Rubber rabbitbrush, a deep-rooted, perennial shrub growing 20 

 to 40 inches high, is a member of the aster family (Compositae) and 

 is commonly known simply as rabbitbrush. However, the addition 

 of the word rubber to the name is appropriate as this species con- 

 tains a high grade rubber called chrysil, which vulcanizes readily. 1 

 Chrysothamnus is from the Greek chrysos (gold) and thamnos (a 

 shrub), referring to shrubby plants with golden-yellow flowers. 

 The specific name nauseosus refers to the disagreeable flavor of the 

 herbage. The range of rubber rabbitbrush extends from British 

 Columbia and Alberta south to Wyoming, Utah, Nevada, and eastern 

 California, 



Rubber rabbitbrush is very common, and in some localities is one 

 of the most characteristic plants in the plains, foothills, and inter- 

 mountain valleys. It grows on the open sites of the sagebrush, 

 juniper-pinon and ponderosa-pine zones and inhabits dry, sandy, 

 gravelly, or heavy clayey and alkali soils. Rubber rabbitbrush is 

 commonly associated with sagebrush, saltbushes, and various grasses 

 but most frequently grows in dense stands varying in size from a 

 few acres to several square miles. It is often found along roads, 

 fences, and in waste places adjoining farms in arid regions as well 

 as near dry washes and on foothills surrounding semides-ert valleys. 

 In the dry bottomlands of many shallow, narrow valleys in parts of 

 the West, rubber rabbitbrush now grows in dense stands where 

 giant wild-rye once grew abundantly but has now been killed out 

 by long-continued overgrazing. Probably rubber rabbitbrush has 

 similarly replaced other forage species that have been unable to 

 withstand disturbing factors to which they \vere exposed. 



Ordinarily under normal conditions the forage value of rubber 

 rabbitbrush is either nil or very low. From September to November 

 all classes of domestic livestock lightly graze the flowertops and 

 occasionally eat meager quantities of the herbage and more tender 

 stems. This shrub is sometimes lightly browsed on the winter range 

 and a few reports indicate localized, moderate to heavy utilization, 

 but this probably represents an overstocked condition. 



Rubber rabbitbrush has a very stout woody base from which arise 

 numerous flexible branches. A multitude of slender, erect, semi- 

 herbaceous stems are produced annually. The shreddy-barked basal 

 stalks are hairless, but the branches, and ordinarily the young stems 

 and the leaves, are coated with a more or less dense, matted, woolly 

 covering of fine, short white hairs which give a characteristic whitish 

 color to the bushes. These are often infiltrated with a resinous gum, 

 making the plant sticky and giving a characteristic odor. On some 

 plants the younger stems and the leaves are less densely hairy while 

 occasional older branches lose their hair and become pale or grayish 

 green. The hairy "seeds" (achenes) are slender, angled, and encir- 

 cled at the top by a brushlike row of numerous white, slender 

 bristles which serve to buoy the "seed" as it is disseminated by the 

 wind. 



1 Hall, H. M., and Goodspeed, T. H. A RUBBER PLANT SURVEY OF WESTERN NORTH 

 AMERICA. Calif. Univ. Pubs., Bot. 7 : [159]-278, illus. 1919. 



