Black Locust
Robinia pseudoacacia · Deciduous, Broadleaf, Hardwood
Plant Family
Fabaceae (Legume family)
Tree Category
Flowering, Shade, Timber, Nitrogen-Fixing
Variety / Cultivar
Species type
Hardiness Zones
USDA Hardiness Zones 4-9; highly adaptable to urban environments and cold climates.
About This Tree
A fast-growing, medium-to-large tree with an irregular, open-crowned form. It is characterized by its deeply furrowed bark and pendulous, fragrant white flower clusters (racemes) that bloom in late spring. It often develops a crooked trunk and contorted branches with thorns on younger stems.
Leaf Characteristics
Pinnately compound, 8-14 inches long with 7-19 oval, bluish-green leaflets. Arrangements are alternate. Leaf margins are entire (smooth), and foliage turns a pale, unremarkable yellow in the fall.
Bark Characteristics
Dark brown to gray, exceptionally thick, and deeply furrowed into long, interlacing fibrous ridges that often resemble a braided rope in mature specimens.
Growing Information
Origin Region
Native to the Appalachian Mountains and Ozark Plateau in the United States; widely naturalized across North America and Europe.
Growing Season
Leafs out in late spring (often one of the last trees to do so); flowers in May or June with pendulous white clusters; enters dormancy in late autumn; seeds persist through winter.
Sunlight & Water Needs
Full Sun (shade intolerant); low to moderate water needs. It is exceptionally drought-tolerant once established and thrives in well-drained soils, though it can tolerate poor, sandy, or alkaline conditions.
Mature Size
Typically reaches 40-60 feet in height with a spread of 20-35 feet; growth rate is very fast (2-3 feet per year); lifespan is relatively short to moderate (60-90 years).
Special Characteristics
Nitrogen-fixing roots improve soil quality; timber is extremely durable, rot-resistant, and dense; prized for honey production (Locust Honey); highly resistant to rot and termites.
Wildlife & Ecology
Attracts bees and butterflies with high-nectar flowers; provides nesting sites for cavity-nesting birds; seeds are eaten by northern bobwhites and squirrels; acts as a host plant for the Silver-spotted Skipper butterfly.