Japanese apricot

Identification and origin

Prunus mume belongs to the rose family, Rosaceae, along with cherries, plums, and apricots. It was first described as Armeniaca mume. It is native to south-central China, Laos, and Vietnam, where it grows in woods and on rocky hills. It has been introduced to the rest of China, Korea, Taiwan, and Japan. It has been cultivated in China for more than 1,500 years, holds a central place in Chinese gardens, and Japan has several hundred named cultivars.

It is a deciduous, bushy tree with a rounded to oval crown, usually 15–20 ft tall and as wide, sometimes up to 29.5 ft. It grows quickly.

The leaves are alternate, simple, and ovate, 2–4 in long, with a tapering tip and sharply toothed, often doubly serrated edges. Rich green above, they have hairs along the veins underneath and glands on the leaf stalk. They turn yellow in fall. Young stems are green, smooth, and glossy; the bark, light gray and smooth on young trees, becomes furrowed and peels with age.

Flowering is the species’ great asset. The five-petaled flowers, 1–1 in across, open singly or in pairs on bare branches in late winter or the very beginning of spring. Pale pink in the species, they range from white to red depending on the cultivar, in single, semi-double, or double forms, and carry a strong clove scent. They are followed by round, fuzzy drupes 1–1 in across, yellowish green to yellow-orange, ripening in summer. Sour and bitter when raw, they are used in Japan for jellies, liqueur, and pickles.

Among the many cultivars:

• ‘Alba’: single white flowers.
• ‘Bonita’: semi-double rose-red flowers.
• ‘Peggy Clarke’: double deep rose flowers.
• ‘Contorta’: twisted branches and single white flowers.
• ‘Beni-chidori’: compact form, 5–8 ft.

Light

Full sun suits it, but it also accepts partial shade as long as it gets at least two hours of direct sun a day, ideally six or more. Above all, choose a sheltered spot: since it blooms in the middle of winter, cold can damage the flowers and spoil the crop.

Watering

Japanese apricot likes soil that stays moist and tolerates neither dry soil nor standing water. In the ground, keep an eye on dry spells: if the soil dries out deeply, water thoroughly.

In a container, never let the root ball dry out completely. Water when the surface starts to dry, more often during active growth than in winter, when the dormant tree uses little. Keep the mix moist in spring while the flower buds swell: running short of water at that stage makes buds and flowers drop.

Potting mix

In the ground it prefers moist, loamy soil rich in organic matter, slightly acidic and well drained, but it adapts to clay, loam, or sand, whether acidic, neutral, or alkaline, as long as the soil is moderately fertile and never waterlogged. Avoid poor, dry soils. In a container, use a free-draining mix that still holds some moisture.

Temperature

The species is hardy in USDA zones 6 through 9. It withstands harsh winters, around 5–14 °F, but its flowers, which open in midwinter, are vulnerable to frost: hard cold can damage flowers and fruit and kill back young shoots. In a container, the roots are more exposed than in the ground: protect the pot whenever cold persists below 14 °F, for example in a cold frame or an unheated shelter.

Repotting

For a container-grown tree, repot every two or three years in early spring, before growth starts, or right after flowering. Gently untangle the roots, remove dead or damaged ones, shorten the longest without overdoing it, then replant in fresh, free-draining mix. Water thoroughly and keep the tree out of direct sun for a few weeks.

Pruning

Japanese apricot blooms on the previous year’s wood: the buds form during the growing season before flowering. Pruning in fall or winter therefore removes the coming flowers. If pruning is needed, do it right after bloom.

In the ground it needs little attention: promptly remove dead wood, as well as diseased or crossing branches, to open up the canopy. Avoid pruning in winter, when cuts expose the tree to infection.

Propagation

Cultivars are propagated by grafting, done in winter or spring. You can also sow seed: soak the pits in cold water for a few days and sow them in fall in a free-draining mix; germination takes several weeks. Cuttings are quicker and more reliable than seed: softwood cuttings in early summer with bottom heat, semi-hardwood cuttings in late summer dipped in rooting hormone and kept humid, or hardwood cuttings in late winter. Layering is done in summer.

Common problems

Japanese apricot is tougher and more trouble-free than most flowering fruit trees, but several problems can affect it:

• Pests: aphids, scale insects, spider mites, caterpillars (including tent caterpillars), and borers. Trees grafted onto peach rootstock can be attacked by the peach tree borer. Insecticidal soap or neem oil works against aphids, scale, and mites.
• Diseases: bacterial canker, silver leaf, honey fungus, brown rot, and blossom wilt. In humid weather, powdery mildew and other fungi appear: good air movement lowers the risk. In a container, overwatering and poorly draining mix lead to root rot.
• Xylella bacterium: the species is listed as a high-risk host of Xylella fastidiosa.
• Dried flowers or young shoots in late winter: a possible sign of frost on the blossoms.

The same symptom can have several causes: before treating, check watering, drainage, and exposure.

Toxicity

The leaves, stems, and seeds are toxic to dogs, cats, and horses if eaten. In plum, a member of the same genus, these parts contain cyanogenic glycosides, especially dangerous when the leaves are wilting; signs of poisoning include brick-red mucous membranes, dilated pupils, difficulty breathing, panting, and shock. Keep pets from chewing on twigs and fallen leaves, and contact a veterinarian promptly if they swallow any.