Common Name(s): Alamos Pea Flower, Vara Prieta, Palo Piojo

Synonym(s):

Family: Fabaceae

Native To: Sonora and Sinaloa, Mexico

Native Habitat: Arroyos and half-shady thornscrub.

Growth Habit: Single or multi-trunked tree growing 10 to 15 feet tall.

Flowering: May through August

Distinguishing Characteristics: Leaves are odd-pinnate, and can range in size up to 10 inches long with 9 to 13 leaflets. Leaflets are oval, smooth margined, with a tiny pointed tip at the apex, and 1 to 2 inches long. The leaves fall shortly after the summer monsoons end, although the UA trees never seem to lose all of their leaves. New growth is very light green, almost white, because of many small hairs covering the surfaces. Flowers appear when the plant is mostly leafless, and are produced from the leaf axils either singly or in clusters of two. Petals range from deep red to dark maroon with centers that are lime green. The pods are 2 to 3 inches long, and in the fall, when ripe, burst open with a loud popping noise. This method of dispersal allows the seeds to be flung great distances from the parent tree. The bark is gray-brown with vertical fissures and noticeable lenticels.

Natural History and Cultivation Notes: The genus name honors French botanist, Adolphe T. Brongniart. The species name refers to the city of Alamos, Sonora, where it was first collected in 1890 by Edward Palmer. Hummingbirds are frequent visitors of the dark maroon colored flowers, but they may not be effective pollinators.

The Desert Legume Program has been testing the species at the Campus Ag Center in Tucson (a cold site where they froze to the ground but re-sprouted after 15 F in 1996), and at the DELEP test fields in Yuma (where they add 3-4 feet of growth each season.)

According to Richard Felger’s work in Sonora, the species is damaged at temperatures lower than 25 F. Although one of the UA trees is situated on a western exposure, and the other on an eastern exposure, both trees depend on the heat retention of their buildings to protect from winter cold. Such protection should not be needed in Phoenix, Yuma, or even San Diego.

Ethnobotany:

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