Black Locust, False Acacia
Kingdom: Plantae, Division: Magnoliophyta, Class: Magnoliopsida, Order: Fabales, Family: Fabaceae, Genus: Robinia, Species: Robinia pseudoacacia · Fabaceae (Legume/Pea family) · Compound, pinnately arranged with 7 to 21 leaflets per leaf; deciduous.
Species
Robinia pseudoacacia
Leaf Type
Compound, pinnately arranged with 7 to 21 leaflets per leaf; deciduous.
Family
Fabaceae (Legume/Pea family)
Shape
Individual leaflets are oval, elliptical, or ovate with a rounded base and a slightly notched or rounded apex.
Size
Whole leaf spans 8-14 inches long; leaflets are approximately 1-2 inches long and 0.5-0.75 inches wide.
Margin
Entire (smooth transitions along the edge) and very slightly thickened.
Arrangement
Alternate arrangement on the branch; leaflets are usually opposite or sub-opposite along the central rachis.
Rarity
Very Common; often considered invasive or weedy outside its core native range.
Color & Pattern
Bluish-green to dark green upper surface; paler green underside. No variegation; turns pale yellow in autumn.
Venation Pattern
Pinnate venation with a distinct midvein on each leaflet; lateral veins are faint and interconnected.
Texture & Surface
Smooth (glabrous) and slightly thin or papery; may feel slightly leathery on older growth. Dull to matte finish.
Description
A fast-growing deciduous tree reaching 30-80 feet. It features deeply furrowed, dark brown bark that resembles braided rope. In spring, it produces drooping clusters of fragrant white pea-like flowers, followed by flat, brown seed pods.
Key Features
Compound leaves with rounded leaflets; pairs of sharp spines (stipular spines) found at the base of each leaf on young branches.
Habitat
Disturbed areas, forest edges, meadows, and roadsides. Prefers full sun and well-drained soil but is highly adaptable.
Geographic Range
Native to the southeastern United States (Appalachians and Ozarks) but naturalized throughout North America, Europe, and Asia.
Condition Notes
Excellent; leaflets appear healthy with turgid structure and vibrant green color. Minor water droplets visible on the surface suggest recent rain.
Interesting Facts
The wood is exceptionally hard and rot-resistant, often used for fence posts and ship masts. It is a major nectar source for honeybees, producing famous 'Acacia' honey.
Medicinal & Uses
Used for heavy construction, fuel wood, and erosion control. Flowers are sometimes used in fritters, but other parts are toxic. Highly valued in landscaping for poor soils.
Ecological Role
Nitrogen-fixing pioneer species that improves soil quality. Provides nesting sites for birds and is a critical early-season food source for pollinators.
Similar Species
Honey Locust (Gleditsia triacanthos) which has smaller leaflets and larger branched thorns; Tree of Heaven (Ailanthus altissima) which has notched leaflets with glands at the base.
Foraging Tips
Look for the fragrant white flower racemes in late spring. Identification is easiest by looking at the ropey bark and checking for pairs of thorns on new growth.
Toxicity Warning
Moderately Toxic. Bark, leaves, and seeds contain toxalbumins (robin and phasine). If ingested, causes nausea, vomiting, and depression in humans and livestock.