Plant of the Week
Xylorhiza glabriuscula range map. USDA PLANTS Database.
Smooth Woody Aster (Xylorhiza glabriuscula). Photo by Charmaine Delmatier.
Smooth Woody Aster (Xylorhiza glabriuscula) habitat. Photo by Charmaine Delmatier.
Smooth Woody Aster (Xylorhiza glabriuscula)
By Charmaine Delmatier
Even though there seems to be one popular common name, smooth woody aster, this distinctive daisy-like subshrub has several synonyms (Aster glabriuscula, Aster glabriuscula var. parryi, Aster parryi, Aster xylorhiza, and Machaeranthera glabriuscula). It is a stout perennial forb/herb with a taproot and branched woody caudex. The ray florets are white, sometimes leaning toward purplish, and can have a slightly yellow center. They number 12 to 25 per involucre, and there can be 7 to 14 flowering heads per plant. When in bloom, it resembles a small ornamental shrub you might find in your yard. The white corollas can dominate the shrub almost appearing like a large snowball. Although isolated, smooth woody aster has been observed growing in large populations. Smooth woody aster populations are found in various dry habitats including sagebrush steppe and salt desert scrub.
A native to North America, its distribution is limited to Colorado, Montana, South Dakota, Utah, and Wyoming. It will flower usually around May and June, but can be as late as July, depending on local environmental conditions. The woody stems are branched with some hairs but mostly glabrous. The leaves are narrower between 2-8 mm wide, not clasping, and their margins are entire. It is easy to identify in the field, because it is not growing with many other flowering plants.
An interesting aspect of this unique member of the sunflower family is that you can smell its habitat and soil before walking up to individual plants. Usually found in open sites between 3,600 and 7,550 feet, it is often associated with selenious soils. Younger plants are especially high in selenium concentrations and when eaten can cause selenium intoxication. Sheep are the main browser and most susceptible to acute symptoms from selenium poisoning, such as muscle weakness and a drooping head. More severe symptoms include frothy and bloody discharge from the nose, stiffness, staggering while walking, and an elevation in both heart and respiratory rates. If untreated, death can occur within 3 to 4 days. There is not an effective treatment except abstaining from digesting younger plants. Selenium concentrations in smooth woody aster decrease as the flowering-heads mature. The modest stench from selenium deposits in the soil can be smelled well before you come across a population of smooth woody aster.
Conversely, its relative, the Mojave aster or desert aster (Xylorhiza tortifolia), is drank as a tea and a substitute for caffeine and coffee. Others have burned the roots over hot cinders as an insecticide to deter mosquitoes.