Subspecies .--Artemisia oana ssp. cana (silver sagebrush) is an erect, rounded, 

 freely branched shrub up to 1.5 meters tall. It layers whenever conditions are suitable. 

 This subspecies may spread rapidly, particularly after burning, by rootsprouting and by 

 rhizomes (Beetle 1960). Leaves of the vegetative branches are linear-oblanceolate, 

 entire or rarely with 1 or 2 irregular teeth or lobes, 1 to 10 mm wide, 2 to 8 cm long, 

 and are densely silky-canescent (fig. 9) . Crushed foliage emits a pungent turpentine 

 odor (Ward 1953; Beetle 1960). Flower heads are usually arranged into dense, leafy pan- 

 icles and may contain from 5 to 20 disc flowers. Blooming occurs during September, and 

 the seeds ripen during October and November. Putative natural hybrids between subspecies 

 oana and both basin and mountain big sagebrush have been found (Ward 1953; Beetle 1960). 

 Subspecies oana has a more eastern distribution than subspecies visoidula. It occurs 

 from southern Canada southward, but mostly east of the Continental Divide, through 

 Montana, the Dakotas, Wyoming, western Nebraska, and northern Colorado. Its type 

 locality is "on the bluffs, Missouri River" (Beetle 1960). 



Artemisia oana ssp. visoidula (mountain silver sagebrush) is an erect shrub that 

 readily layers. It usually is not more than 1 meter tall. Leaves on the vegetative 

 branches are 1 to 5 mm wide, up to 7 cm long (fig. 9), and are often crowded in dark- 

 green clusters. The leaves typically are simple and entire but occasionally are 

 variously toothed or lobed. This subspecies varies in appearance, but is always darker 

 green than mountain big sagebrush with which it is often growing (Beetle 1960) . Moun- 

 tain silver sagebrush is distinguished from subspecies oana by its smaller, darker green 

 leaves, its lower stature, and more western distribution. Flower heads are arranged 

 into dense, short raceme or spikelike inflorescences 1 to 3 cm long. Each head contains 

 from 4 to 15 disc flowers. Flowers bloom during August and September. Seed matures 

 during October and November. Putative natural hybrids involving this subspecies and A. 

 tripartita ssp. tripartita, A. tridentata ssp. vaseyana, and A. tridentata ssp. triden- 

 tata have been found (Beetle 1960; Hanks and others 1973). Beetle (1960) believes 

 Artemisia argitosa may have arisen from a cross between A. oana ssp. visoidula and A. 

 longiloba, and that A, tridentata ssp. vaseyana f. spioiformis may have developed from 

 a cross between A. oana ssp. visoidula and /I. tridentata ssp. vaseyana. Mountain silver 

 sagebrush occurs in mountainous regions around 2,100 meters (6,900 feet) and above. 

 It is usually found along streamsides and in areas of heavy, lingering snowpack from 

 the southwest corner of Montana, south along the Continental Divide to New Mexico, and 

 west to Arizona, Nevada, Utah, and Idaho. Mountain silver sagebrush type locality is 

 Routt County, Colorado (Beetle 1960). A similar subspecies, A. oana ssp. bolanderi 

 (Bolander silver sagebrush), occurs in extreme western Nevada and in California and 

 Oregon. It is more canescent than ssp. visoidula and grows on poorer drained, usually 

 more alkaline soils than does visoidula (Beetle 1960). 



Artemisia filifolia Torr. (sand or oldman sagebrush) 



Sand sagebrush is a round, freely branching shrub up to 1.5 meters tall (fig. II). 

 Young branches are covered with a canescent pubescence while the older stems are covered 

 by a dark-gray or blackish bark. 



The filiform silvery-white canescent leaves are 5 to 8 cm long, less than 0.5 mm 

 wide, entire or ternately divided into filiform divisions, and are often fascicled 

 (fig. 12a). 



Numerous, nodding heads containing 2 or 3 fertile, pistillate ray flowers and 1 to 

 6 perfect but sterile disc flowers are arranged into leafy, narrow panicles. Each head 

 is subtended b\- 5 to 9 canescent involucral bracts. Both the receptacle and achenes are 

 glabrous. Flowers bloom during August and September. Seed ripens from October to De- 

 cember. Cleaned seed averages 6,910 per gram (3,135,000 per pound). 



Hybridization . --Sand sagebrush has a chromosome number of 2n = 18 (McArthur and 

 Pope 1977). It is a distinctive taxon that is not known to hybridize with other 

 Artemisias. Fxotypic selection and subseijucnt hybridization and development might be 

 possible. Hall and Clements (1923) suggested that birdfoot sagebrush {A. pedatifida) 



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