Fraxinus bungeana Seeds | Bunge’s Ash

Bunge's Ash (Fraxinus bungeana) in early spring, covered in clusters of small white flowers before the leaves — Bunge’s Ash (*Fraxinus bungeana*): Oleaceae, a small ash of the dry hills of northern China that flowers white before the leaves.

LATIN NAME: Fraxinus bungeana

COMMON NAME: Bunge’s Ash

Plant Profile

Bunge’s ash is a small tree, four to eight metres in the open, with a compact, rounded crown and a trunk that stays slim and pale grey well into maturity. The leaves are pinnate, with five to seven small, ovate leaflets that are glossy above and slightly hairy beneath, and they open late, after the flowers have finished. The winter buds are dark and pointed, and the twigs are stiff and angular, with a characteristic flattening at the nodes.

The flowering is what makes the tree worth growing. In early spring, before any leaf has moved, the branches carry dense clusters of small white flowers with unusually long stamens, so that the whole crown looks frosted, and the flowers are sweetly scented. They are pollinated by wind and by the first insects of the season, and the fruit that follows is a small, narrow samara, two to three centimetres long, hanging in bunches through the summer. The species is native to the dry hills and rocky slopes of northern China, from Hebei and Shanxi across to Shaanxi, Gansu and Henan, generally between five hundred and two thousand metres, usually on limestone or other basic soils. It is a tree of thin, stony ground and cold winters, and it is much less demanding of moisture than the large ashes of the lowlands.

Science & Biotechnology

Fraxinus bungeana belongs to the section of the genus in which the flowers retain petals, a primitive character within a group where most species are wind-pollinated and petalless. That combination of showy flowers and wind dispersal has made the species useful in studies of the evolution of breeding systems in the olive family, and its position in the genus has been checked with molecular markers. The bark contains coumarins, chiefly fraxin and its aglycone esculetin, together with hydroxycoumarins and secoiridoids, and these compounds have been examined for anti-inflammatory and antioxidant activity.

The genus as a whole is under intense scrutiny because of ash dieback in Europe and the emerald ash borer in North America, and the Asian ashes are of interest as potential sources of resistance. Bunge’s ash has been included in screening trials for both problems, and although it is not a major timber species, its genetic resources are part of the wider effort to understand how ashes defend themselves against stem cankers and wood-boring insects. Work on the species also covers its seed biology, since the samara has a deep dormancy that requires a warm period followed by cold, and its drought physiology, which involves a deep taproot and early stomatal closure.

Uses & Benefits

The wood is hard, tough and flexible, pale in colour and takes a good finish, and it has been used for tool handles, sporting goods and small turnery, though the tree is too small and too scarce to be a timber crop. The bark is used locally as a substitute for Qin Pi, the Chinese drug derived from the bark of related ashes and used for damp heat and eye problems. The substitution is regional and not pharmacopoeial, and the species should not be treated as interchangeable with the official source in any serious preparation.

In the garden the tree is grown for its early flowering and its tolerance of poor, dry, alkaline soil. It is small enough for a suburban garden, it casts a light shade that suits perennials, and its white spring display comes at a time when little else is in bloom. It is also a good street tree in cold, dry climates, where its compact crown and modest size fit under wires and between buildings. The autumn colour is a soft yellow, and the samaras persist into winter, giving the bare tree a fine, delicate texture.

Growing from Seed

The samara contains a seed with a deep dormancy, and germination without treatment is slow and erratic. Sow fresh seed in autumn in a pot of loam and grit, leave it outdoors through the winter, and expect germination the following spring. For spring sowing, give three months of warm, moist conditions at twenty degrees followed by three months at four degrees. Germination is spread over several weeks, and a proportion of the seed may wait until the second year.

Prick the seedlings out into deep pots as soon as they are large enough, since the taproot develops quickly, and grow them on in a cool frame. Plant out in autumn into any well-drained soil, including thin, stony and alkaline ground, in full sun. Stake for the first two years and water through the first two summers, then leave the tree alone. It grows at a moderate pace, adding thirty to fifty centimetres a year, and it begins to flower at about eight years from seed.

Our Take

A modest tree with one excellent season, and a useful one for cold, dry, chalky ground. Sow it fresh, give it a winter outdoors, and it will flower before almost anything else.

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