Montana Field Guide

PLANTS: Aromatic shrubs of 10–40 cm tall (Lesica 2012) that sprout from roots (FNA 2006). Stems are gray-green to brown, brittle, and glabrate (FNA 2006). Plants are glabrate to tomentose, and sometimes with obscure resin dots beneath the tomentum (FNA 2006; Lesica 2012).

LEAVES: Aromatic, gray-green, wedge-shaped (cuneate), 5–25 mm long, and tipped with 3 lobes (FNA 2006). Upper leaves are densely hairy (not sticky) (FNA 2006). Leaves on flowering stems are deciduous while those on non-flowering stems are persistent (FNA 2006).

INFLORESCENCE: Spiciform with linear bracts (Lesica 2012).

In Montana we have subspecies arbuscula and longiloba which are profiled separately in the Plant Field Guide.

Artemisia arbuscula is a well-developed shrub that is relatively short (less than 40 cm tall) (Lesica 2012). Leaves are tipped with 3 lobes and lack resin dots or at least they are inconspicuous (Lesica 2012). Bracts that subtend the inflorescence are linear and tomentose (Lesica 2012).

Sagebrush steppe in montane elevations (Lesica 2012).

Sagebrush habitats are diverse, unique, and imperiled, supporting a substantial number of endemic plants and animals (Dumroese et al. 2015). The rich flora and invertebrate fauna is vital for Greater Sage-Grouse broods (Dumroese et al. 2015).

Sagebrush in general is adapted to climates with cold winters where most precipitation falls in the winter (Meyer 2008). Sagebrush relies on wind for pollination and seed dispersal (Meyer 2008). Limited data suggests that Artemisia arbuscula seeds are adapted to germinate under snowcover and emerge early in spring as the snow melts. Differences in dormancy and germination requirements in woody sagebrushes appear to correspond to habitat, with populations in snowier, montane areas requiring light exposure or a longer chilling time. This may prevent premature germination in these moister environments; populations in warmer, drier areas tend to lack these dormancy traits (Meyer 2008).

The relative palatability of woody sagebrushes can be predicted by soaking the leaves in water and testing for fluorescence under ultraviolet light. Stronger fluorescence indicates higher levels of coumarin and increased palatability. Based on this test, Artemisia arbuscula is the most patable of the woody Artemisia species (Rosentreter 2005). Greater Sage-Grouse feed substantially on the leaves; during the winter, they feed solely on this and other sagebrushes (Dumroese et al. 2015). Pronghorn, elk, deer, and sheep are also among the animals that browse this species (Tilley and St. John 2012). Rabbits and ground squirrels use the leaves and seeds (Johnson 1993).

Flowers: Four to eight yellow disk flowers are surrounded by a bell-shaped involucre which is three to five millimeters high. The involucral bracts are green and woolly, like the leaves (Lesica et al. 2012).

Fruit: The fruits are tiny achenes, averaging 1,810,000 per kilogram (Meyer 2008). They are resinous and less than one millimeter long (Lesica et al. 2012). The achene’s outer layer (pericarp) has mucilaginous nerves that may help it stick to the soil while the embryonic plant’s root penetrates (Meyer 2008).

As with all Artemisia species, flowers are wind pollinated. Hybrids have been reported between Artemisia arbuscula and Artemisia tripartita ssp. tripartita, A. tridentata ssp. tridentata, and A. tridentata ssp. wyomingensis (Steinberg 2002).

In habitats dominated by Artemisia arbuscula, fire is rare because of limited fuels. When fire does occur, typically in moister sites or in years with lush plant growth, A. arbuscula is often killed (Steinberg 2002). Unlike Artemisia cana it does not re-sprout after fire, though branches that are not killed can regrow (Steinberg 2002). In good conditions, A. arbuscula can recover from fire in two to five years, regenerating from wind-blown seeds (Steinberg 2002). Grazing can reduce the incidence of fire as native grass fuel sources decrease. In turn, this can lead to invasion by juniper (Steinberg 2002). Conversely, in some cases grazing can contribute to invasion by annual grasses such as Bromus tectorum, increasing the chances of fire (Steinberg 2002).
Typical seed longevity for sagebrush species in a warehouse is two to three years (Meyer 2008). For restoration, Artemisia arbuscula can be seeded in fall or winter (Meyer 2008). The tiny seeds should be placed no deeper than 1.5 millimeters (Tilley and St. John 2012). In marginal conditions where winter snowfall is insubstantial or is blown away, small snow-fences can help establishment, mimicking the role of mature sagebrush (Meyer 2008).