Artemisia tridentata / mountain big sagebrush

Adjectives: clonal, drought tolerant, exposed, fragrant, highly visible, interesting bits, native, nutrient poor soils, rocky, shrub, silvery leaves, striking, widespread, winter botany

Also known as: big sagebrush,  sagebrush

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Sagebrush is an aromatic evergreen shrub. In late summer and early fall, it develops tall stalks of loosely arranged tubular flower clusters. The flowers are technically yellow, but they not really visible. There are hundreds of clusters on a single stem, and each has between 2 and 10 flowers. Each of these, when pollinated by wind or by selfing, yields a single minuscule seed. Given the thousands – or even hundreds of thousands – of flowers per plant, that is enough. Of course, like other wind pollinated species, sagebrush tends to be poorly thought of by folks with pollen allergies.

In addition to reproduction by seed, sagebrush can send up sprouts from underground rhizomes. As these can receive nutrients and water from the mother plant, they are less susceptible to drought than young seedlings.

Sagebrush is an iconic plant throughout much of the west and southwest, including in the Valley. It is the dominant and defining plant for its ecosystem. If you think that that grey, dead-looking bush might be sagebrush, go rub its leaves. The aroma is describable, if you know what camphor smells like, but unmistakable even if you don’t. While you’re at it, notice the three tooth-like lobes at the ends of the leaves. These are why it is A. tridentata.

Sagebrush is extremely well adapted to its exposed, arid or semiarid and cold environment. It has heavy, reflective pubescence on leaves and young stems. This, along with the vertical orientation of the leaves, reduces the light and heat reaching the critical cells inside the leaves. It also has a deep taproot that accesses the deep water table, reducing the impact of surface drought. Wide-spreading shallow roots are good for collecting water following short rains.

Because of its drought tolerance, big sagebrush is found especially on south facing or fully exposed slopes. In the various east-west canyons off the Valley, it is found primarily on the north side (exposed to the mid-day sun), up high enough on the slopes or ridges that it is away from the moisture of the stream beds and shadows of trees. In some places, however, it extends down-slope to the willows along streams.

Interesting bits – There are several subspecies of big sagebrush, each dominating its favored environment and each performing much less well if planted in a different one. In Idaho, mountain big sagebrush (Artemisia tridentata ssp. vaseyana) dominates. Basin big sagebrush (Artemisia tridentata ssp. tridentata) may have been here at one time, but its presence signals deep, fertile soils and more moisture. As a result, much of it was pulled up by settlers wanting to plant something else.

Big sagebrush provides important grazing for sage grouse, antelope and mule deer, pygmy rabbits and grey vireos. Nutritionally, it is quite good, but the secondary chemicals responsible for the lovely smell are antinutrients. Thus, they limit the species that can digest it.

Finally, if you were to be, or decide to be, an environmental physiologist, and were wandering around sagebrush lands in very early spring, or even in mid winter, you would question how it can survive with leaves exposed to full sun and more (the light being reflected off the snow), with no water supply (the soil being frozen). Leaves can’t do photosynthesis without losing water, and this environmental combination is perfect for inducing photoinhibition – the damage to chloroplasts by excess light. So if you figure out the answer, let me know.