

 bedgrounds and trails, or wherever the vegetative cover is broken. 

 The plants are usually scattered on these areas, and seldom form 

 extensive patches. Occasionally this dangerous plant occurs in hay 

 fields, although that thicker vegetative cover discourages its exten- 

 sive spread or prolific seed production, as essentially it is a sun- 

 loving species. Unfortunately, the growth of this milkweed is not- 

 ably stimulated by cultivation, new plants readily growing from 

 very small root fragments. Irrigation ditches also help to spread 

 the species by carrying the seeds considerable distances to places 

 where the ditchbanks, with their loose soil, furnish ideal conditions 

 for germination and establishment of new infestation centers. 

 Fence rows, abandoned orchards, and broken or fallow fields also 

 have proved sites favorable for horsetail milkweed to grow luxuri- 

 antly, spread rapidly, and form dense, extensive stands. 



Wherever horsetail milkweed occurs, it is a possible menace to all 

 classes of livestock, but fortunately its palatability is zero and it is 

 not eaten except during scarcity of other feed. Cattle and sheep, 

 when cropping this plant by mistake in mouthfuls of mixed herbage, 

 may often be observed to discard it immediately because of its un- 

 pleasant taste. Death has resulted from feeding alfalfa hay infested 

 with whorled milkweed to hungry, poorly nourished animals; the 

 well-fed, vigorous livestock will nose out and reject the milkweed 

 plants from the roughage. May 1 states: "It is very obvious, then, 



1 May, W. L. WHORLED MILKWEED, THE WORST STOCK-POISONING PLANT IN COLORADO. 

 Colo. Agr. Expt. Sta. Bull. 255, 39 pp., illus. 1920. 



