Family Oleaceae > Tribe Oleeae > Subtribe Fraxininae.
There are around 65 species of Ash trees with 5 naturalised in Australia.
Most are trees 10 to 40 m high with a trunk that can be up to 2 m across.
There are a few smaller trees and shrubs from 3 to 8 m.
Greyish bark on young trees is smooth and may have lenticels (small nodules).
Bark on older trees becomes rough with longitudinal cracks and fissures.
It may form plates that are vertical or diamond-shaped or become scaly.
Twigs can be round or 4-angled in cross section and smooth or hairy.
The white or reddish-brown hairs are gradually lost.
Leaf scars on the trunk have a flattish or curved top.

Almost all trees are deciduous.
Leaves are opposite or rarely in whorls of 3 at the branch ends.
They are almost always pinnate with rare simple or trifoliate leaves.
Petioles, from 1.5 to 10 cm long may have few to dense hairs.
The leaf midrib may also have hairs, be grooved or have wings on the sides.

Leaves, from 5 to 50 cm long have 5 or 7 (3 to 25) leaflets.
Leaflets may have no petiolule or one up to 15 mm long.
Like the petiole the petiolules may have a swollen base and be smooth or hairy.
Leaflets can be ovate, elliptic or lance or diamond-shaped.
There may be shallow to deep teeth or lobes near the tip or on all the edge.
The upper surface may have a few hairs but the lower often has sparse to dense ones.

Branched clusters of flowers (panicles) are terminal on the main or short side branches, or axillary.
From 5 to 30 cm long they can have dense or sparse flowers.
Flowers can appear before, with or after the mostly deciduous leaves.
Flowers, a few mms long are on a pedicel 2 to 5 mm long.
Stalks and pedicels may be smooth to densely hairy.

The panicles may have no bracts, ones that fall early or ones that persist.
The linear, spoon or lance-shaped bracts are 2 to 10 mm long.
They can be smooth or hairy, sometimes with thick woolly hairs.

Flowers can be bisexual or unisexual with male and female on different trees.
There may be no calyx or a bell-shaped one around 1.5 mm long with 4 small lobes or a nearly flat top.
There may be some hairs on the outer surface.
There may be no petals, some that fall early or persistent 2 to 7 mm ones with their bases fused and 4 lobes.
Petals are almost always white but occasionally they have a yellowish tint.

There are 2 stamens inserted onto the base of the corolla.
The anthers lie at about the level of the corolla lobes.
The superior ovary has 2 locules with 2 ovules in each, one style with a sometimes bi-lobed stigma.

The fruit are a samara with a wing attached to the flat seed.
They are spatula-shaped and 1.5 to 5 cm long by 2.5 to 8 mm wide.
The wing usually only extends along the upper (distal) part of the seed (nutlet) but it may almost surround it.
They are occasionally twisted, can be red, purple or brown and have hairs that are sometimes glandular.