Black Locust
Robinia pseudoacacia · Deciduous Broadleaf Hardwood
Plant Family
Fabaceae (Legume family)
Tree Category
Flowering Shade Tree
Variety / Cultivar
Straight species (likely)
Hardiness Zones
USDA Hardiness Zones 4 through 8.
About This Tree
An upright, fast-growing tree with an irregular, open-branching crown. It is known for its pendulous clusters of fragrant white pea-like flowers and its ability to fix nitrogen in the soil. It often develops a somewhat ragged, architectural form as it ages.
Leaf Characteristics
Pinnately compound leaves, 6-14 inches long, with 7-21 oval, blue-green leaflets. Leaflets have smooth margins and are arranged alternately on the stem. Foliage turns a pale yellow in the autumn.
Bark Characteristics
Deeply furrowed and thick, dark gray to brown bark that develops a distinctive ropey, interlacing ridge pattern resembleing a lattice as the tree matures.
Growing Information
Origin Region
Native to the Appalachian Mountains and the Ozarks of the United States; widely naturalized across North America and Europe.
Growing Season
Leafs out in late spring (one of the last trees to do so); flowers from May to June; seeds ripen in autumn and hang through winter; dormant in late autumn through winter.
Sunlight & Water Needs
Full sun preferred; shows high drought tolerance once established. Adaptable to various soil types including poor, rocky, or sandy soils; performs well in dry to medium moisture.
Mature Size
Reaches 30-50 feet in height with a 20-35 foot spread. It is a fast-growing tree with a moderate lifespan of 60-90 years.
Special Characteristics
Highly durable and rot-resistant timber used for fence posts and ship building; nitrogen-fixing roots improve poor soils; extremely fragrant flowers produce high-quality honey (Acacia honey); however, it is considered invasive in some regions outside its native range.
Wildlife & Ecology
Excellent nectar source for honeybees and butterflies; provides nesting sites for cavity-nesting birds; seeds are eaten by bobwhite quail and other game birds, though parts of the tree are toxic to livestock.