Robinia neomexicana aka New Mexico Locust

Robinia neomexicana is a deciduous shrub or small tree. Its common names include New Mexican locust and desert locust. It belongs to the pea family, Fabaceae. Its native range spans the southwestern and south-central United States. It also reaches northern Mexico, including Sonora and Chihuahua. It grows in mountain canyons and on plains. Wild plants often grow beside streams in sunny sites. These habitats lie at elevations of 3,940–8,200 feet [1,200–2,500 metres].

Sources differ on its size, from 6.6 feet [2 metres] to 25 feet [7.5 metres]. Oregon State gives the larger size for landscape plants. Its upright growth can take a shrub or tree form. Roots send up many suckers, which form dense thickets. The gray-brown bark has shallow grooves and flat, scaly ridges. The stems bend in a zigzag and bear reddish hairs. Two spines grow at each leaf scar. Alternate, pinnate leaves have 11–19 oval leaflets with smooth edges.

The pea-shaped flowers hang in short clusters. Their color ranges from near white to pink or purple-pink. Each flower has both male and female parts. Virginia Tech places bloom in late spring. Plants For A Future gives July through August instead. The fruit is a flat brown pod with gland-tipped hairs. Pods measure about two to four inches long. The leaves drop at the end of the growing season.

Grow this plant in sun and soil that drains well. It also tolerates light shade, according to Plants For A Future. Sandy, loamy, and clay soils can all suit it. It accepts mildly acid, neutral, and mildly alkaline soil. It tolerates drought, poor soil, and air pollution. Plants For A Future lists USDA zones 4–8. Oregon State gives cold hardiness to zone 5. Brittle branches can break in wind. Rich soil encourages coarse growth that breaks more easily. Plants For A Future recommends pruning in late summer to limit bleeding.

Its flowers give it value as a specimen plant. Root suckers can help hold soil on banks. It fixes nitrogen and can regrow after coppicing. Its tough, durable wood has served as fence-post material. Plants For A Future records food uses for flowers and pods. It also records cooked seeds, but warns that seeds may be poisonous. The same warning covers bark and roots. That conflict makes the seed food record unsafe to follow.