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Fraxinus nigra Marsh. Black ash

New shoots at branch ends, and extended female flower clusters

Also known as: swamp ash, loop ash.

Habitat

Black ash is typical of swampy woodlands that have moving water and stream banks, in north, central, and western New Brunswick. It may be associated with species such as red maple, speckled alder, balsam poplar, eastern white cedar, and black spruce but, because it is shade intolerant, it grows only in relatively open situations.

Streamside tree in summer

Form

Black ash is a small tree that grows to heights of up to 18 m and to stem diameters of up to 40 cm. The crown is narrow and rather open, becoming rounded at the top, with ascending or arching and up- turning branches.

Morphology

The leaves are deciduous, pinnately compound, 20–45 cm long, and borne oppositely in pairs with each pair parallel to the previous one. Each leaf has seven, nine, or eleven leaflets, with nine being the most common number. The leaflets are stalkless, 10–16 cm long, long oval to broadly lanceolate, with finely and sharply toothed margins, and both surfaces hairless, except for distinct tufts of hair at the bases where the leaflets join the rachis. In the fall, the leaflets tend to shrivel as they turn brown, and then whole leaves are shed.

Twigs of three ashes; white ash (left), red ash (right), and black ash (center)

The twigs are stout, green with purple, raised lenticels when young, becoming pale greyish brown or tan with the lenticels still noticeably raised from the otherwise smooth hairless surfaces as small, pale, vertically elongated mounds. The buds are dark brown to black, or sometimes pale brown, and closely downy. The terminal bud is broadly flame shaped when viewed from one side, and more dome shaped if turned 90o, with the uppermost pair of lateral buds usually some distance below and separated from it by a portion of twig surface. The lateral buds are smaller and mostly rounded, each set above, or only slightly indented into the upper edge of, a longitudinally oval to shield-shaped leaf scar that carries almost a ring of tiny vein scars.

Fruits forming on flower clusters of a female tree

The flowers are borne from lateral buds in oppositely branched, extended clusters, the male ones being somewhat more compact in bloom than the female ones. Male and female flower clusters occur on different trees, so it is only on female trees that the flowers go on to produce fruits. The 25- to 40-mm long fruits each have a slightly swollen, broadly oval, basal seed pocket that tends to merge all around into a flattened, broadly elliptical, often somewhat twisted wing, that may be notched at its rounded tip.

Fruits-the seed pockets are scarcely distinct and the twigs are twisted

The bark is grey and roughened with rounded, soft, corky ridges on young trees. On older trees, the bark is grey with near-vertical, narrow, scaly strips.

Bark of an older stem, 15 cm in diameter

Notes

The brown ring-porous wood of black ash is straight grained, tough, and flexible, but not as hard or strong as that of white ash. It takes bending well. It can be used for snow shoes, barrel hoops, canoe ribs, and woven basketware. For the latter, wet black ash wood is pounded to separate it into thin slats. The pounding causes the thin-walled, large vessel elements (pores) of the early wood of an annual ring to break, so the wood is separated almost into annual sheath widths.

Corky bark of a young stem, 2.5 cm in diameter

A disease or decline of unknown nature has killed many black ash in at least the Fredericton area over the last 15 years. (See the Notes section for white ash for possiblecauses of the ash dieback.)

As indicated in the notes for white ash, the descriptions of the three native ash species should be compared for easy species recognition.