Overview
Juglans nigra is black walnut (eastern black walnut), a large upright deciduous tree growing 50-75 feet (15-23 m) tall and 50-75 feet (15-23 m) wide. Pinnately compound leaves with 15-23 leaflets each 2-5 inches (5-13 cm). Turns yellow in fall — drops early (September-October). Round green-husked nuts 1.5-2 inches (4-5 cm) with edible kernels inside extremely hard shells. Deeply furrowed dark brown-black bark. In Juglandaceae. Native to eastern and central North America. Produces juglone — a chemical compound released from roots, leaves, and nut husks that inhibits the growth of many other plants (allelopathy). The zone of juglone toxicity extends 50-80 feet (15-24 m) from the trunk. This allelopathy is the primary limitation for landscape use. The nut husks stain skin and surfaces permanently brown-black. Thousand cankers disease threatens western populations. The wood is among the most commercially valued North American hardwoods. Deer-resistant. Drought-tolerant once established. Toxic (unripe husks). Zones 4-9. Full sun. Growth rate is moderate.
Native Range
Native to eastern and central North America — from Massachusetts to Minnesota, south to Florida and Texas. Found in rich bottomlands, river valleys, and mesic slopes.Suggested Uses
Grown as a specimen tree and timber tree in large open landscapes spaced 50-75 feet (15-23 m). Juglone allelopathy limits companion planting — site away from gardens and sensitive plants. Edible nuts. Commercially valued wood. Native to North America. Deer-resistant. Zones 4-9.How to Identify
Appearance
Size & Dimensions
Height50' - 75'
Width/Spread50' - 75'
Reaches mature size in approximately 20 years
Bloom Information
Mid spring (April-May). Inconspicuous greenish flowers — male catkins 2-4 inches (5-10 cm), female flowers tiny in terminal clusters. Wind-pollinated. 2 weeks. Round green-husked nuts 1.5-2 inches (4-5 cm) ripen October.Detailed Descriptions
Flower Description
Greenish, inconspicuous; male catkins 2-4 inches (5-10 cm), female flowers tiny in terminal clustersFoliage Description
Dark green, alternate, pinnately compound with 15-23 leaflets each 2-5 inches (5-13 cm) long, serrated; emerging yellow-green in spring; turns yellow in fall — drops early (September-October)Growing 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). Deep well-drained soil pH 6.0-7.5. Juglone allelopathy — do not plant juglone-sensitive species within 50-80 feet (15-24 m). Nut husks stain permanently. Prune in late summer to fall (August-October) — spring pruning causes sap bleeding. Thousand cankers disease in western US. Deer-resistant. Zones 4-9.Pruning
Prune in late summer to fall (August-October) — pruning in late winter or spring causes heavy sap bleeding. Develop a strong central leader when young. Remove dead, crossing, or low-hanging branches. The wood is commercially valued — damaged branches may be worth salvaging.Pruning Schedule
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