Like Rodney Dangerfield, a common Bingham County shrub can claim it gets no respect. Although rabbitbrush is a widespread shrub, frequently occurring in sagebrush-dominated habitats throughout much of the west, it’s often ignored by hikers, photographers, biologists, and others interested in the West’s shrub-dominated habitats. Two species commonly occur throughout much of southeastern Idaho, rubber rabbitbrush (aka gray rabbitbrush) and yellow rabbitbrush (aka green rabbitbrush). Both are perennial shrubs and members of the Aster family.
Rubber rabbitbrush has several different subspecies. It’s characterized by whitish to green flexible stems, felt-like matted hairs, and narrow, thread-like grayish-green alternate leaves. Shrubs are rounded and generally two to five feet tall. Flower heads are made up of small, yellow, tubular flowers, arranged in dense, rounded or flat-topped clusters at the ends of branches. Flowers bloom from August to October as other plants are fading, providing vibrant color and a pollen source for insects in late summer. Shrubs reproduce by small, wind-dispersed seeds and can also sprout from the base.
Yellow rabbitbrush is similar in overall appearance and biology to rubber rabbitbrush. It is a low- to moderate-growing shrub reaching mature heights of a little over three feet. Stems can be smooth or somewhat hairy depending on variety, and covered with pale green to white-gray bark. Leaves are green, linear to oblong (less than 2.5 inches long), relatively narrow, and often appear twisted. Flower heads are 0.2 to 0.3 in long with glandular or hairy bracts (modified leaves). Individual flowers are yellow, fairly small, and produce a small, dry one-seeded fruit. There are five recognized varieties of yellow rabbitbrush which can be distinguished by leaf physical characteristics and distribution.
Rubber rabbitbrush can be a dominant or minor component in many plant communities, ranging from arid rangelands to montane openings. It thrives in poor conditions, and can tolerate coarse, alkaline soils. Dense stands are often found on degraded rangelands, along roadsides, and in abandoned agricultural fields because this shrub quickly invades disturbed areas.
Yellow rabbitbrush occurs in dry areas in sagebrush, ponderosa pine, lodgepole pine, and aspen belts at elevations between 2,600 and 11,000 feet. It is well adapted to drought and exhibits salt tolerance. Like rubber rabbitbrush, this species also increases rapidly on disturbed sites. It is a seral species in sagebrush communities and occupies disturbed areas after competing vegetation has been removed. This shrub persists in small numbers in naturally disturbed areas such as washes and talus slopes. Yellow rabbitbrush usually remains dominant for 15 years after disturbance, but then declines and is replaced by species such as big sagebrush.
Despite often being overlooked, rabbitbrush is a valuable native shrub. Native Americans reportedly used rabbitbrush for a yellow dye, a medicinal tea, and chewing gum. The forage value of rubber rabbitbrush varies. In some locations, it can be an important browse species for mule deer, pronghorn, and jackrabbits during fall and winter.
Rabbitbrush was tested as a source of high-quality rubber during World War II. In recent decades, there has been renewed interest in its potential for production of rubber, resins, and other chemicals. Compounds in rubber rabbitbrush are being evaluated for nematicides, anti-malarial properties, and insect repellents.
Yellow rabbitbrush is browsed by big game and livestock. It is considered desirable fall forage for cattle, sheep, horses, elk, and pronghorn, and spring forage for deer. Yellow rabbitbrush provides cover for sharp-tailed grouse, songbirds, and rodents. In southeastern Idaho, yellow rabbitbrush plants may be almost completely consumed by black-tailed jackrabbits during winter and early spring. It has been successfully used for revegetating depleted rangelands, strip mines, and roadsides.
So, the next time you are wandering through some of our shrub-dominated habitats don’t overlook these interesting and useful shrubs.