Black Locust 'Purple Robe' (Robinia pseudoacacia 'Purple Robe'): Deep Pink Blooms on a Tough Tree

'Purple Robe' is a striking cultivar of black locust (often called yellow false acacia or yellow locust) selected for its long, dense racemes of deep rosy-purple, fragrant flowers. It retains the species' legendary toughness—drought tolerance, nitrogen fixation, and rapid growth—while offering superior ornamental value.

Botanical Profile

• Family: Papilionaceae (or Fabaceae subfamily Faboideae)
• Genus: Robinia
• Species: pseudoacacia
• Cultivar: 'Purple Robe'

Features

Flowers are darker and more purple than the species' white, borne in 4–8 inch pendulous clusters in late spring. Leaves are pinnately compound, blue-green, turning yellow in fall. The tree grows 30–40 feet tall with an upright, irregular crown. Bark is deeply furrowed, dark, and rope-like. Thorns on young growth.

Culture and Caveats

Extremely adaptable: poor, dry, sandy, or rocky soils; drought; pollution; salt. Fixes nitrogen. Hardy in USDA zones 4–8. However, it can spread aggressively by root suckers and self-seeding, and is considered invasive in some regions. Wood is brittle; branches may break in storms. Borers and leaf miners can be problematic.

Uses

Specimen for difficult sites, reclamation, erosion control, pollinator gardens (with management). Best where suckering can be contained (mowed lawn, pavement).