Fraxinus nigra
black ash
Native to North America
Overview
Fraxinus nigra is a deciduous tree in the olive family, reaching 40-65 feet (12-20 m) tall with a slender, open crown and a trunk diameter of 12-20 inches (30-50 cm). The bark is gray and develops soft, corky ridges that rub off easily when scraped. Leaves are opposite and pinnately compound, 12-16 inches (30-40 cm) long, with 7-11 stalkless leaflets that are dark green above and turn yellow before dropping in early autumn. Small purplish flowers without petals open in April to May before the leaves expand, followed on female and bisexual trees by flattened winged seeds (samaras) 1-1.6 inches (2.5-4 cm) long. It grows in cold wetlands, swamp forests, stream margins, and seasonally flooded ground across northern North America, tolerating saturated soils that exclude many other trees. Growth is slow and the wood separates readily along the annual rings, a trait long used in basket-making. Across most of its range the species faces severe mortality from the emerald ash borer, an introduced beetle whose larvae kill trees within a few years of infestation. It is shallow-rooted and casts light shade, and its early leaf drop leaves a short canopy season.
Native Range
Native to northeastern North America, from Newfoundland and Manitoba south to the northern United States, including the Great Lakes region and northern Appalachians.Suggested Uses
Used in wet woodland restoration, streambank and floodplain plantings, and naturalized landscapes with saturated soil. Planted historically as a source of basket splints. Limited as a street or specimen tree by emerald ash borer pressure.How to Identify
Appearance
Size & Dimensions
Height40' - 65'
Width/Spread25' - 40'
Reaches mature size in approximately 50 years
Bloom Information
Flowers open in April to May, before the leaves emerge. The small, petalless purple flowers are wind-pollinated and not showy. Winged seeds ripen in late summer and may persist into winter.
Detailed Descriptions
Flower Description
purple, inconspicuousFoliage Description
dark green, yellow in autumnGrowing Conditions
Sun Requirements
Requires 6-10 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
Grows in consistently moist to wet, cool soils in full sun to part shade. Tolerates seasonal flooding and heavy, poorly drained clay that excludes many other trees. It is slow-growing and long-lived in undisturbed wetlands, and transplants with difficulty because of shallow, fibrous roots. In cultivation it needs reliable soil moisture and declines in dry, compacted urban sites. Across its native range, emerald ash borer infestation now limits long-term survival and has prompted quarantines on ash wood movement.Pruning
Pruning is done in late winter while the tree is dormant, removing dead, crossing, or damaged branches. The opposite branching forms narrow forks that can split, so codominant stems are taken out while small. Heavy pruning is minimized because wounds close slowly.Pruning Schedule
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winterearly spring