Robinia x ambigua
These fairly fast-growing trees are 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 the plants often spread by suckers.Robinia x ambigua
A hybrid between R. pseudoacacia and R. viscosa, this seldom-grown, pink-flowering locust grows to 40 ft. tall and nearly as wide. Its varieties are better known.
‘Decaisneana’. Grows to 40–50 ft. tall and 20 ft. wide. Flowers are like those of R. pseudoacacia, but the color is pale pink.
‘Idahoensis’ (Idaho Locust). Moderately fast growth to a shapely 40 ft. tall and 30 ft. wide. Bright magenta-rose flowers in 8-in. clusters; one of the showiest of locusts in bloom. Good flowering tree for Rocky Mountain gardens.
Compact, uniform plant grows to about 10 in. tall and 12 in. wide and is loaded with large flowers. Ea...
Wild species (for which seed is available) grows to 2–4 ft. tall (possibly to 6 ft. under ideal ...
Mediterranean native to 2 1/2 ft. tall and 1/2 ft. wide. Bears so-called everlasting flowers, with dai...