Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young
Prepared by: Sheryl Harrison
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Latin name meaning: The species name, tridentata, refers to the 3-toothed leaves. Family: Asteraceae. Common names: Wyoming big sagebrush. Similar species: Artemisia tridentata ssp. tridentata (basin big sagebrush) and ssp. vaseyana (mountain big sagebrush). Mountain big sagebrush grows at higher elevations over 1,150 m (6,29,36), basin big sagebrush grows at intermediate elevations, on sites more mesic than those supporting Wyoming big sagebrush, and is over 2 m tall (6,29). Wyoming big sagebrush grows at the lowest elevations of the three subspecies, and sheds 60-65% of its foliage under severe drought (6,29). Another similar species is Artemisia tripartita (threetip sagebrush). Threetip sagebrush is smaller, has leaves that are deeply cleft into three narrow, linear divisions and has 5-8 disk flowers (36). Associated species: Agropyron spicatum, Balsamorhiza sagitatta, Stipa lettermanis Poa fendleriana, Achillea lanulosa, Penstemon spp. and Aster spp (38). |
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Stem: The woody stem of this species is branched, over 7 cm in diameter and shredding on older branches, but densely hairy on young twigs (36,48). Leaves: Leaves of Wyoming big sagebrush are mostly 3-toothed, but can be entire near the apex of the plant, 1-3 cm long, densely hairy on top and bottom surfaces, and persistent through the winter (36,48). The leaves contain oils giving them a distinct odor when crushed (48). Roots: Wyoming big sagebrush has a long taproot and shorter fibrous roots. It absorbs moisture from deep within the soil and move it up, releasing it in the upper part of the soil profile at night (11). The roots can penetrate deep enough to break protective barriers at hazardous waste sites (8). Inflorescence/flowers: The inflorescence of Wyoming big sagebrush is an elongate, loose panicle (36,48). The flowers are in composite heads of 3-5 disk flowers, and are small and yellow (36). Fruit: The seeds of Wyoming big sagebrush are sparsely hairy (36). |
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Photosynthetic pathway: Wyoming big sagebrush is a C3 shrub. Phenology: Twig elongation for Wyoming big sagebrush begins in mid-April and lasts until late June (13). Flowers of this species appear in late August (13,36,48), but flower bud development can last from mid-June until early September (13). Wyoming big sagebrush forms and sheds seeds between October and December (13,48). Seeds remain viable in the soil for one year (48). Seeds may be transported by wind, water or animals, but most seeds remain near parent plants (18). Average germination for Wyoming big sagebrush over a 3 year study was 54% (20) at temperatures between 2 and 30C (14,19,32). Seeds require light for germination, but if the pericarp is removed or short chill treatments are given to the seeds, light requirements decrease (33). Wyoming big sagebrush reaches maximum growth 2 weeks sooner than the other two subspecies, enhancing its ability to survive on xeric sites (7) Distribution: Wyoming big sagebrush grows in the Intermountain west, east of the Continental Divide in Montana, Wyoming and parts of Colorado. It is scattered in Mixed Grass Prairie in Northern Great Plains and east to the Black Hills. Wyoming big sagebrush is common in the grasslands of southern British Columbia. Habitat: Of the three subspecies, Wyoming big sagebrush is most adapted to poor, infertile sites. Wyoming big sagebrush is intolerant of alkaline soils (36). It grows on dry, gravelly, shallow sites ranging from 725 m to 2,500 m (4,31). Wyoming big sagebrush grows on the warm desert fringe to forests and meadows (33) and can survive on sites receiving less than 282 mm of precipitation annually (16). Ground Cover/LAI/Height: Wyoming big sagebrush is usually less than 1 m tall (48). Small mammals and birds seek this species for cover (15) more than other species growing in association with it (40). Sage grouse choose Wyoming big sagebrush for cover 71% of the time when nesting (42). Succession: Wyoming big sagebrush is a late successional species, occurring in climax communities. Indicator value: An abundance of Wyoming big sagebrush, indicates an overgrazed site and/or a site that has not burned for a long time. It is also an indicator of a soil with low fertiliy. Competition: Wyoming big sagebrush is competitive and reduces perennial grass production (23,48). |
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Grazing: Of the three subspecies of big sagebrush, Wyoming big sagebrush is the most palatable. Preference ranges from poor to fair for cattle and horses (46) and fair to good for sheep (15). Overgrazing by domestic livestock allows Wyoming big sagebrush to increase. Wildlife: Wyoming big sagebrush is commonly eaten by elk and mule deer (49). It also makes up 76% of pronghorn diets in the spring (35). Ground squirrel burrows increase the amount of spring recharge of soil moisture, which enhances productivity of Wyoming big sagebrush (30). Burning: Wyoming big sagebrush is killed by burning (3,9,26,34,39,45). Wyoming big sagebrush will regenerate quicker on small burned sites than on large ones because seeds can move in from surrounding plants (27). Smoke from burning Wyoming big sagebrush enhances leaf production and elongation of native grasses (5). Restoration: Several years may be required to re-establish this species because it grows on infertile, low producing sites (12,46). Special management: Wyoming big sagebrush is the most common woody species in western U.S. rangelands, occupying over 60 million ha (46). Rest from grazing has decreased its cover by 29% (46). Burning is the most effective method for removing Wyoming big sagebrush, followed by chemical and mechanical methods (34,46,48). Burning or spraying this species can increase production of associated species in subsequent years (28,41,46,). Applying 2,4-D at 1.3 kg/ha or 2,4,5-T at 2.8 kg/ha kills Wyoming big sagebrush (28,41). Other: Native peoples from the southern Interior of British Columbia used the leaves and branches of this species to make teas for colds and used the leaves as a fumigant (36). The bark was woven into mats, bags, and clothing (36). The aromatic leaves of Wyoming big sagebrush inhibit the oviposition of Mexican bean weevils (Zabrotes subfasciatus) (46). |
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