Figure 24. — A large stand of 

 Wyoming big sagebrush (A. 

 tridentata ssp. wyomingensis 

 growing near its type location^ 

 Daniel, Sublette Co., Wyoming. 

 Note size contrast to basin 

 big sagebrush of figure 25. 



Artemisia tripartita Rydb. (threetip sagebrush) 



Threetip sagebrush is a rounded, evergreen shrub up to 2 meters high. It may have 

 a simple, trunklike main stem or several branches arising from the base. The bark on 

 young branches is canescent, but becomes shredded and grayish, light brown to dark 

 brown or black on older stems. This species can layer, sometimes sprouts back after 

 a burn, and may sprout from the stump following herbicide treatments (Beetle 1960; 

 Pechanec and others 1965; Schlatterer 1973). 



Leaves of the vegetative branches are canescent, 0.5 to 4 cm long, and typically 

 deeply divided into 3 linear or narrowly linear-lanceolate lobes (fig. 12d), which in 

 turn may be 3-cleft. Some of the upper leaves are often entire. Crushed foliage 

 emits a pungent odor. 



Flower heads contain 3 to 11 disc flowers and are normally arranged into panicles. 

 Ray flowers are lacking. Each head is subtended by 8 to 12 canescent involucral bracts. 

 Achenes are resinous-granuliferous . Blooming occurs from July to September. Cleaned 

 seeds average 5,490 per gram (2,490,000 per pound). 



Hybridization. --Artemisia tripartita occurs in both diploid (2n = 18) and tetra- 

 ploid (2n = 36) forms (Ward 1953; McArthur and Pope, data on file at the Shrub Sciences 

 Laboratory, Prove, Utah) . Some evidence of natural hybridization involving this species 

 and other shrubby Artemisia has been found (Beetle 1960; Hanks and others 1973). 



Distribution and habitat . --Threetip sagebrush covers approximately 3,370,000 

 hectares (13,002 square miles) in the Northern Rocky Mountains and Great Basin States 

 from British Columbia south through Montana and Wyoming to Colorado and west to 

 Washington, Oregon, northern Nevada, and northern Utah at elevations between 900 to 

 2,750 meters (3,000 to 9,000 feet) (Beetle 1960). In some places, particularly in 

 Idaho, this species occurs between the lower, hot, dry sites dominated by Wyoming 

 big sagebrush and the higher, cooler sites dominated by mountain big sagebrush 

 (Schlatterer 1973) . 



(/se . --Threetip sagebrush is a vigorous seeder, but unfortunately some forms are 

 not particularly palatable. Beetle (1960) reported it was of low palatability for 

 both livestock and game, and Brunner (1972) observed that it was never grazed in 



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