Purshia tridentata / antelope bitterbrush

Adjectives: clonal, drought tolerant, exposed, frost sensitive, interesting bits, native, shrub, winter botany

Also known as:  bitterbrush, antelope bush, buckbrush, quinine brush

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Bitterbrush is a very long-lived member of the Rosaceae (the rose family). If you stare at the flowers long enough, their “rose-iness” is clear, but you have to get over the fact that the leaves look very much like big sagebrush.

Bitterbrush is usually found along with sagebrush, and can be quite high on the mountains, especially on dry slopes, which it prefers. It is even adapted to desert life. Its drought tolerance is made possible by leaves with a thick cuticle and dense hairs, and by its long taproot. It also likes high limestone soils, another plus for living in the Valley. On the other hand, like sagebrush, it doesn’t tolerate being burned, especially in the spring, and especially if it is surrounded by cheatgrass (which, fortunately, hasn’t made it here yet).

There are several ways to distinguish (at the cell phone level) between bitterbrush and sagebrush. The first is to see them in spring. At the end of March (see the Gallery photo) bitter brush is just beginning to leaf out; sagebrush is evergreen so it is really easy to see the difference then. Bitterbrush also blooms in the spring (late May, early June) while sagebrush blooms in late summer.

Another way is to see the flowers: if you can actually see them, they aren’t sagebrush. The flowers are solitary (unlike sagebrush) on short branches, yellow with five petals and long stamens that extend well beyond the petals. Each stamen is topped with a large yellow anther.

Bitterbrush also has greener-looking leaves because of differences in the trichomes, and perhaps deeper notches at the ends of the leaves. And of course, bitterbrush lacks the characteristic aroma of sagebrush. Finally, I guess, yet another way is to look for deer and/or antelope (or moose) playing. Bitterbrush is an important browse for both.

Bitterbrush has highly branched prostrate stems which can root where they touch the ground… a process known as layering. It also grows well from seed. In drought and/or hot weather, the leaves can curl inward exposing their hairy undersides.

Interesting bits – bitterbrush is an important component of dry ecosystems such as the sagebrush slopes in the Valley as a browse, but also as a source of much needed nitrogen for the soil and other plants. It is one of relatively few species that can form a symbiosis with a nitrogen-fixing bacteria, Frankia. The bacteria form nodules on the bitterbrush roots in which atmospheric nitrogen gas is converted to forms useable by plants. Inevitably, some of this is released from the Purshia roots and fallen leaves to the soil and taken up by other species. As part of a broader effort to understand this type of N-fixation and the plants that do it, the genome of P. tridentata has been sequenced.