Fraxinus nigra aka Water Ash

Fraxinus nigra, or black ash, belongs to the olive family. This deciduous tree comes from eastern Canada and the northeastern United States. Its range also reaches the north-central United States. It grows in swamps, bogs, and along streams and shores. These sites often hold water or flood for part of the year. Its dark buds and inner bark explain its common name.

Garden dimensions run from 50–65 feet [15.2–19.8 metres] tall and wide. Virginia Tech gives a smaller height of 40–50 feet [12.2–15.2 metres]. The crown can be slender or open and pyramidal. Growth is slow. Mature bark turns grey-brown, with furrows that form block-like sections. The thick twigs range from light brown to grey. Nearly black buds sit opposite each other along them. The green leaves also grow in opposite pairs. Each pinnate leaf has seven to eleven toothed leaflets. Their undersides are paler and bear some hairs. Only the leaflet at the tip has a stalk.

Green flowers open in spring before the leaves emerge. Male flowers form tight clusters; female flowers form loose panicles. Trees often carry male or female flowers on separate plants. PFAF also reports trees with other mixes of flower types. Each fruit is a samara with one seed and one wing. Fruits appear in fall, and wind carries them away. Butterfly and moth larvae feed on the leaves. Fallen leaves feed tadpoles. The tree also shelters birds, mammals, and long-horned beetles.

Black ash grows in full sun or partial shade. It prefers moist to wet soil and withstands some standing water. Deep loam suits it, including loam with a high clay content. It also grows in peat, muck, and sandy loam. It tolerates acidic, neutral, and alkaline soils. NCSU lists USDA zones 2–9. PFAF notes late-frost damage in Britain despite its cold tolerance. Suitable sites include pond margins, stream banks, and naturalized wet areas. With the right conditions, it can serve as a shade tree.

Emerald ash borer has caused severe losses across its native range. Other listed problems include ash flower gall mites and ash diseases. The flexible wood splits into strips for baskets and chair seats. Makers also use it for furniture, canoe ribs, and musical instruments. The bark yields a blue dye. PFAF records traditional medicinal uses for leaves and inner bark. It lists no known edible uses and no known hazards. That does not establish safety for every use.