Growth Form: Smoketree is a shrub or subshrub and rarely a tree, the trunk is short, crooked and intricately branched with smoky gray or silvery branches, all with spiny twigs throughout, similar to the Paloverde the green trunk, stems and branches produce food through photosynthesis.
Leaves: Smoketree may be leafless most of the year with the leaves falling off early in the spring, thus the ability to photosynthesize, the few leaves are green or silvery in color; the silvery or smoky colored leaves, from a distance give a hazy appearance and thus the common name "Smoketree".
Flower Color: Smoketree has showy dark purple, violet or indigo-blue pea-like flowers, the fruit is an egg shaped pod with 1 or 2 seeds.
Flowering Season: April to June, slightly later in California, June to July and October to November.
Elevation: 1,500 feet (457 m) or lower; below 1,200 feet (366 m) in California.
Habitat Preferences: Desert sandy washes.
Recorded Range: In the United States Smoketree is found in the southwest in AZ, CA and NV. In Arizona is occurs in the west, central and southern parts of the state, in southeast California and southeast Nevada. It is also native to Baja California and northwest Mexico.
Genus Information: In North America, USDA Plants Database lists 8 species and accepted taxa overall for Psorothamnus. Worldwide, World Flora Online includes 19 accepted species names and a further 15 scientific names of infraspecific rank for the genus.
The genus Psorothamnus was published in 1919 by Per Axel Rydberg, (1860-1931).
In the Southwestern United States: Arizona has 7 species of Psorothamnus, California has 6 species, Nevada has 5 species, New Mexico and Texas each have 1 species and Utah has 4 species. Data approximate, subject to revision.
Comments: 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.
Smoketree, Psorothamnus spinosus has attractive flowers, the flowers and their seeds may be visited by hummingbirds and/or small mammals including rodents and granivorous birds in search of nectar or food.
Beneficial Value to Butterflies, Honey Bees and Insects
Smoketree, Psorothamnus spinosus has attractive flowers, the flowers and their plants may be visited by butterflies, moths, flies, honeybees, Native Bees and other insects in search of food and nectar.
****Special Value to Native Bees****
According to The Xerces Society for Invertebrate Conservation or other source, Smoketree, Psorothamnus spinosa, is recognized by pollination ecologists as attracting large numbers of native bees, specifically Bumblebees (Bombus spp.). Click here for more information on their Pollinator Conservation Program.
Etymology:
The genus “Psorothamnus” (Psorotham'nus:) is from the Greek psoros, "mangy, scabby," and thamnos, "bush," thus "scabshrub."
The genus Psorothamnus was published in 1919 by Per Axel Rydberg, (1860-1931).
The species epithet “spinosus” (spinos'us:) is from Latin for "thorny."
The original taxon “Dalea spinosus” was first described in 1854 by Asa Gray, (1810-1888), and later as Psorothamnus spinosus in 1977, by Rupert Charles Barneby, (1911-2000).
Ethnobotany - Native American Ethnobotany; University of Michigan - Dearborn
