Robinia

Locust
Fabaceae (Leguminosae)
Deciduous, Trees

Fairly fast growing plants, well adapted to hot, dry regions. Leaves are divided like feathers into many roundish leaflets. Clusters of white or pink, sweet pea-shaped flowers bloom from midspring to early summer, followed by bean-like pods about 4 in. long.

Locust trees tolerate poor soil and can get by on little or no water, but they do have some drawbacks: their wood is brittle, roots are aggressive, and plants often spread by suckers.

Robinia neomexicana

Native from California's mountains to Arizona and New Mexico, this thorny plant usually grows about 6 ft. high and wide, but can become a 30-ft. tree. It produces drooping, 6-in. clusters of inch-wide pink flowers.

Robinia pseudoacacia

Native to the eastern and central United States. Fast growth to 40 to 75 ft. tall, 30 to 60 ft. wide, with rather sparse, open branching habit. Deeply furrowed brown bark. Thorny branches. Leaves divided into 7-19 leaflets, each 1-2 in. long. White, fragrant, 1/2–3/4-in.-long flowers are held in dense, pendent clusters that reach 4-8 in. long.

Robinia x ambigua

A hybrid between Robinia pseudoacacia and R. viscosa, this seldom-grown, pink-flowering locust grows 40 ft. tall and nearly as wide. Its varieties are better known.

'Frisia'

To 50 ft. tall, 25 ft.wide. New growth is nearly orange; mature leaves are yellow, turning greener in summer heat. Thorns and young wood are red.