22 October 2010

Spotlight On...Rubber Rabbitbrush

Rubber Rabbitbrush
Chrysothamnus nauseosus
Asteraceae (Sunflower Family)
Quick ID:  
In general, Rabbitbrush appears similar to Big Sagebrush--a scrubby shrub with grayish-tinged, woolly leaves.  Like sagebrush, it's found in dry, open plains or disturbed sites, and grows about 1 to 6 feet high.  The leaves are linear and alternate on flexible stems.  The yellow flowers bloom late (August-October), blanketing the plains and slopes with the type of brilliant display most flora exhausted months ago.  Being in the Asteraceae family, each flower is actually a loose cluster of mini-blooms known as "disc flowers", like the ones in the eye of a sunflower or daisy.  The "ray flowers" that we know as petals in other Asteraceae species are absent in Rabbitbrush.  
Found up to 10,000', from Canada to Mexico, east of the Pacific mountain system and stretching to the Great Plains.  Look for it growing near dryland bunchgrasses and shrubs like Big Sagebrush (Artemesia tridentata), Basin Wildrye (Leymus cinereus), Mountain Mahogany (Cercocarpus ledifolius) and Bluebunch Wheatgrass (Pseudoregenaria spicata).
What's in a Name?
A quick note on taxonomy:
It's the most fickle sport among scientists, always in flux and impossible to keep up on.  It's not so easy to remember all this archaic Latin binomial nomenclature, and once you think you've got it down, a new taxonomical relationship is discovered or refuted, groups are shuffled around, and the 15 syllable name you've been proudly slipping into casual conversation and engraving onto your garden signs is now obsolete.  So if you're the type to stick with what you know and ignore all the newfangled monikers, I, for one, won't judge you.
That said, Rubber Rabbitbrush is technically known as "Ericameria nauseosa (Pallas ex Pursh) G.L. Nesom & Baird", but in my heart of hearts, it will always be Chrysothamnus.  Chryso- means gold, -thamnus a thicket.  The "nauseous" root in the specific epithet is in reference to the strong smell the plant gives off, rather than the idea that ingesting it will make you sick.  In fact, the plant's thick latex has been used for centuries as a sort of chewing gum (hence the "Rubber" part).  It provides shelter for and is eaten by rabbits and other small mammals.
In some southern parts of the country, Rabbitbrush is known almost exclusively as Chamisa, from the Spanish word for brush or kindling, and ultimately derived from the Latin chama (-->flamma-->"flame").        
The presence of Rabbitbrush, which often grows on very poor soils, and is considered a useful indicator that land is eroded or overgrazed.  It can be an important winter forage for antelope, mule deer and elk on depleted rangelands, but is sometimes reported to be toxic to livestock.
The plant has a few adaptations that allow it to thrive in arid, inhospitable places.  It's tolerant to a wide range of soil types, alkalinity, salinity, cold and drought.  The felt-like fuzz covering the stems (technically known as trichomes) acts as insulation and reduces water loss.  The light gray stems also reflect more heat than dark green leaves would, keeping the shrubs cool as a cuke in the harsh summer sun of the open prairie.
Historically, Rabbitbrush has been used to make yellow or green dye, and prepared as a tea to help coughs and colds.  The flexible twigs are good for baskets, and the seeds can be ground and used much like cornmeal.  
People have been looking for a way to use the natural latex found in the roots and inner bark to produce rubber since the 1930s, but haven't found a commercially viable way to extract it.  There is currently an investigation underway by the University of Nevada, looking at the potential of Rabbitbrush as a multi-use industrial crop for biomaterial and bioenergy applications.  Here's the interesting project summary.

Wild Gardening:  Plants need about 4' of space, and take about 4 years to mature.  They tend to produce about a million branches, generally arising from a common point and not overtaking neighbor plants.  Overwatering or fertilizing can produce leggy, sprawling plants.  New plants sprout up from the roots and can be divided, and the seeds germinate easily.
Being a late bloomer, Rabbitbrush fills an important niche both as an ornamental perennial and a fall pollen source for bees, flies and butterflies.  To see this plant in late fall, spilling over with brilliant color and buzzing with hundreds of hungry and deprived insects, is really incredible.  It tolerates fussing-over, but seems to delight in neglect: no extra water, no soil amendments, no pruning or deadheading.  The soft, pale branches complement the muted palette of a xeric landscape perfectly, and provide a safe haven for nesting birds and other small animals.

    Spotlight On... features Montana native plants that are currently on display in our natural areas.  Have a plant that you'd like to see featured?  Let us know!

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