Japanese apricot (ume) bonsai

Placement

Prunus mume is a deciduous tree from East Asia, grown outdoors all year. During the growing season it needs full sun, at least five to six hours of direct light a day: the buds for next year’s flowers form during the warm months.

Winter calls for more care. Ume tolerates some frost, but its roots, cramped in a shallow pot, fear prolonged freezing, and hard cold dries out young shoots and damages buds about to open. Leave it outside until the first frosts so it goes dormant, then shelter it in a cold frame, a cold greenhouse, or an unheated shed. Ventilate on sunny days: a long warm spell wakes the tree too early. In spring, once it starts growing again, protect it from late frosts.

The flowers open on bare wood in late winter or the very beginning of spring, often before the leaves. White or pink, sometimes red depending on the cultivar, they are very fragrant; small yellowish fruits, edible but sour, can follow.

Soil mix

Use a free-draining mineral bonsai mix: ume tolerates neither standing water nor poor, dry soil. A common mix for deciduous trees combines 50% akadama, 25% pumice, and 25% lava rock; sift the akadama to remove the dust. If you cannot check on watering often, raise the share of akadama a little.

Watering

Keep the mix moderately moist, never soggy, and let the surface dry slightly between waterings. Needs vary a great deal: in midsummer, in full leaf, the tree drinks far more than in winter, when it is dormant. Feel the mix rather than following a schedule. Never let the root ball dry out completely, especially in spring while the buds swell: running short of water then makes buds and flowers drop. Conversely, overwatering and a poorly draining mix lead to root rot.

Fertilizer: feed from spring to early fall with a balanced solid organic fertilizer, renewed every four to six weeks depending on the product. Regular feeding in summer supports the next bloom, but too much fertilizer mostly produces leaves and weak branches. Do not feed in winter; a light dose in late winter, before growth starts, can encourage earlier flowering.

Pruning

Everything follows one rule: ume blooms on the previous year’s wood. The buds form during the growing season, so hard pruning in fall, in winter, or just before bloom removes the flowers.

The main pruning comes right after flowering: cut back hard the branches that bloomed, and remove dead wood, diseased or crossing branches, and growth that spoils the outline. During the season, pinch new shoots to keep the branching compact: in early summer, shorten them to five or six leaves, then to about three leaves at the second trim, once the summer growth has hardened in fall. Side shoots are shortened by one leaf. Avoid pruning in winter, when cuts easily become infected, and promptly remove any parts that die back.

Ume’s character lies in its trunk: with age, the bark cracks deeply and gives old trees a stern look; hollowed and carved trunks are also seen. It is grown in small sizes too, in the shohin category.

Wiring

Style the tree as the buds break in spring, after flowering. Choose aluminum wire, easier to handle on a deciduous tree, about one third the thickness of the branch, wound at roughly 45°. Anchor it with one or two turns around the trunk, wire every branch you plan to move before bending, and bend while supporting the outside of the curve with your fingers. Avoid bending the same branch repeatedly, and protect thick branches with wet raffia.

Branches take a few months to hold their new position, but during growth the bark can be marked within one to four months: check the wire and remove it by cutting it at every turn rather than unwinding it.

Repotting

Repot a young tree every two or three years and an older one every three to five years; a vigorous, well-established tree can need repotting every year. Do it in early spring, right after flowering and before growth starts. Gently untangle the roots, remove dead or rotting ones, and never take off more than 30% of the root mass. Replant in a free-draining mix, water thoroughly, keep the tree out of direct sun for a few weeks, and wait before feeding.

Propagation: cuttings are quicker and more reliable than seed. Take semi-hardwood cuttings in late summer, dip the base in rooting hormone, and keep them humid; they root in a few weeks to a few months. Hardwood cuttings are taken in late winter, layering is done in summer, and grafting in winter or spring. To grow from seed, soak the pits in cold water for a few days; germination takes several weeks.

Pests and diseases: aphids, scale insects, and spider mites can move in; insecticidal soap or neem oil deals with them. In humid weather, powdery mildew and other fungi appear: space trees apart so air can move. The species is also prone to bacterial canker, silver leaf, honey fungus, and blossom wilt. The same symptom can have several causes: always check watering and drainage.