Japanese persimmon bonsai

Placement

The Japanese persimmon is grown as an outdoor bonsai. As a deciduous tree, it needs a period of cold winter dormancy to stay healthy: do not keep it indoors. Give it plenty of light, ideally five to six hours of direct sun a day, especially in spring and summer, when it is actively growing; the more sun it gets, the more vigorous it is. On the hottest days, a little afternoon shade keeps the foliage from scorching.

In winter, it can stay outdoors year-round in mild climates, which correspond to USDA zones 7 to 9. It tolerates temperatures of about 21 °F; below that, protect the roots by insulating the pot or move the tree into a cold but frost-free shelter. In spring, keep an eye on the weather: late frosts damage the flowers, and an early fall freeze spoils fruit that is still green.

Persimmons most often carry male flowers and female flowers on separate trees, although some specimens carry both kinds. Only female trees bear fruit, but most cultivated varieties set fruit without pollination. A bonsai starts bearing fruit at around five to seven years old. For bonsai, the main species used are the American persimmon (Diospyros virginiana) and the Japanese persimmon (Diospyros kaki), which has the largest fruit: the latter is better suited to medium to large trees.

Soil mix

The Japanese persimmon needs a free-draining mix that holds a little moisture without becoming soggy. A mix of equal parts akadama, pumice and lava rock provides aeration, drainage and water retention all at once. A very free-draining mix of soil and coarse sand also gives good results. A substrate that stays wet encourages root rot and fungal diseases.

Watering

Water regularly throughout the growing season, from spring to fall, without ever following a fixed schedule. Check the moisture often: when the top layer of the substrate feels dry to the touch, water thoroughly until water runs out of the drainage holes. Let the substrate dry slightly between waterings and never leave the tree sitting in a full saucer. On the other hand, never let the root ball dry out completely. In winter, during dormancy, its needs drop considerably, but the substrate must not dry out entirely.

Fertilizer: from early spring, as growth restarts, and all summer long, apply a balanced slow-release fertilizer, or a liquid fertilizer at half strength every two weeks. Regular feeding also supports fruit production. Cut back and then stop in late fall and winter. Too much fertilizer produces weak, leggy shoots.

Pruning

Maintenance pruning is done during the growing season: cut new shoots back to two leaves while they are still tender, focusing on the top and the outside of the canopy, where growth is naturally strongest. In early spring, remove dead or damaged wood and cut back overly long shoots. The best time for structural pruning remains late fall, once the leaves and fruit have dropped: the framework of the tree is then perfectly readable.

Avoid large wounds: the Japanese persimmon heals poorly and slowly. Favor several small interventions over one severe cut, and cover every fresh branch cut with wound sealant.

As for fruit, too much exhausts the tree. In early summer, remove some of the young fruit: those that remain grow larger and take on a brighter color. As a bonsai, the Japanese persimmon often forms an elegant, slightly twisting trunk beneath a compact, balanced canopy; the informal upright and slanting styles show off its fissured bark nicely.

Wiring

The Japanese persimmon wires well, but its bark is fragile. As with most deciduous trees, wiring is easiest in late winter, when there are no leaves; you can also position branches from spring into summer. Anodized aluminum wire works well for deciduous trees. Choose a wire about one third the thickness of the branch, wound at roughly 45°, and protect the bark of thick branches with wet raffia before bending. Bend while pressing on the inside of the curve to reduce the risk of splitting. Remove the wire after a few months, before it marks the bark, cutting it off rather than unwinding it.

Young trees, whose branches are still supple, are much easier to shape: with age, the branches become brittle. So set most of the structure early, and limit yourself to touch-ups later on.

Repotting

Repot every two to three years depending on the age and size of the tree, in early spring, before growth begins. Prune the roots to keep a compact, vigorous system, without removing more than about a third of them, and adjust the amount of foliage to match the root reduction. Replace the substrate entirely so that it stays fresh and free-draining.

The Japanese persimmon is propagated from cuttings. It is fairly resistant to pests, but watch for aphids, spider mites and scale insects: washing with a soft brush or using insecticidal soap takes care of them. Leaves that yellow or drop too early often signal a watering problem or a fungal disease: check the drainage first.