07/19/2024
Desert smoke tree (Psorothamnus spinosus) is an unusual, spinescent tree which often defies what we consider as a tree, though it often has a trunk and a canopy. This almost leafless, spiny tree has aromatic foliage and often an irregular canopy and reached about 20’ tall eventually. Dark purple to blue flowers appear in April-June followed by legume seed pods. The foliage is incredibly aromatic. The common name “Smoketree” is a reference to a smoky look from a distance due to the normally gray appearance of the tree, which, in spring, completely changes to a blast of violet or indigo-blue flowers.
Plant in full sun, in very well-drained soil (sandy is the best), and low water once established. Plant hardiness varies (some populations are found pretty north in some cold, Mojave desert areas), but perhaps have a plan for protection if it gets into the low 20s°F.
Important nectar plant—used by hummingbirds, bees, and more. Various granivorous birds and mammals consume the seeds. This is a larval host for the Burns’ buckmoth (Hemileuca burnsi). A very cool parasitic plant lives on species of Psorothamnus, Thurber’s stemsucker (Pilostyles thurberi), which lives inside the tissue of the host until it flowers. If you see brown or pinkish flowers on this plant (the flowers are usually purple for smoke trees) then you might be looking at this cool parasitic plant.
Most often found in sandy desert washes and roadsides in Arizona, California and Nevada, and in neighboring Sonora and Baja California—so, found in both the Mojave and Sonoran Deserts.
This species is in the Fabaceae, the bean family. There are 10 species of Psorothamnus.
Formerly known as Dalea spinosa.
The genus “Psorothamnus” is derived from the Greek psoros, “mangy, scabby,” and thamnos, “bush,” thus “scabshrub” referring to the glandular nature of the genus. The species epithet “spinosus” is from Latin for “thorny.” The former genus, Dalea, honors English apothecary Samuel Dale (1659–1739).
Photo by siempreviva on iNaturalist
