Satsuki azalea bonsai

Placement

Satsuki azalea is an evergreen shrub grown outdoors all year. Indoors, light is too weak and the air too dry: growth weakens and leaves drop. In spring and fall, give it full sun, which produces strong flower buds and short internodes. In summer, shade it during the hottest hours, for example with shade cloth once temperatures rise above about 84 °F. Turn the pot now and then for even growth.

While it is in bloom, shelter the tree from rain and hot sun: the flowers last longer, and keeping the foliage dry limits flower rot. A healthy, mature tree can take some frost, but protect it below 23 °F; prolonged exposure below about 28 °F can cause branch loss and trunk damage.

Pests are not common. In dry air, spider mites move in; black vine weevil eats the leaves and its grubs destroy the roots, which beneficial nematodes help control. Leaf miners and aphids feed on tender growth. Azalea leaf gall, encouraged by wet conditions and most frequent on cultivars with solid red or purple flowers, turns leaves and stems into thick, fleshy, pale green growths that turn white, then brown: cut them off as soon as you see them and protect the tree from excessive rain. Use only products labeled for rhododendrons, and never lime sulfur. The satsuki azalea plant profile covers the shrub’s hardiness in the ground and its toxicity.

Soil mix

Azalea needs an acidic, lime-free soil. Pure kanuma, a soft, acidic Japanese volcanic soil, is the standard choice: it suits the tree’s very fine roots. Choose particles of 0–0 in and handle it gently: once compacted, it lacks air and encourages root rot. Soil that is not acidic enough leads to weak growth and yellowing leaves.

Watering

The root ball must never dry out, yet it cannot take constant wetness: overwatering is the most common cause of death in azaleas. Check the soil every day and water as soon as the surface begins to dry, sometimes once or twice a day for small pots in warm weather. The fine roots sit mainly in the upper third of the pot: alternate a light watering of the surface with a thorough one, until water runs out of the bottom. A root ball that has dried out can be rewetted by dunking it in a bowl of water.

Hard tap water slowly raises the pH: use rainwater, a mix of rainwater and tap water, or filtered water.

Fertilizer: during the growing season, use a fertilizer made for azaleas, either liquid every week or a solid organic feed at longer intervals, in moderate amounts. While the tree is in bloom, stop or halve the dose. Too much nitrogen favors leaves over flowers, and excess organic fertilizer clogs the soil and can lead to root rot.

Pruning

Azalea is one of the few basally dominant species: the lower branches grow more strongly than the top. Prune the lower part harder than the apex. The tree’s health also depends on the root zone directly beneath the trunk: if it declines, the apex weakens.

• After flowering: remove spent flowers and seed pods, then do the year’s pruning, because next year’s buds form in summer. Cut each tip back to two shoots with two leaves each. Pruned too late, the azalea will bear few or no flowers the following year.
• Hard pruning: it often regrows from branches with no leaves left, but cut into bare old wood only when necessary. Major styling work is done in spring, sacrificing that year’s flowers.
• Suckers: those on the trunk or at the base of branches can be removed at any time.
• Winter: thin out the summer’s shoots and any excess buds.

Styles: satsuki azalea suits slanting, cascade, clump (several trunks fused together), root-over-rock and exposed-root styles, from small shohin to large specimens. It does well in shallow pots.

Propagation: cuttings in spring and summer, under a clear cover in hot weather; this is the usual way to keep a cultivar’s flowers. Air layering also works.

Wiring

Azalea wood is brittle, especially with age: wire and bend with great care. Wiring works best on young trees in development; avoid stressing an already refined tree. Wire from late fall to late winter, letting the soil dry slightly before bending, and never on a weak or freshly repotted tree. Use aluminum wire about one third the thickness of the branch, coiled at 45°, and wrap thick branches in damp raffia. For a branch that is too stiff, use a guy wire instead.

Branches set in a few months. Watch the wire through summer and remove it as soon as it marks the bark, cutting it at every turn.

Repotting

Repot every two or three years, in early spring before growth starts or right after flowering, never in winter. The roots are very fine and matted: untangle and trim them with great care, as they tear easily. Inspect the area beneath the trunk and cut away any dark, rotten patches. Brush the base of the trunk to remove algae and debris, then repot in fresh kanuma.

After repotting, the tree has fewer leaves and uses less water: keep the soil moist without soaking it, and wait a few weeks before feeding again.