Chinese sweet plum bonsai

Placement

Sageretia thea does not cope well with frost. In the warm season it benefits from time outdoors as soon as nights stay above 41–43 °F: give it morning sun and afternoon shade, or light partial shade. It tolerates full sun, but then it drinks far more; if it is coming out of the house, get it used to direct light gradually to avoid scorch.

Bring it in before the first cold spells and overwinter it in a bright room or a heated sunroom, between 54 °F and 72 °F. Above 50 °F it keeps growing; below about 55 °F it readily drops some of its leaves. Set it by a bright south- or west-facing window, but shielded from afternoon sun through the glass. The warmer the room, the more light it needs: a grow light helps in winter. Avoid constant dry heat; a room that is cooler at night suits it better. It can also be kept indoors all year.

Humidity matters a great deal: stand the pot on a tray of damp gravel and mist the foliage often.

Soil mix

A basic bonsai mix suits it, as long as it holds enough water while still draining well. Some growers get better results by adding some organic matter, such as peat, mixed in equal parts with mineral ingredients like pumice. Choose a pot slightly larger than usual so the root ball dries out more slowly.

Watering

This is the trickiest part. The root ball should stay moist but never soggy, and above all it must never dry out completely: a single missed watering can be enough to kill a sageretia, and only a very healthy tree recovers from wilting. Check every day by pushing a wooden chopstick into the soil, and water as soon as it comes out nearly dry. In full sun, water needs rise sharply.

Use neutral to slightly acidic water, such as rainwater: hard water causes iron deficiency, which shows as pale green leaves with darker veins. Use lime-free water for misting too.

Fertilizer: during the growing season, apply a solid organic fertilizer every four weeks or a liquid fertilizer every week. In winter, give liquid fertilizer once a month if the tree is in a cool spot and every two weeks if it is in a warm one, always on moist soil. Sageretia is a heavy feeder; base how often you feed on the light it gets rather than on temperature.

Pruning

Sageretia is very easy to prune. Shoots can be cut back to two leaves at any time of year, and frequent trimming builds fine, dense branching. A vigorous tree buds back freely on old wood after heavier pruning. Still, let a young plant extend 4–6 in before cutting it back to help the trunk thicken: it fattens slowly, and thick-trunked trees are usually grown in the ground for years. On a more refined tree, pinch new shoots regularly to keep the outline.

Small yellowish-white flowers appear in clusters in late summer, followed by small dark blue berries. If you want to see them, stop trimming in late summer.

Styles: its angular habit and readiness to bud let it take every classical style and size.

Wiring

Sageretia is shaped mostly by clip-and-grow, and wire is rarely needed. If you use it, wire young, flexible shoots in spring: older branches turn stiff and hard to bend. Once the framework is set, there is almost no more wiring to do.

Use wire about one third the thickness of the shoot, wrapped at roughly 45° from base to tip. During the growing season the wood thickens fast and wire can mark it within one to four months: check it often and remove it by cutting it at every turn rather than unwinding it.

Repotting

Repot about every two years, in spring as the buds begin to swell, or as soon as the roots completely fill the pot. Sageretia tolerates root pruning well: remove a third of the roots at most. Use fresh mix and a pot large enough to slow drying. After repotting, keep the tree out of strong sun and wind, and above all do not let the root ball dry out while it recovers.

Propagation: softwood and hardwood cuttings root easily during the growing season, sometimes even in a glass of water within two to four weeks. Seeds need no cold period and germinate in any season.

Pests and diseases: under glass, watch for aphids and whiteflies; higher humidity helps keep them down. Mealybugs hide under the flaking bark: pick them off with tweezers. Spider mites appear in dry, stuffy air, and fungus gnats in soil that is always wet. Against powdery mildew, which is rare, improve air circulation rather than lowering humidity.