Shrubs Of The Great Basin: A Natural History

Tabacco Brush

Tobacco Brush Ceanothus velutinus INDIANS ONCE USED the leaves of C. velutinus as a substitute for tobacco, presumably a poor one, since it is not so used today. Other common names for tobacco brush include snowbrush, in reference to its soft mounds of white flowers in the spring; sticky laurel or varnish leaf ceanothus, because of the sticky, varnishlike coating on the leaves; and mountain balm, since this shrub inhabits montane situations and has a strong characteristic odor, leaving the subjective impression of cinnamon, balsam, or walnut. There is some evidence that its distribution is dependent on an insulating snow cover during the winter, so the term snowbrush would also be appropriate from this standpoint. In any event, this is the only Ceanothus with a significant distribution within the Great Basin, though many more species occur in California and the Southwest. In a region replete with tough plants, tobacco brush has a cast~iron char~ acter. It rarely shows any evidence of grazing or insect depredation, and it is one of the first shrubs to appear after a severe bum. Even though the top of the plant may be burnt to the ground, tobacco brush readily root~sprouts. In addition, the seeds will lie dormant in the soil for a long time until the heat ofa forest fire stimulates them to germinate. Ithas been shown that Ceanothus seeds immersed for a time in hot water will have improved germination rates. Experiments by J. R. Sweeney of the University of California have demonstrated that seeds of California buckbrush, C. cuneatus, will with~ stand dry heat up to 80 degrees C. and germinate as well as those of a con~ trol group kept at a lower temperature. Clarence and Alice Quick, of the California Forest and Range Experi~ ment Station, exposed the seeds of two species of Ceanothus to boiling water for varying periods of time. They found that, after being boiled for twenty 208 TOBACCO BRUSH 209 minutes, 12 percent of the seeds of deerbrush, C. integerrimus, germinated. Seeds of mountain whitethorn, C. cordulatus, were even more resistant. The Quicks obtained a germination rate of 25 percent after mountain white~ thorn seeds had been boiled for twenty~five minutes. Thirty minutes, how~ ever, was apparently too long, since none of the seeds germinated after being treated that long. Tobacco brush and other species of Ceanothus have a very hard seed coat which must be cracked or abraded in some way or else exposed to heat before germination will occur. Even then, germination will not occur unless the seeds are stratified, that is, moistened and stored for a few weeks at temperatures near 0 degrees C. Heating or breaking the seed coat will allow the seeds to imbibe water and swell, but growth will not take place unless they have been exposed to this sort of cold period. The optimum time for exposure to boiling water appeared to vary with the particular sample of seeds. In one case, ninety seconds seemed not to be long enough, although over 95 percent germination was achieved. But in other cases five seconds of exposure produced the best results, with around 80 and 60 percent germination. This would indicate the existence of signifi~ cant genetic differences, resulting in either ecotypes or biotypes. One might assume from this that some deerbrush populations are adapted to hotter fires than others. The Quicks also found that Ceanothus seeds remain viable for a very long time. One batch of deerbrush seeds twenty~four years old showed a 90 percent germination rate, while 92 percent of a tobacco brush seed sample which was twelve years old germinated. The successful pioneering efforts of tobacco brush can be seen on the east slope of the Sierra Nevada, along Interstate 80 where it traverses the site of the infamous Donner Lake fire of 1960. The slopes, once covered with fir, Jeffrey pine, and lodgepole pine, are in many spots now solid stands of to~ bacco brush over a meter high and so impenetrable that even the hardiest hiker avoids them. The Forest Service has recently undertaken a program of spraying some of these areas with herbicide in order to open up sites for tree planting, so persistent is the tobacco brush. Obviously it is of considerable value, despite its unpalatability, because of its ability to rapidly invade a burnt~over area and as a result hold soil in place against what might other~ wise be the disastrous effects of erosion. Like the bitterbrush, the...