Although Rhus aromatica, alternatively known as R. trilobata, is native to Idaho, all the populations in the Boise area appear to have originated from planted progenitors. This conclusion is based on: 1) the lack of any collections, or any of my own observations, within the area prior to 1995; and 2) by the shrub’s apparent absence from undisturbed habitats and restriction to sites where restoration and wildlife habitat improvement efforts were a strong likelihood.
The use of Rhus aromatica without any varietal designation follows the Jepson eFlora. This differs from the PLANTS database (and many other earlier references), which uses var. trilobata for most western populations, and also the 2018 edition of Flora of the Pacific Northwest, which includes var. trilobata in an expanded circumscription of var. aromatica. In that the question of varieties within R. aromatica is evidently uncertain, it seems best to stick with only the species name at present.
One common name that was used previously, squawbush, has been dropped as pejorative.