Artemisia tridentata

Description

Big sagebrush is a coarse, many-branched, pale-grey shrub with silvery-grey foliage and yellow flowers, typically 0.5–3 m tall. Its deep taproot, 1–4 m long, and shallow lateral roots allow it to draw water from both surface precipitation and the water table. Plants over a meter tall indicate arable land, as the species prefers deep, basic soils. Once past the seedling stage, sagebrush is long-lived and can exceed 100 years.

The leaves are wedge-shaped, 1–3 cm long and 0.3–1 cm broad, with three lobes at the wider outer tip, and are covered with fine silvery hairs. The plant flowers in late summer or early fall, producing small yellow flowers in long, loosely arranged tubular clusters. Fruits are seed-like with a small amount of surface hairs. Sagebrush can also reproduce via sprouts from underground rhizomes; seedlings require more moisture for germination than sprouts.

The essential oil contains about 40% l-camphor, 20% pinene, 7% cineole, 5% methacrolein, and 12% a-terpinene, d-camphor, and sesquiterpenoids.

Taxonomy

Botanists disagree on how to classify big sagebrush into subspecies. Some recognize six: basin, mountain, Wyoming, scabland, subalpine, and Parish's. The Wyoming type grows in drier steppe, with fewer than one shrub per square meter and sparse ground cover. Other classification schemes exist.

Ecology

Sagebrush provides food and habitat for animals such as sage grouse, pronghorn, gray vireo, pygmy rabbit, and mule deer, and is especially important to game animals in winter. Its long taproot draws water from deep soil, making some available to surrounding shallow-rooted plants. The terpenoid compounds in big sagebrush are thought to ward off herbivores; at high concentrations, these oils 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 from grazing triggers the release of volatile chemicals that signal nearby plants to increase repellent compounds, a communication that can occur up to 60 cm away. Major threats to sagebrush ecosystems include human settlements, conversion to agricultural land, invasive species, wildfires, and climate change. The invasive cheatgrass (Bromus tectorum), introduced accidentally in the 1890s, has radically altered the ecosystem by replacing native vegetation and creating a fire cycle too frequent for sagebrush to re-establish.

Sagebrush lacks fire tolerance and relies on wind-blown seeds from outside burned areas. Some tree species, such as Abies concolor (white fir), have also encroached on its habitat. This species hosts several insect-induced galls, including those from flies of the genus Eutreta and Oxyna aterrima.

Uses

The Cahuilla gathered large quantities of sagebrush seed and ground it into flour. The plant's active medicinal constituents include camphor, terpenoids, and tannins. Native Americans throughout the Intermountain West use it as a herbal medicine, most notably as a smudging herb, and for preventing infection in wounds, stopping internal bleeding, and treating headaches and colds. The Navajo use sagebrush vapors for headache treatment. The Okanagan and Colville people used it to smoke hides. Among the Zuni, an infusion of the leaves is applied externally for body aches, taken as a cold medicine, and placed in shoes to treat athlete's foot, fissures between toes, and as a foot deodorant.