Currently there are six subspecies of Artemisia tridentata recognized by the National Plant Data Center: basin (ssp. tridentata), Wyoming (ssp. wyomingensis Beetle & Young), mountain (ssp. vaseyana [Rydb.] Beetle), subalpine (ssp. spiciformis [Ousterhout] Kartesz & Gandhi), xeric (ssp. xericensis Winward ex R. Rosentreter & R. Kelsey) and Parish’s (ssp. parishii [Gray] Hall & Clements). Each is highly variable with multiple ecotypes, but can generally be separated using a number of morphological, geographical and topographical characters.
All chromosome number information was obtained from McArthur and Sanderson (1999) as updated in McArthur (2005). Appendix 1 contains a general summary of characteristics useful to separate subspecies. See McArthur and Stevens (2004) for a detailed review of the characters for the subspecies occurring in the Intermountain West.
Figure 2. Leafy stem of basin big sagebrush. Photo courtesy of the PLANTS database.
Basin big sagebrush usually occurs at the lowest elevational range of the species, being most abundant in the valley bottoms to mountain foothills. Plants typically have a single main trunk and may grow to a height of 4 m (13 ft) under proper conditions, making basin the largest subspecies. Basin big sagebrush plants are generally uneven-topped with loosely branching flowering stems distributed throughout the crown (see figure 1). Floral heads typically contain 3 to 6 small flowers per head. Leaves of the vegetative stems are narrowly cuneate averaging 2 cm (0.8 in) or more and can be as long as 5 cm (2 in) being many times longer than wide (see figure 2). Ultraviolet visible coumarins in leaf extracts are minimal; leaf UV color is none to light blue in water and a rusty red-brown color in alcohol. 2n = 18 or sometimes 36.
Figure 3. Wyoming big sagebrush.
Derek Tilley, USDA NRCS Idaho PMC
Wyoming big sagebrush overlaps in range and elevation with basin big sagebrush. Plants are considerably smaller than those of basin big sagebrush, usually less than 0.9 m (3 ft) tall, and have main stems branching from the ground (see figure 3). Flowering stems are not as widely branching as those of basin, but otherwise closely resemble that subspecies. Leaves are typically shorter, from 1 to 1.5 cm (0.4 to 0.6 in) long, and flabelliform. UV extract color in water is none to light blue and rusty in alcohol. 2n = 36.
The vegetative stems of mountain big sagebrush create a characteristic even topped crown with the panicles rising distinctly and relatively uniformly above the foliage (see figure 3). Plants are normally smaller than those of basin big sagebrush, averaging about 0.9 m (3 ft) tall. Inflorescences are narrow and spicate bearing flower heads containing 4 to 8 flowers per head. Leaves are characteristically wider than those of basin or Wyoming big sagebrush. In extracts, ultraviolet visible coumarins are abundant. Leaf extracts fluoresce blue in water and blue-cream in alcohol. 2n = 18 or sometimes 36.
Figure 4. Even topped mountain big sagebrush.
Derek Tilley, USDA NRCS Idaho PMC
Originally considered a xeric form of mountain big sagebrush, xeric big sagebrush shares similarities with both basin and mountain big sagebrush and may be the result of hybridization between the two subspecies. Xeric big sagebrush plants are large and have an uneven topped crown like those of basin big sagebrush, but in leaf UV color and cytological characters it resembles mountain big sagebrush. Ultraviolet visible coumarins are blue in water, blue-cream in alcohol. 2n = 36.
A new variation of big sagebrush being recognized by some is Bonneville big sagebrush. This as yet undescribed taxon may represent hybridization between Wyoming and mountain big sagebrush. It is reported to have the general growth form of Wyoming plants but bears the leaves and fluorescing characteristics of the mountain subspecies. It has been reported from the bench areas of Lake Bonneville and other ancient lakes of the Intermountain West in Utah and Nevada. Reports of Bonneville big sagebrush have also come from western Wyoming and western Colorado. Of particular importance is this sagebrush’s reported high palatability to wild ungulates and sage grouse.
Subalpine, or spicate big sagebrush, is believed to be a stabilized hybrid between mountain big sagebrush and silver sagebrush (Artemisia cana Pursh ssp. viscidula [Osterhout] Beetle). Plants are similar to those of mountain big sagebrush except that leaves and floral heads are larger, the floral heads having 10 to 18 flowers per head. Ultraviolet visible coumarins in leaf extracts fluoresce blue in water and blue-cream in alcohol. 2n = 18 or 36.
Parish’s big sagebrush is an uncommon taxon restricted to dry, sandy soils in the hills of southern California. It is nearest in appearance and relationship to basin big sagebrush, but differs from basin in having drooping flowering branches and the achenes are hairy. 2n = 36.
One additional taxon that should be mentioned is Lahontan sagebrush (Artemisia arbuscula ssp. longicaulis Winward and McArthur). It is thought to be a stable hybrid between low sagebrush (A. arbuscula) and Wyoming big sagebrush. It bears the flowers of low sagebrush but has the vegetative characteristics of its big sagebrush parent. This subspecies forms dominant communities in northwestern Nevada and adjacent portions of California and Oregon in shallow or clayey soils above and around the shoreline of the Pleistocene Lake Lahontan.
The following key should provide some assistance in separating the subspecies of big sagebrush.
1. plants larger, usually >0.9 m (3 ft) tall, with a
single main trunk; crown uneven with floral stems
2. achenes hairy; floral stems drooping; plants
endemic to sandy soils in southern
2. achenes glabrous; floral stems erect; plants
widely distributed throughout western U.S,
including southern California
3. plants occurring in valley bottoms and low
foothills, occupying deep fertile soils; leaves
narrowly cuneate, 2-5 cm (0.8-2.0 in) long,
UV leaf color in water=none, in alcohol=red
to brown ……...................…...ssp. tridentata
3. UV in water=blue, in alcohol=blue-cream;
plants restricted to well-drained basaltic soils in western Idaho….........ssp. xericensis
1. plants smaller, averaging 0.9 m (3 ft) or less, with
trunks branching at or near ground level; crowns
4. crowns uneven-topped, plants of low
valleys and foothills;
5. UV color in water=none, in alcohol=rust
5. UV color in water=blue, in alcohol=blue-
4. crowns even-topped, floral stems rising
uniformly above the vegetative stems; plants of
6. flowers 4 to 8; leaf tips lobed
6. flowers 10 to 18; leaf tips often pointed
Additional taxonomic information can be found in the Flora of North America, Volume 19 (FNA Editorial Committee 2006) and the Intermountain Flora, Volume 5 (Cronquist et al. 1994).
General: Although big sagebrush plants generally have a similar growth form, the species does have considerable morphological variation with several subspecies and ecotypes. Big sagebrush are evergreen shrubs ranging in size from less than 0.6 m (2 ft) tall to as large as 4 m (13 ft) tall. Branches are spreading, arising from numerous main stems in the lower growing subspecies or from one main trunk in the larger forms. Leaves are blue-gray to blue-green in color due to dense gray hairs. They are typically cuneate (wedge-shaped, triangular and gradually tapering to the base) or flabelliform (bell shaped) depending on subspecies, and have three lobes at the apex on the majority of the persistent foliage. Leaves vary in length from 0.5 to 5 cm (0.2 to 2.0 in), and can be 0.2 to 2.0 cm (0.08 to 0.8 in) wide. Leaves are spirally arranged with internodes short in young vegetative stems making the leaves very dense. Panicles overtop plants of mountain and spicate big sagebrush, or can grow throughout the crown in basin and Wyoming big sagebrush. Floral heads contain from three to 18 perfect (both male and female parts present) flowers per head. Achenes are typically glabrous but are hairy in the California endemic Parish’s big sagebrush. Big sagebrush plants are very aromatic with the smell being described as bitter pungent to pleasant, the odor varying by subspecies. Ploidy levels often differ among subspecies and may differ among populations.
A. tridentata ssp. parishii = Parish’s big sagebrush
A. tridentata ssp. spiciformis = subalpine or spicate big sagebrush
A. tridentata ssp. tridentata = basin big sagebrush
A. tridentata ssp. vaseyana = mountain big sagebrush
A. tridentata ssp. wyomingensis = Wyoming big sagebrush
A. tridentata ssp. xericensis = xeric or foothills big sagebrush
Regularity: Regularly occurring
Regularity: Regularly occurring
Global Range: This species has a very wide range extending from British Columbia south to Baja, California and Arizona. Its range extends eastward to the New Mexico, Colorado, and the Dakotas (FNA, 2006).
Fossil records and records from early pioneers indicate that sagebrush was widespread and existed in nearly the same general distribution for the past several thousand years as it does in the present day. Densities of sagebrush communities, however, have been reduced historically due to range management practices. Big sagebrush presently covers a vast ecological range from British Columbia to Baja California eastward to the Dakotas. Mahalovich and McArthur (2004) provide distribution as well as seed and plant transfer guidelines for Artemisia subgenus Tridentatae. For current distribution for each subspecies, please consult the Plant Profile page for this species on the PLANTS Web site.
Artemesia tridentata is much larger than most species in the genus. It's leaves are persistent and have lobes less than 1/3 the length of the leaf blade versus lobes greater than 1/3 the length on A. tripartita (FNA 2006). Unlike those of A. rothrockii, the leaves of A. tridentata are not sticky-resinous and are persistent.
Colorado Plateau Shrublands Habitat
This taxon can be found in the Colorado Plateau shrublands, as one of its North American ecoregions of occurrence. The Plateau is an elevated, northward-tilted saucer landform, characterized by its high elevation and arid to semi-arid climate. Known for the Grand Canyon, it exhibits dramatic topographic relief through the erosive action of high-gradient, swift-flowing rivers that have downcut and incised the plateau. Approximately 90 percent of the plateau is drained by the Colorado River and its tributaries, notably the lower catchment of the Green River.
A pinyon-juniper zone is extensive, dominated by a pygmy forest of Pinyon pine (Pinus edulis) and several species of juniper (Juniperus spp). Between the trees the ground is sparsely covered by grama, other grasses, herbs, and various shrubs, such as Big sagebrush (Artemisia tridentata) and Alder-leaf cercocarpus (Cercocarpus montanus).
A montane zone extends over large areas on the high plateaus and mountains, but is much smaller than the pinyon-juniper zone. The montane vegetation varies considerably, from Ponderosa pine in the south to Lodgepole pine and Aspen further north. Northern Arizona contains four distinct Douglas-fir habitat types. The lowest zone has arid grasslands but with many bare areas, as well as xeric shrubs and sagebrush. Several species of cacti and yucca are common at low elevations in the south.
Numerous mammalian species are found within the Colorado Plateau shrublands ecoregion, including the Black-tailed prairie dog (Cynomys ludovicianus); Long-eared chipmunk (Tamias quadrimaculatus); Utah prairie dog (Cynomys parvidens EN); Yellow-bellied marmot (Marmota flaviventris); and the Uinta chipmunk (Tamias umbrinus), a burrowing omnivore.
A large number of birds are seen in the ecoregion, with representative taxa: Chestnut-collared longspur (Calcarius ornatus NT); Greater sage grouse (Centrocercus urophasianus NT); Northern pygmy owl (Glaucidium gnoma); Cactus wren (Campylorhynchus brunneicapillus).
There are various snakes occurring within the Colorado Plateau, including: Black-necked garter snake (Thamnophis cyrtopsis), usually found in riparian zones; Plains Blackhead snake (Tantilla nigriceps); Black-tailed rattlesnake (Crotalus molossus), who seeks inactivity refuge in rock crevices, animal burrows and even woodrat houses. Other reptiles found here include the Common checkered whiptail (Cnemidophorus tesselatus).
There are only a limited number of anuran taxa on the Colorado Plateau; in fact, the comprehensive occcurrence list for the ecoregion is: Red-spotted toad (Anaxyrus punctatus); Canyon treefrog (Hyla arenicolor); Woodhouse's toad (Anaxyrus woodhousii); Couch's spadefoot toad (Scaphiopus couchii); Northern leopard frog (Lithobates pipiens); Plains spadefoot toad (Spea bombifrons); and Southwestern toad (Anaxyrus microscaphus). The Tiger salamander (Ambystoma tigrinum) is the sole salamander found on the Colorado Plateau shrublands.
The Colorado River fish fauna display distinctive adaptive radiations. The Humpback chub (Gila cypha), for example, is a highly specialized minnow that lives in the upper Colorado. It adapted to the water’s fast current and its extremes of temperature and flow rate. Dams and water diversion, however, have created a series of placid, stillwater lakes and side streams, and the Humpback chub may not be able to adapt to these altered conditions. The species, along with other native Colorado River fishes including the Bonytail (Gila elegans), Squawfish (Ptychocheilus lucius), and the Flannelmouth sucker (Catostomus latipinnis), may not survive much further in time.
Sierra Juarez and San Pedro Martir pine-oak forests Habitat
This taxon can be found in the Sierra Juarez and San Pedro Martir pine-oak forests. The ecoregion is located in two mountain ranges in the state of Baja California, Mexico: the Sierra de Juarez and the Sierra de San Pedro Martir. Both mountain ranges belong to the physiographical province of Baja California, and constitute the northernmost elevated peaks of the Baja Peninsula. The mountainous range that descends into a large portion of Baja California becomes more abrupt at Juarez and San Pedro Martir; the eastern slope is steeper than the western. Altitudes range between 1100-2800 meters. The granitic mountains of Juarez and San Pedro Martir have young rocky soils and are poorly developed, shallow, and low in organic matter.
Dominant trees in the ecoregion are: Pinus quadrifolia, P. jeffreyi, P. contorta, P. lambertiana, Abies concolor, and Libocedrus decurren. The herbaceous stratum is formed by Bromus sp. and Artemisia tridentata. Epiphytes and fungi are abundant throughout the forests.
Characteristic mammals of the ecoregion include: Ornate shrew (Sorex ornatus), Puma (Puma concolor), Fringed Myotis bat (Myotis thysanodes), California chipmunk (Tamias obscurus), Bobcat (Lynx rufus), Coyote (Canis latrans), San Joaquin kit fox (Vulpes macrotis) and Bighorn sheep (Ovis canadensis).
Numerous birds are present in the ecoregion, including the rare Bald eagle (Haliaeetus leucocephalus), California condor (Gymnogyps californianus), Pinyon jay (Gymnohinus cyanocephalus), and White-breasted nuthatch (Sitta carolinensis).
A number of different reptilian taxa are found in these oak-pine forests; representative reptiles here are: the Banded rock lizard (Petrosaurus mearnsi); Common checkered whiptail (Cnemidophorus tesselatus), who is found in sparsely vegetated areas; Coast horned lizard (Phrynosoma coronatum), often found in locales of sandy soil, where individuals may burrow to escape surface heat; Night desert lizard (Xantusia vigilis), who is often found among bases of yucca, agaves and cacti; and the Baja California spiny lizard (Sceloporus zosteromus).
The Pacific chorus frog (Pseudacris regilla) is an anuran found within the Sierra Juarez and San Pedro Martir pine-oak forests as one of its western North America ecoregions of occurrence. The only other amphibian in the ecoregion is the Western toad (Anaxyrus boreas).
Comments: This plant dominates hundreds of square km of sandy valley floors and plains above approximately 5000 feet elevation (Rhode, 2002). It is drought tolerant but cannot stand excessive sub-moisture. It grows on moderately shallow to deep, well-drained, sandy to silt loam soils of neutral to slightly alkaline reaction. It occurs on practically all range except meadows and at high elevations (USDA, 2010).
The big sagebrush complex is adapted to a wide range of precipitation zones and soil conditions. Plants are well adapted to the arid plains, valleys, foothills and mountains of the West where annual precipitation ranges from as little as 200 to as much as 750 or more mm (8 to 30 in). It is often found growing in loamy to sandy loam soils, but plants are found on all 12 soil textural classes in five soil orders: Alfisols, Aridisols, Entisols, Inceptisols and Mollisols. Tolerance to alkalinity or acidity varies by subspecies. In general big sagebrush will grow in soils with a pH of 5.9 to 10.0 and with organic matter content of 0.62 to 4.14 percent.
Basin big sagebrush is commonly found at low to mid elevations from 600 to 2,100 m (1,900 to 6,900 ft) in valleys and mountain foothills, occupying sites with deep fertile loamy to sandy soil, 0.9 m (3 ft) or deeper. It is often the dominant shrub species of the plant community, but is also found in association with juniper, piñon pine and rabbitbrush communities. Basin big sagebrush has a deep penetrating root system that allows it to occupy deeper soils in areas receiving little precipitation. Plants are often found growing in valleys, plains, alluvial fans and in seasonal or perennial stream channels. Basin big sagebrush prefers soils which are non-alkaline, non-saline and non-calcareous. The deep root system does not allow plants to grow in soils with a soil depth limiting hardpan or caliche layer. Depending on soil infiltration and water storage capacity, plants will grow in areas receiving less than 200 to more than 400 mm (8 to 16 in) annual precipitation. This subspecies also does not tolerate soils saturated for more than a few weeks in a season.
Wyoming big sagebrush grows at low to intermediate elevations between basin and mountain big sagebrush, but also commonly overlaps in range with the other two subspecies. When found in proximity with basin big sagebrush, Wyoming sagebrush will occupy the shallower, better-drained soils. Like basin big sagebrush, Wyoming is typically found in large stands covering many acres. Plants are also found in juniper, rabbitbrush, bitterbrush and mountain mahogany communities. At lower precipitation areas it is sometimes intermixed with shadscale and other Atriplex species. Wyoming big sagebrush commonly occurs from 800 to 2,200 m (2600 to 7,200 ft) in elevation. Wyoming big sagebrush is the most drought tolerant of the big sagebrush subspecies and is commonly found growing on low valley slopes and foothills receiving between 200 and 300 mm (8 to 12 in) annual precipitation. It occupies loamy soils with high clay content and a depth of 25 to 75 cm (10 to 30 in). Soils may be quite rocky or gravelly, but in these cases plants will be smaller. Wyoming big sagebrush will be found growing in soils underlain by a caliche or silica layer if the available soil is deep enough. Plants are typically found in soils with a low water holding capacity where excess water may run off into channels more suitable to basin big sagebrush.
Mountain big sagebrush grows in mountain and mountain foothill plant communities such as rabbitbrush, piñon pine, juniper, mountain shrub, aspen, Douglas fir, ponderosa pine and spruce-fir habitats from 800 to 3,100 m (2,600 to 10,000 ft). Plants prefer moderately deep to deep, well-drained soils providing summer moisture. Mountain big sagebrush occurs at higher elevations and in higher annual precipitation zones than either Wyoming big sagebrush or basin big sagebrush. Soils are typically 45 to 90 centimeters (18 to 36 in) deep or more, and are most often loamy to gravelly but can contain greater amounts of clay. Plants commonly grow in areas receiving over 350 mm (14 in) annual precipitation, but may be found in lower elevations and precipitation zones under certain conditions such as snow drift accumulation areas and shaded north facing slopes.
Xeric big sagebrush is limited to basaltic and granitic soils of western and west central Idaho and is often associated with bluebunch wheatgrass. Plants grow in the foothills from 800 to 1,500 meters (2,600 to 4,900 ft). Precipitation ranges from 300 to 400 mm (12 to 16 in) annually.
Spicate big sagebrush grows at high elevation ridge lines and snow accumulation areas from 2,000 to 3,300 m (6,500 to 10,800 ft) in annual precipitation zones of over 750 mm (30 in). It is normally found near Douglas fir, spruce-fir, and aspen communities.
Figure 5. Adaptation of Intermountain big sagebrush subspecies based on elevational and moisture gradients (Mahalovich and McArthur, 2004).
Parish’s big sagebrush is adapted to the dry sandy soils of California’s Inner South Coast Ranges, South Coast, Western Transverse Ranges, White and Inyo Mountains and the desert mountains of the Mojave Desert.
Seed of big sagebrush are best adapted to germinate in habitats with ecological conditions approximating those of the seed collection site. Seed source and subspecies should always be seriously considered prior to seeding. It may be necessary to use seed from more than one subspecies in a given revegetation project to ensure adequate establishment in all habitats.
Seed should be sown in the late fall or early winter and allowed to naturally stratify. It should be noted that big sagebrush seed has special seed storage requirements (See “Seed and Plant Production” section). If stored in conditions with relative humidity above 30 percent, seeds lose vigor and germinability after two or three years. To ensure a greater chance of establishment success, check the viability of seed lots before planting.
Seed should be planted into a firm, weed-free seedbed at a depth of no more than 1/8 inch. Seed covered too deeply with soil will generally fail to establish. Best results come from surface broadcast seed that has been pressed into the soil to provide for good seed-soil contact. Seed can also be broadcast directly onto snow with good results. Pressing broadcast seed into the soil surface with a land imprinter has provided very good establishment success. Land imprinters create good contact between the seed and soil as well as provide microhabitats that optimize temperature and water requirements. Broadcast seeding has also yielded good results when followed by a cultipacker or drag chain.
Drill seeding can be successful, but strict attention must be paid to seeding depth. Optimal drilling depth is 0 to 1/8 inch.
Sagebrush seed lots range in purity from approximately 8 to 30 percent or greater pure seed. Seed lots with high purity levels (20 percent or greater) can be difficult to seed due to limitations of the seeding equipment. Because sagebrush seed is very small and is metered through seeding equipment with difficulty, seed can be diluted with rice hulls or another inert carrier to improve flow.
Post-fire aerial seeding of big sagebrush has been done with limited success. Studies suggest that best results come from aerial seeding followed by land imprinting, cultipacking or chaining, or after allowing native perennial grasses to establish for a season following fire. It is believed that native grasses would suppress exotic annual grass species while allowing the establishment of sagebrush. Further study of this option is indicated.
Big sagebrush is not recommended for pure seedings. Seed should be a small component of a seed mix. Drill seeding 0.025 lbs PLS per acre (approximately 1 viable seed/ft²) provides approximately 400 plants per acre for optimal wildlife habitat. For broadcast seeding increase to 0.05 to 0.075 lbs PLS (approximately 2-3 viable seeds/ft²). With adequate soil moisture seedlings develop quickly and compete well with other shrubs and most herbaceous plants. However, to enhance establishment, sagebrush should not be sown in the same drill row with more aggressive forbs and grasses.
Sagebrush seedlings require sufficient soil moisture to germinate and survive. Young plants do not do well in open, unprotected locations. Best establishment results occur in sites where soil moisture is at or near field capacity, or in areas where snow accumulates. Existing shrubs, downed trees and litter can create microhabitats which also provide very good germination conditions.
Containerized stock or bareroot seedlings can also be used with high establishment success (50% or greater). This method, however, is quite costly, and is rarely used except in small critical area plantings. Plants can be taken from nursery stock or field harvested wildings. Wildings should be collected and transplanted during dormancy in fall or very early spring when soil moisture conditions are best. For best cost efficiency, “mother plants” should be placed in key locations throughout the revegetation site to allow for natural seed dispersal and recruitment over time.
Known Pests: Puccinia tanaceti, a rust fungus, causes the disease "black stem rust" (Welch and Nelson 1995).
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: > 300
Comments: In North Dakota, it is locally common only in Bowman to McKenzie Cos. (Stevens (1963).
The Sage Grouse utilizes Artemesia tridentata as nest cover, shelter, and a food source. Because A. tridentata is evergreen, it is one of their most important food sources outside the growing season. Other species also depend on this species as a food source: elk, mule deer, pronghorn, and pygmy rabbits (Tirmenstein 1999).
Sagebrush species are associated with mycorrhizal fungus in the genus Glomus which may be required for the establishment of seedlings (Tirmenstein 1999).
Life History and Behavior
Persistence: PERENNIAL, Long-lived, EVERGREEN
Molecular Biology and Genetics
Barcode data: Artemisia tridentata
Statistics of barcoding coverage: Artemisia tridentata
Public Records: 1
Specimens with Barcodes: 2
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Reasons: This species, and its various subspecies, has a very wide range and extends approximately from the Sierra Nevada in the west to the plains of the Rocky Mountains in the east. It is one of the most widespread shrubs in North America and appears stable, or perhaps increasing, throughout its range.
Environmental Specificity: Moderate. Generalist or community with some key requirements scarce.
Comments: It is a somewhat drought tolerant plant and grows on a variety of soil types on arid plains, valleys, foothills, and mountains.
Consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).
Global Short Term Trend: Relatively stable to increase of 25%
Global Long Term Trend: Unknown
Degree of Threat: Unknown
Comments: Sagebrush is not fire-tolerant and relies on wind-blown seeds from outside the burned area for re-establishment. Big sagebrush is readily killed when aboveground plant parts are charred by fire. If sagebrush foliage is exposed to temperatures above 195 degrees Fahrenheit (90C) for longer than 30 seconds, the plant dies. Among the three major subspecies of big sagebrush, basin big sagebrush is considered intermediate in flammability. Mountain big sagebrush is most flammable, and Wyoming big sagebrush is least flammable. Since the advent of effective fire control and intensive livestock grazing (reducing ground fuel and understory competition), regeneration and establishment of western juniper have expanded into suitable sites previously dominated by Artemisia tridentata. Western juniper (Juniperus occidentalis) is also intolerant of fire and historically, spread was restricted by natural fires (Tirmenstein, 1999). This expansion of young stands of western juniper is common in Oregon, Idaho, and northeastern California (Burns and Honkala, 1990). However, suppression of fire results in hotter and longer burning fires that are typically followed by the spread of the invasive cheat grass (Bromus tectorum). Especially in Washington state, habitat loss and fragmentation pose the greatest threat to the species (Gamon, pers. comm., September 2011).
Pests and potential problems
Perhaps the greatest danger to sagebrush stands comes from fire. Big sagebrush plants have no fire resistance and many acres are destroyed annually because of increased fire frequency resulting from infestations of exotic annual weeds such as cheatgrass and medusahead.
Another minor cause of sagebrush mortality is winter injury. This occurs when temperatures drop quickly below freezing before plants have entered dormancy, or when a warm spell promotes winter growth followed by a return to typical winter temperatures. Extended periods of winter and summer drought (normally more than 2 years) can also cause dehydration and death.
Big sagebrush is occasionally susceptible to limited outbreaks of the sagebrush defoliator moth, or webworm, (Aroga websteri). Although the moths can cause extensive damage, they too are subject to insect predators, and it is rare that entire stands will be lost.
Additionally, there are a number of other microbial and fungal pathogens known to attack big sagebrush. Although these may inflict serious damage locally, they have not been viewed as a great threat to sagebrush populations.
Cultivars, improved and selected materials (and area of origin)
‘Hobble Creek’ mountain big sagebrush was released by the Utah Agricultural Experiment Station, Utah State University and the USDA Forest Service Rocky Mountain Research Station in 1987. Seed was originally collected in 1968 by A. Perry Plummer at the Hobble Creek drainage east of Springville, UT. ‘Hobble Creek’ was chosen for its high vegetative production and for its high palatability to mule deer and wintering domestic sheep. It is adapted to sites with deep, well-drained soils receiving more than 350 mm (14 in) of annual precipitation and having a growing season of 90 days or longer. Soils should be no finer than a clay loam, containing 40% or less clay and have a pH between 6.6 and 8.6. Breeder seed is maintained at a breeder block at the USDA Forest Service Rocky Mountain Research Station, Shrub Sciences Laboratory, Provo, UT.
‘Gordon Creek’ Wyoming big sagebrush was originally collected near Helper, Carbon County, UT. It was released in 1992 by the USDA Forest Service Rocky Mountain Research Station to fill the need for a low precipitation ecotype of big sagebrush to improve winter diets of mule deer and sage grouse and for rangeland restoration. Gordon Creek was chosen for its high growth rate, nutrient levels and mule deer preference. It is widely adapted to dry regions of the west receiving 250 or more mm (10 in) mean annual precipitation. It prefers deep to shallow, well-drained soils with up to 55% clay content with a pH of 6.6 to 8.8.
Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
The vast majority of big sagebrush seed used in revegetation is wildland collected material. Seed collection occurs in late fall to early winter (early October through the end of December) depending on the subspecies. Collections are commonly made by hand stripping, beating or clipping seed heads into containers or by using a reel type harvester. Seed can be cleaned with a hammermill, debearder, air-screen or gravity table with varying results. Most sagebrush seed lots used for rangeland seeding are only cleaned to a purity of 15 to 20 percent due to the small nature of the seeds (achenes). This practice requires less time for cleaning and also allows for easier seed flow and metering in seeding equipment. Pure seed yields approximately 1.7 to 2.5 million seeds per pound. The NRCS Plant Materials Center in Bridger, MT reported four hours collecting time and 5.5 hours cleaning yielded 200g (0.45 lb) cleaned material, or 21g (0.04 lb) per hour.
Sagebrush seed that has been dried to a minimum of 9 percent moisture content will remain viable for many years when stored under cool, dry conditions. Welch et al (1996) reported seed viabilities above 90% for seed stored at 10 ºC (50 ºF) and relative humidity (RH) of 20 percent after nine years of storage. Seed stored at higher RH levels are susceptible to germination or damage by insects or microorganisms.
Because sagebrush seed can readily be collected from wild stands, sagebrush is rarely grown in commercial production fields. However, in very droughty periods, very little sagebrush seed can be collected from wild stands. Increasing seed demands and decreasing sagebrush stands lost to weeds and fire are growing concerns. Recent studies suggest protecting wildland seed-producing stands for optimum harvesting. The greatest factor in seed production for sagebrush is protection against grazing animals. Surrounding plants with a wire fence has shown an increase in seed stalk number of as much as 3 to 5 times the amount of unprotected plants. Studies also show significantly higher seed yields from plants grown on reclaimed mine lands when compared with those on adjacent non-mined areas. The reason for this correlation is unclear, but it may be a result of increased available soil moisture due to lower competing plant frequencies on the mined lands.
Seed production varies greatly between years and between stands due to differences in climate, stand density and maturity, soil and genetics. It has been estimated that an average stand of big sagebrush could potentially produce 100 to 300 lbs PLS per acre annually. Seed production declines as plants and stands mature creating larger amounts of woody biomass. Greater seed yields can be achieved by thinning decadent stands to encourage new flower stalk production
For nursery plantings, pre-stratified seed can be planted in greenhouse conditions, or seed can be allowed to naturally stratify after being planted in containers outdoors. Keep soil medium slightly moist during germination. Greenhouse sprayers or misters are commonly used during daylight hours at a rate of 10 seconds every 15 minutes. Uniform germination occurs after two weeks of temperatures over 20º C (70º F). Seedlings are ready for field transplanting approximately 5 months after germination.
Historically, sagebrush communities have been poorly managed, mostly in attempts to reduce or eliminate sagebrush stands to increase forage production for livestock. Recently, however, the value of sagebrush to the western rangelands is being recognized, and practices are evolving to better manage healthy and productive sagebrush communities.
Contrary to long standing beliefs, studies show that complete sagebrush removal negatively affects biodiversity and has little long term affect on perennial grass production. Indeed, several studies indicate that forage production may actually decline when sagebrush is completely removed or controlled.
Overgrazing of the understory decreases plant biodiversity, especially the forb component of the plant community and increases the density of weeds. Annual weeds, such as cheatgrass (Bromus tectorum L.) and medusahead (Taeniatherum caput-medusae [L.] Nevski) often out-compete young sagebrush seedlings and create undesirable monocultures. Annual weed infestations also increase the frequency of wildfires which result in eliminating sagebrush stands therefore not allowing stand re-establishment.
Despite the many valuable benefits of sagebrush to rangelands, there may be cases when it is desirable to thin and rejuvenate sagebrush stands. In these instances it is not necessary to remove the entire stand, and control treatments in mosaic patterns are recommended. Several methods exist for partial removal of the shrubby over story.
Herbicide use is an effective means of thinning sagebrush stands. Contact your local agricultural extension specialist or county weed specialist to determine what works best in your area and how to use it safely.
Probably the simplest and most cost effective means of stand reduction is through prescribed burning. If there is sufficient fuel, a burn can completely eliminate a sagebrush community. For this reason niche burning is recommended when possible. In situations where cheatgrass is a dominant part of the understory, burning should take place when ripe cheatgrass seeds are still on the plants and will be consumed in the fire.
Methods of mechanical removal for sagebrush include anchor chaining, pipe harrowing, land imprinting offset disking and brush beating with brush hogs or mowers. Of these, chaining and land imprinting are the least expensive and do an excellent job of reducing sagebrush stands while still leaving enough plants for diversity and browsing. Brush beating does a good job, but it is expensive. Disking and harrowing also do a good job of shrub removal, but are more expensive and more destructive to under-story plant populations.
Relevance to Humans and Ecosystems
Comments: Some Native Americans used the bark of big sagebrush to make ropes and baskets (Tirmenstein 1999).
Forage/Wildlife: Big sagebrush is perhaps the most important shrub on western rangelands. Evergreen leaves and abundant seed production provide an excellent winter food source to numerous species of large mammals including mule deer, black-tailed deer, white-tailed deer, elk, pronghorn antelope, bighorn sheep and jack rabbits. Nearly 100 bird species depend on sagebrush ecosystems for their habitat needs. Additionally, there are several animal species having an obligate relationship with big sagebrush including sage grouse, sharp tailed grouse, pygmy rabbits, sage thrashers, sage sparrows and Brewer’s sparrow. Sagebrush also provide habitat and food for hosts of invertebrates which in turn support birds, reptiles and small mammals. In addition to the numerous species of animals that depend on sagebrush for food and cover, there are several plant species having close relationships with sagebrush as well.
Sagebrush plants maintain high levels of most nutrients including crude protein (see table 1). This high forage value makes it especially useful for wildlife, and in some areas livestock, winter grazing. Separate studies indicated that sagebrush made up 78% of the annual diet for antelope in Wyoming and 59% of the winter diet of deer and elk near Gardiner, Montana. Sagebrush also makes up close to 100% of the winter diet of sage grouse and over 60% of their total annual diet. Use of sagebrush by livestock is limited and variable.
Animal preference of sagebrush varies with subspecies, populations and even individual plants due to chemical variation found in the foliage. Deer and elk tend to prefer mountain big sagebrush followed by Wyoming big sagebrush and finally basin big sagebrush. Although many range managers believe that deer and other large mammals prefer to browse shrubby members of the Rosaceae such as mountain mahogany (Cercocarpus), bitterbrush (Purshia) and cliffrose (Cowania) over big sagebrush, studies show sagebrush significantly more readily browsed.
Sagebrush’s value as thermal or security cover is also very high for wildlife. This includes nesting cover and escape cover for sage grouse, sharp tailed grouse, pheasants, chukar and other upland birds.
Table 1. Nutritive values as percent dry matter and percent in-vitro dry matter digestibility (IVDMD).
(Adapted from Welch, 2005)
Revegetation/reclamation: Because of its wide range of adaptation and ease of establishment, big sagebrush can be a very important species for use in revegetation efforts. Seedlings are able to compete with grasses and forbs as well as other shrubs allowing it to be used as a component of a wide range of seed mixes. Seedlings are very easy to establish when planted correctly (see “Establishment” section) and can be drill seeded or broadcast with near equal levels of success. Because sagebrush plants spread readily by seed, it can be seeded at relatively low rates and allowed to spread by natural recruitment.
Big sagebrush plants provide many additional benefits to the plant community. The dense canopy protects understory herbaceous plants from grazing. Healthy sagebrush communities provide a multi- tiered ecosystem with high levels of biodiversity. Big sagebrush plants also have a two-part root system with a deep tap root and a shallow, diffuse root system. Numerous studies have shown sagebrush plants create “hydraulic lift” where deep soil moisture is brought to near the soil surface by the tap root system during the day and then released into the upper soil at night. This water is then available to the diffuse root system of big sagebrush as well as to the roots of other understory plants. Sagebrush plants also increase water retention by trapping and holding windblown snow.
Big sagebrush subspecies are often useful indicators of soil characteristics. Generally, a subspecies indicates the soils at a site, thus proper identification of big sagebrush at a subspecific level can provide useful information on soils and ecological site characteristics. In some areas, however, such as those with glacial deposits, a separation based on soil characteristics is considerably more complex.
Artemisia tridentata, commonly called "big sagebrush" or "sagebrush", is an aromatic shrub from the family Asteraceae, which grows in arid and semi-arid conditions, throughout a range of cold desert, steppe, and mountain habitats in the Intermountain West of North America. The vernacular name "sagebrush" is also used for several related members of the genus Artemisia, such as California Sagebrush (Artemisia californica).
Big Sagebrush and other Artemisia species are the dominant plants across large portions of the Great Basin, covering some 422,000 square miles in 11 western U.S. states & Canadian provinces. It is the state flower of Nevada. Sagebrush provides food and habitat for a variety of species, such as sage grouse, pronghorn antelope, gray vireo, pygmy rabbit, and mule deer.
- A. tridentata subsp. tridentata ("basin big sagebrush")
- A. tridentata subsp. vaseyana ("mountain big sagebrush")
- A. tridentata subsp. wyomingensis ("Wyoming big sagebrush") -- Found in the drier portions of the sagebrush steppe. Shrub density is generally less than 1 plant/m2, with little herbaceous cover surrounding the shrub.
- A. tridentata subsp. xericensis ("scabland big sagebrush")
- A. tridentata subsp. spiciformis ("subalpine big sagebrush")
- A. tridentata subsp. parishii ("Parish's big sagebrush")
Sagebrush is a coarse, many-branched, pale-grey shrub with yellow flowers and silvery-grey foliage, which is generally 0.5–3 m tall. A deep taproot 1–4 m in length, coupled with laterally spreading roots near the surface, allows sagebrush to gather water from both surface precipitation and the water table several meters beneath. Big sagebrush that is over a meter tall is an indicator of arable land, because it prefers deep, basic soils. Sagebrush is generally long-lived once it makes it past the seedling stage, and can reach ages of over 100 years.
Sagebrush has a strong pungent fragrance (especially when wet) due to the presence of camphor, terpenoids and other volatile oils. The taste is bitter and, together with the odor, serves to discourage browsing by many herbivores. It is an evergreen shrub, keeping some of its leaves year-round (although it loses many of them in the late summer). The leaves—attached to the branches at the axillary nodes—are wedge-shaped, 1–3 cm long and 0.3–1 cm broad, with the wider outer tips divided into three lobes (hence the scientific name tridentata). The leaves are covered with fine silvery hairs.
Sagebrush flowers in the late summer or early fall. The small yellow flowers are in long, loosely-arranged tubular clusters. The fruits are seed-like, and have a small amount of hairs on the surface. The Cahuilla used to gather large quantities of sagebrush seed, and grind it to make flour.
Big Sagebrush can also reproduce through sprouts, which shoot up from the underground rhizome. The sprouts are an extension of the parental plant while seedlings are completely individualistic to any other plant. Among these two strategies, the seedlings need more moisture for germination and early survival. This is due to the sprouts being connected to already healthy and associated plants while the new seedlings will start anew.
Artemisia tridentata grows in arid and semi-arid conditions, throughout the Intermountain West of North America. Sagebrush is not a desert plant, but rather a resident of the steppe, in areas that receive 18–40 centimeters (7.1–15.7 in) of annual precipitation. Big sagebrush and other Artemisia species are the dominant plants across large portions of the Great Basin, covering some 422,000 square miles (1,090,000 km2) in 11 western U.S. states and Canadian provinces. Sagebrush provides food and habitat for a variety of animal species, such as sage grouse, pronghorn, gray vireo, pygmy rabbit, and mule deer. Sagebrush also creates habitat for many species of grasses and herbs. Besides providing shade and shelter from the wind, the long taproot of sagebrush draws water up from deep in the soil, some of which becomes available to these surrounding shallow-rooted plants.
The terpenoid compounds in big sagebrush are thought to ward off herbivores. These oils, at high concentrations, are toxic to the symbiotic bacteria in the rumen of some ruminants like deer and cattle. Pronghorn are the only large herbivore to browse sagebrush extensively. Damage to sagebrush plants caused by grazing herbivores results in the release of volatile chemicals, which are used to signal a warning to nearby plants, so that they can increase the production of repellent chemical compounds. This plant-to-plant communication can take place at distances of up to 60 cm.
Several major threats exist to sage brush ecosystems, including human settlements, conversion to agricultural land, livestock grazing, invasive plant species, wildfires, and climate change. The cattle industry burns large areas of sagebrush habitat to make way for grazing animals. Due to large periods of time where sagebrush was the primary shrub, many species have become adapted to this habitat. The burning of the shrubs leads to habitat loss of many species and can be very detrimental to the ecosystem as a whole. Furthermore, the destruction of native grasses and forbs by grazing and fire creates conditions where invasive plants colonize the area. The invasive species which has destroyed the largest amount of sagebrush habitat is cheatgrass (Bromus tectorum). Since its accidental introduction in the 1890s, cheatgrass has radically altered the native shrub ecosystem by replacing indigenous vegetation, and by creating a fire cycle that is too frequent to allow sagebrush to re-establish itself. Sagebrush is not fire-tolerant and relies on wind-blown seeds from outside the burned area for re-establishment. Some tree species have also been encroaching on big sagebrush habitat. For example, in the Warner Mountains in California white fir (Abies concolor) has been out-competing big sagebrush.
Big sagebrush was used as an herbal medicine by Native Americans throughout the Intermountain West of North America—especially for preventing infection in wounds, stopping internal bleeding, and treating headaches and colds. Chemically, the active medicinal constituents include camphor, terpenoids, and tannins.
Among the Zuni people, an infusion of the leaves is used externally for body aches. The infusion is also taken as a cold medicine. It is also placed in shoes to treat athlete's foot, fissures between toes, and as a foot deodorant.
The plant's oils are toxic to the liver and digestive system of humans if taken internally, so care must be taken during any form of internal use. Generally, toxic symptoms will subside 24–48 hours after ingesting the plant.
- Barbour, Michael G. & Billings, William D. (2000). North American Terrestrial Vegetation. Cambridge University Press. p. 259. ISBN 9780521559867.
- Barbour, Michael G. et al. (2007). Terrestrial Vegetation of California. University of California Press. p. 599. ISBN 9780520249554.
- Brayshaw, T.C. (1996). "Artemisia tridenta Nutall. (Big Sagebrush)". Trees and Shrubs of British Columbia. University of British Columbia Press. p. 337. ISBN 9780774805643.
- Mozingo, Hugh N. (1987). Shrubs Of The Great Basin: A Natural History. University of Nevada Press. p. 271. ISBN 9780874171129.
- Baldwin, Bruce G. (2002). The Jepson Desert Manual: Vascular Plants of Southeastern California. University of California Press. p. 117. ISBN 9780520227750.
- Ferris, Roxana A. & Abrams, LeRoy (1960). "Artemisia tridentata Nutt. Sagebrush". Illustrated Flora of the Pacific States, Vol. IV: Bignonias to Sunflowers. Stanford University Press. p. 412. ISBN 9780804700061.
- Stuart, John D. & Sawyer, John O. (2001). "Big Sagebrush (Artemisia tridentata)". Trees and Shrubs of California. University of California Press. p. 169. ISBN 9780520221093.
- Clarke, Charlotte B. (1978). "Big Sagebrush". Edible and Useful Plants of California. University of California Press. p. 134. ISBN 9780520032675.
- Kershaw, Linda (2001). "Big sagebrush". Rare Vascular Plants of Alberta. University of Alberta. p. 25. ISBN 9780888643193.
- Raven, Peter H. (1996). Native Shrubs of Southern California. University of California Press. p. 54. ISBN 9780520010505.
- Tilford, Gregory L. (1997). Edible and Medicinal Plants of the West. Mountain Press Publishing. p. 208. ISBN 9780878423590.
- Jaeger, Edmund C. (1940). Desert Wild Flowers. Stanford University Press. p. 302. ISBN 9780804703659.
- Smith, Stanley D. et al. (1997). Physiological Ecology of North American Desert Plants. Springer. p. 107. ISBN 9783540531135.
- Mozingo, Hugh N. (1987). Shrubs Of The Great Basin: A Natural History. University of Nevada Press. p. 270. ISBN 9780874171129.
- Müller-Schwarze, Dietland (2006). Chemical Ecology of Vertebrates. Cambridge University Press. p. 310. ISBN 9780521363778.
- Smith, Genny (2000). Sierra East: Edge of the Great Basin. University of California Press. p. 168. ISBN 9780520086890.
- Barbour, Michael G. et al. (2007). Terrestrial Vegetation of California. University of California Press. p. 593. ISBN 9780520249554.
- Cresser, Malcolm S. & Smith, Keith A. (2003). Soil and Environmental Analysis: Modern Instrumental Techniques. CRC Press. p. 364. ISBN 9780824756949.
- Nagy, JG and RP Tengerdy. 1968. Antibacterial action of essential oils of Artemisia as an ecological factor: II. Antibacterial action of the volatile oils of Artemisia tridentata (big sagebrush) on bacteria from the rumen of mule deer" Applied and Environmental Microbiology 16(3) 441-444.
- Rogosic, J. et al. (2011). "Importance of plants with medicinal properties in herbivore diets". In Casasús, I. & Rosati, Andrea. Animal Farming and Environmental Interactions in the Mediterranean Region. Wageningen Academic Pub. pp. 47–48. ISBN 9789086861842.
- Lentz, David L. (2000). Imperfect Balance: Landscape Transformations in the Precolumbian Americas. Columbia University Press. p. 49. ISBN 9780231111560.
- Holopainen, Jarmo K. & Blande, James D. (2012). "Molecular Plant Volatile Communication". In López-Larrea, Carlos. Sensing in Nature. Springer. p. 20. ISBN 9781461417033.
- Knick, Steven T. & Connelly, John (2011). Greater Sage-Grouse: Ecology and Conservation of a Landscape Species and Its Habitats. University of California Press. p. 145. ISBN 9780520267114.
- Shepherd, Jay F. et al.. "Landscape Fragmentation and Non-Breeding Greater Sage-Grouse". In Sandercock, Brett K. et al.. Ecology, Conservation, and Management of Grouse. University of California Press. p. 78.
- Wambolt, C.L.; Walhof, Frisina (March 2001). "Recovery of big sagebrush communities after burning in south-western Montana". Journal of Environmental Management 61 (3): 243–252. doi:10.1006/jema.2000.0411.
- Radosevich, Steven R. et al. (1997). Weed Ecology: Implications for Management. John Wiley & Sons. pp. 29–30. ISBN 9780471116066.
- Radosevich, Steven R. et al. (2007). Ecology of Weeds and Invasive Plants: Relationship to Agriculture and Natural Resource Management. John Wiley & Sons. pp. 26–29. ISBN 9780471767794.
- This is in contrast to many of the other plants which share its habitat, such as Rabbitbrush, Ephedra and bunchgrasses, which can root-sprout after a fire.
- Boersma, P.D. & Van Buren, Amy N. (2006). Invasive Species in the Pacific Northwest. University of Washington Press. p. 36. ISBN 9780295985961.
- Vale, Thomas (1975). "Invasion of big sagebrush (Artemisia tridentata) by white fir (Abies concolor) on the southeastern slopes of the Warner Mountains, California". Western North American Naturalist 35 (3).
- Edible and Medicinal Plants of the West, Gregory L. Tilford, ISBN 0-87842-359-1[page needed]
- Kay, Margarita (1996). Healing with Plants. University of Arizona Press. pp. 106–107. ISBN 9780186516465.
- Pennacchio, Marcelo et al. (2010). Uses and Abuses of Plant-Derived Smoke: Its Ethnobotany As Hallucinogen, Perfume, Incense, and Medicine. Oxford University Press. p. 48. ISBN 9780195370010.
- Camazine, Scott and Robert A. Bye 1980 A Study Of The Medical Ethnobotany Of The Zuni Indians of New Mexico" Journal of Ethnopharmacology 2:365-388 (p. 374)
- Shakhnoza, Azimova S. et al. (2012). Lipids, Lipophilic Components and Essential Oils from Plant Sources. Springer. p. 844. ISBN 9780857293237.
- Aanderud, Zachary T. et al. (September 2008). "Shrub-interspace dynamics alter relationships between microbial community composition and belowground ecosystem characteristics". Soil Biology and Biochemistry 40 (9): 2206–2216. doi:10.1016/j.soilbio.2008.04.008. ISSN 0038-0717.
- Taylor, Ronald J. (1992). Sagebrush Country: A Wildflower Sanctuary. Mountain Press Publishing. ISBN 9780878422807.
|Wikimedia Commons has media related to Artemisia tridentata.|
- NCRS: USDA Plants Profile: Artemisia tridentata
- Germplasm Resources Information Network-GRIN: Artemisia tridentata
- GIS Database for Sage Grouse and Shrubsteppe Management in the Intermountain West
- The Sagebrush Sea
Names and Taxonomy
Comments: This species has undergone considerable taxonomic revision in the past century and circumscription of subspecies remains a topic of considerable controversy. Workers in the field should be aware of the morphologic variation within the subspecies across the range of the species (i.e., approximately from the Sierra Nevada in the west to the plains of the Rocky Mountains in the east). Because rangeland managers and conservationists can often identify local morphologic and chemical races based on grazing or habitat preferences of wildlife and domestic animals, some impetus exists to further subdivide the subspecies at the varietal level. This treatment of the species complex remains conservative in light of the need for further study (Flora of North America Editorial Committee, 2006).
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