Mule fat has two phenological forms. (Phenological refers to periodic biological phenomenon that are related to climatic conditions.) In the summer this native shrub has terminal inflorescences and the leaves are more likely to be toothed. In spring and fall the inflorescences are lateral with toothless leaves. These two forms with different flower placement caused the plant to be classified as Baccharis vinimea or Baccharis glutinosa for the summer and other seasonal forms, respectively. Currently both forms of this shrub are classified as Baccharis salicifolia, although the issue does not appear to be fully resolved.
Mule fat (The unusual common name comes from the fact that mules would bloat after eating the plant.) is found through much of California and the Southwest, extending into Mexico and South America at elevations below 2,500 feet. Generally in the valleys, mountains and along the coast, mule fat is associated with streamsides and riparian forests or other wet areas. In arid areas of the West mule fat is equally likely in wetlands or grasslands and sage scrub.
A large, slightly sticky shrub that grows from 6 to 12 feet in height, mule fat has straight ascending stems. The alternate, evergreen leaves are linear or narrowly lance-shaped and resemble willow leaves. There are three midveins in the leaf blade with the midnerve much stronger than the two lateral veins. The creamy white flowers are all discoid and are arranged in heads. The flower heads are unisexual with staminate and pistillate flowers on different plants (dioecious). The involucral bracts surrounding the flower heads are golden brown or tinged with pink. Mule fat fruits are achenes (single dry seeds).
Native Americans used mule fat decoctions for eyewashes and to cure baldness. During times of famine, the young shoots were roasted and eaten. The plant was also used as a fire starter with a hand drill because of its flammability. The stems were also formed into arrow foreshafts and spears.
The genus name, Baccharis, comes from the Greek god of vegetation, later the god of wine. “Salicis”, the Latin word for “willow”, combined with the Latin word for foliage forms the species designation. Seep willow and water wally are other common names for B salicifolia.
These specimens were photographed in May near the pond on the Arboretum Loop Trail near the Sundial Bridge in Redding CA (Shasta County).