U.S. D. A. Photo
Wyoming Big Sagebrush
Artemisia tripartita (Nutt.)
ssp. wyomingensis Beetle and Young
It is the most drought tolerant of the 3 major big
sagebrush subspecies . Plants are generally 18 to 30 inches tall, with rounded,
uneven crowns. The root system is deep and well developed, with many laterals
and one or more taproots. The majority of roots (about 35% of the total root
system) are in the upper 1 foot of soil. Some roots may penetrate as far as 6
feet. The main stem is
usually branched at or near ground level into 2 or more sub-stems. Wyoming big
sagebrush is technically an evergreen but is semi-deciduous in habit. It
develops 2 types of leaves: large ephemeral leaves and smaller, perennial leaves
produced from ephemeral leaf axes. The inflorescence is an open, many-flowered
spike. The fruit is a small, easily shattered achene. It
is a medium to small compact shrub with petite gray-green leaves that are
three-toothed at the tip. It makes a
striking silver accompaniment to traditional green landscapes.
Flowering begins in Aug. or Sept., and
fruits ripen in mid-Oct. to mid-Nov. Flowering continues until the
onset of cold weather. It is a long-lived species. In an undisturbed
Wyoming big sagebrush community in southern Wyoming, plants ranged from 26 to 57
years of age; average age was 42 years. Wyoming big sagebrush communities occur on sites with greater than 7 inches of annual precipitation.
It is most common on foothills, undulating
terraces, slopes, and plateaus, but also occurs in basins and valley bottoms;
occurring on frigid, mesic, and xeric soils of silty, clayey, skeletal, and
mixed textures. In riparian zones, it usually develop s on gravelly
outwashes and high floodplains Found in Idaho at 2,500 to 6,500 feet on the
Snake River Plains and on the Fort Hall Indian Reservation in
Value for Wildlife:
Wyoming big sagebrush is preferred browse for wild ungulates, and Wyoming big sagebrush communities are important winter ranges for big game. On the Idaho National Engineering Laboratory, for example, the shrub comprised 90% of the diet of pronghorn from fall through spring. Wyoming big sagebrush is a crucial food item of sage grouse, and Wyoming big sagebrush communities are critical habitat for the birds.
Wyoming big sagebrush reproduces from seed; it does not sprout or layer. Pollination is mostly by out crossing, but plants can also self pollinate. Shrubs produce large quantities of small seeds beginning at 3 to 4 years of age. Goodwin estimated that a moderate-sized plant produces about 350,000 seeds in a season, and a large one produces over a million. Big sagebrush seed is disseminated mostly by wind, with some seed spread by animals and water. The seed floats, so seedlings may establish along watercourses . Most seed shatters within a week of maturation and travels less than 100 feet (30 m) from the parent plant. Some viable seed is retained on the parent and disseminates slowly over the winter . Establishment occurs mostly from the seed bank. Wyoming big sagebrush seed stored in the warehouse has retained viability for at least 6 years ; viability in the field is unknown. On burns, Wyoming big sagebrush that escape fire are an important seed source . If the seed bank is destroyed over a large area by repeated fires or other means, Wyoming big sagebrush eventually seeds in from adjacent areas, but such a strategy may take several decades.
Return to main page