Baccharis salicifolia is a blooming shrub native to the sage scrub community and desert southwest of the United States and northern Mexico, as well as parts of South America. Its usual common name is mule fat; it is also called seepwillow or water-wally. This is a large bush with sticky foliage which bears plentiful small, fuzzy, pink, or red-tinged white flowers which are highly attractive to butterflies. It is a host plant for the larval stage of the fatal metalmark butterfly, and the adult stage also nectars on the flowers.

The long pointed leaves may be toothed and contain three lengthwise veins. It is most common near water sources.

The seed is wind-distributed.

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