Olneya tesota aka Desert Ironwood

Olneya tesota is known as desert ironwood or tesota. This member of the pea family grows as a tree or shrub. Its native range spans southern California, Arizona, and northwestern Mexico. It occurs in Sonora and both states of Baja California. It grows in desert washes below 1,970 feet [600 metres]. It also grows on sandy or gravelly mesas and rocky foothills.

The tree has a short trunk, sometimes split into several trunks. Its dense crown spreads wide. Sources place its height near 30 feet [9 metres]. Oregon State records a champion reaching 44 feet [13.4 metres]. Young bark is smooth, shiny, and gray to gray-brown. Older bark turns darker and breaks into scales or loose strips. Smooth and rough patches may meet on the same trunk. Slender green twigs turn gray-brown with age. Pairs of sharp spines grow at the leaf bases.

The leaves grow in an alternate pattern along the stems. Each pinnate leaf has several pairs of small leaflets. Sources report six to fifteen pairs, with rounded leaflet tips. The foliage is gray-green to blue-green, with fine hairs. Leaves have smooth edges and measure roughly one to three inches. The plant keeps its leaves through much of the year. Long droughts can make it shed them. Temperatures below 36°F can also cause leaf loss. Small clusters of pea-shaped flowers appear in late spring. Bloom can extend into early summer. Each flower has five unequal petals. Colors include pink, purple, magenta-red, and white. The flowers have a scent. Brown pods ripen in late summer. They measure about two to three inches long. Hairs cover the pods, which bulge around their seeds. Each pod holds one to five shiny brown seeds.

Grow desert ironwood in full sun and well-drained soil. Plants For A Future also lists light shade as suitable. It lists sandy, loamy, and clay soils as suitable. Its pH range spans mildly acid through mildly alkaline soils. That source reports a preference for moist soil and moderate growth. Oregon State lists hardiness to USDA Zone 9. Plants For A Future calls for a climate with little frost. Oregon State reports poor growth in seaside sites.

Garden uses include screens, specimen trees, and street planting. Its broad crown and flowers give it landscape value. The tree also draws birds. Its wood is very heavy and hard enough to dull saws. People eat the seeds raw or cooked. They also roast them or grind them into meal. Plants For A Future compares their taste with peanuts. It reports no known hazards or medicinal uses. The sharp spines remain a physical hazard when handling the plant.