Timber poisonvetch, also called greenvetch, timber milkvetch, and 

 timber loco, a perennial herb of great practical and scientific interest, 

 is poisonous in many areas and responsible for heavy losses of cattle, 

 sheep, and horses, but in other areas is grazed without injurious 

 results. This species, a member of the large loco-poisonvetch-milk- 

 vetch (Astragalus) genus of the pea family (Legurninosae), is re- 

 lated to the well-known poisonous crazyweed, or "stemless loco" 

 (Oseytropi-s lambertii). A considerable number of species in the 

 large Astragalus genus are recognized as poisonous to livestock ; those 

 which cause locoism are known as locos, or locoweeds; other toxic 

 species, called poison vetches, produce entirely different symptoms; 

 still other species, called milkvetches, are innocuous. Accurate in- 

 formation concerning the great majority of range Astragali is lack- 

 ing. Until recently timber poisonvetch was usually regarded as 

 harmless; hence the name "milkvetch", so commonly used for this 

 species, was not inappropriate ; in fact, in many localities this plant 

 is considered to be an excellent and nutritious forage species. The 

 late Dr. E. L. Greene (1842-1915), at one time botanist for the 

 Forest Service, is the author of the name cowoollarius, but did not 

 explain it. Perhaps it was because of some imagined similarity of 

 the racemes of this plant to those of lily-of-the-valley ( Con valla ria). 



Timber poisonvetch, so far as is now known, ranges from south- 

 eastern British Columbia and eastern Washington to Montana and 

 south to northern Arizona and Colorado; it probably also occurs in 

 eastern Nevada and northern New Mexico. The plant grows typ- 

 ically on mountain slopes from the oakbrush and ponderosa pine 

 belts to the upper reaches of the spruce zone. In British Columbia 

 it is found at elevations of from about 2,000 to 4,500 feet and in 

 Wyoming between 6,000 and 8,000 feet. It often grows on moist, 

 timbered slopes, in open aspen stands, and along the edges of parks 

 and meadows, thriving on many of these sites, and frequently being 

 conspicuous amidst the plant cover. Although the species grows best 

 on the rich, clayey, sandy, or gravelly loam soils of somewhat shaded 

 sites, it often occurs scatteringly in open, drier sagebrush types. 

 This plant seldom forms pure stands, but usually grows in mixed 

 grass- weed types. 



Timber poisonvetch, unlike many poisonous plants, is palatable 

 to all classes of livestock; the delicacy of its leaves and stems un- 

 doubtedly enhances the readiness with which it is cropped. On many 

 ranges sheep and cattle frequently eat measurable quantities without 

 injurious effects ; sheep on certain areas prefer it to any other feed. 

 Beath and co-workers, 2 as a result of their chemical analyses of tim- 

 ber poisonvetch, state "the crude protein content is * above 

 that of alfalfa." Potentially the plant would rank as highly nu- 

 tritious, an opinion endorsed by many stockmen. 



iThe complex synonymy of this plant includes: A. campestris (Nutt.) A. Gray (1865), 

 based on Homalo'bus campestris Nutt. (1888). not A. oampeatrig L. (1753) ; H. snlidae ; 

 H. tenuifolius ; Phaca convallaria; A. Aecwmbena convallarius; A. serotinus campestris. 

 There are several other very similar Astragali, e. g., A. decumbens, A. divergent, A. hy- 

 lophilus, A. palUscri, A. serotinus, and A. striaosus, which seem more or less to inter- 

 grade with A. convallarius and with each other, and which some authors have regarded 

 as varieties of A. convallarius. Further study of this important and variable group of 

 species is needed to establish definitely the specific limitations and precise geographic 

 ranges. 



2 Beath, O. A., Draize, J. H., and Eppson, H. P. THBEE POISONOUS VETCHES. Wyo. 

 Agr. Bxpt. Sta. Bull. 189, 23 pp., illus. 1932. 



