Mariosousa millefolia (S. Watson) Seigler & Ebinger
Native Geographic Range
Southwestern North America
Cultivation Status in AZ
Cold-deciduous multiple-stemmed shrubs to 10 ft (3 m) high. The bark is pale gray and becomes slightly rough with age. Leaves are bipinnate with 6--14 pairs of pinnae per leaf, each with 20--37 pairs of small leaflets per pinna. White flowers are produced in open, spike-like inflorescences along the stems. Flowering occurs during summer.
Native to southeastern Arizona and adjacent northwestern Mexico on slopes and in canyons at the upper elevations in desert habitats and more commonly in semidesert grassland and oak woodland. In Mexico the species also occurs in thornscrub.
Santa-Rita acacia has rarely been planted in Arizona as a landscape shrub. It is best suited in a naturalistic planting as a background plant. The flowers are showy. The plants have a long dormant period and individual stems tend to die after several years. Occasional irrigation in hot weather helps maintain appearance. The species is hardy to at least 16° F (-9° C). The papery fruits can be a minor litter issue.