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Robinia pseudoacacia
black locust
Central Appalachian and Ozark regions of eastern North America — limited native range in the mountains of Virginia, West Virginia, Pennsylvania south to Georgia, and in the Ozarks of Missouri and Arkansas; widely naturalized and invasive far beyond its native rangeLearn more
Key Features
Attracts PollinatorsAttracts ButterfliesDeer ResistantDrought TolerantFragrant (strong)
Native to North America
Maintenancehigh
Overview
Robinia pseudoacacia is black locust (false acacia), a large upright deciduous tree growing 40-70 feet (12-21 m) tall and 25-35 feet (7.5-10.5 m) wide. White pea-shaped flowers 0.75 inch (2 cm) in pendant racemes 4-8 inches (10-20 cm) in May-June — strongly fragrant (sweet heavy scent) and a valued honey source. Bright to medium green pinnately compound leaves with 7-19 oval leaflets each 1-2 inches (2.5-5 cm). Late to emerge in spring (May). Paired stipular thorns 0.5-1 inch (1.3-2.5 cm) at each leaf node on young growth. Deeply furrowed dark bark on mature trunks. In Fabaceae. Nitrogen-fixing. Native to the Appalachian and Ozark regions — widely naturalized and classified as invasive far beyond its native range in many US states and in Europe. This invasive suckering and seeding is the primary limitation. Spreads aggressively by root suckers — individual suckers emerge 20-50 feet (6-15 m) from the parent. Weak-wooded — branches break in ice storms and high winds. The thorns on young growth are a hazard. The wood is extremely hard and rot-resistant — valued for fence posts. All parts except the flowers are toxic (robin lectin and robitin). Deer-resistant. Drought-tolerant. Tolerates poor soil, alkaline conditions (pH to 8.5), and salt. Zones 3-8. Full sun. Growth rate is very fast.
Native Range
Native to the central Appalachian and Ozark regions of eastern North America. Widely naturalized and classified as invasive far beyond its native range in many US states and in Europe.Suggested Uses
Grown for erosion control, mine reclamation, and honey production on degraded sites. Nitrogen-fixing. The hard rot-resistant wood is valued for fence posts. Classified as invasive — not recommended for general landscape use in most regions. Aggressive suckers. Thorns. Toxic. Zones 3-8.How to Identify
Appearance
Size & Dimensions
Height40' - 70'
Width/Spread25' - 35'
Reaches mature size in approximately 15 years
Bloom Information
Late spring (May-June). White pea-shaped flowers 0.75 inch (2 cm) in pendant racemes 4-8 inches (10-20 cm). Strongly fragrant. 2 weeks of bloom. Bee-pollinated — valued honey source. Brown seed pods 2-4 inches (5-10 cm) persist through winter.Detailed Descriptions
Flower Description
White, pea-shaped, 0.75 inch (2 cm), in pendant racemes 4-8 inches (10-20 cm); strongly fragrant (sweet, heavy scent); source of valuable honeyFoliage Description
Bright to medium green, alternate, pinnately compound with 7-19 oval leaflets each 1-2 inches (2.5-5 cm); late to emerge in spring (May); turns yellow in fall — drops earlyGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Full sun (6+ hours). Any well-drained soil pH 5.0-8.5 — tolerates poor soil, drought, salt, rocky, and alkaline conditions. Nitrogen-fixing. Classified as invasive in many regions — check local status. Aggressive root suckers. Weak-wooded — branch failures in storms. Thorns on young growth. Prune in winter (January-February). High maintenance. Toxic (all parts except flowers). Deer-resistant. Zones 3-8.Pruning
Prune in winter (January-February). Remove dead, crossing, or weak-angled branches. Remove root suckers to control spread. The deeply furrowed bark on mature trunks is a feature. The wood is extremely hard — use sharp tools. Thorns on young growth — wear heavy gloves.Pruning Schedule
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winter