Chapter 131 Stewartia pseudocamellia

131.1 Japanese stewartia

Stewartia bonsai in the National Arboretum collection. Link to original image.

131.2 Soil: Ericaceous Mix

Ratio: 3 parts bark, 1 part peat, 1-2 parts grit

Add-ins: dolomitic limestone (MAX of 2 lbs/yd), Tree-Tone (15 lbs/yd)

pH: ~5.5-6.0 (acidic)

Moisture: consistently moist but well-drained. They prefer an acid soil that is rich in organic matter that is well drained but does hold moisture.

131.3 Light

Routine: full sun to part shade.

Summer: move to shade to keep the roots cool.

131.4 Cultivation Notes

131.4.1 Potting & Root Pruning

Schedule: will need repotting every 2 years because the roots grow rapidly to fill a pot. Repot before bud break. It has fine fibrous roots that are easily damaged.

131.4.1.1 Top & Branch Management

Multi-colored bark of a stewartia. Link to original image.

They respond well to pruning but can suffer branch die back if left exposed in winter so protection from hard frosts is essential. Prune smaller amounts more frequently, rather than remove large quantities all at once. Frequent but less aggressive pruning improves back budding and leaves a more even shape.

Heavy pruning: prune thick branches just before bud break.

Fine pruning: a Stewartia will keep on sprouting all season. Start trimming as soon as the tree has sprouted. Let branches grow free when they need thickening. Then cut back to 2-3 leaves. Pinch other branches regularly to maintain fine ramification.

Leaf pruning: to stimulate ramification on young trees, remove large leaves at the tips of the branches. Do NOT defoliate completely; they will not tolerate it.

Wiring: the bark is soft so avoid wiring unless necessary and ensure to check this often to avoid wire marks.

131.4.2 Feeding

Flower and foliage of stewartia. Link to original image.

Fertilize like azaleas or camellias. For trees in training, use soluble azalea food at full strength; reduce to half strength for trees near their final size, or in show pots. Stop fertilizing about a month before frost.

If feeding with an organic fertilizer, use one formulated for hollies or evergreens, like Epsoma Holly-Tone.

131.4.3 Pests & Problems

No serious insect or disease problems.

131.4.4 Winter Storage

Fall foliage of stewartia. Link to original image.

Site in a location sheltered from winter winds and mulch thoroughly to protect the roots from frost.

131.5 Propagation Notes

They can be propagated from seed, with difficulty. Stem cuttings and air layering can be done in May to June.

131.6 Artistic & Styling Notes

131.7 Additional Information

131.7.1 Natural History

Stewartias are native to the mountains of Japan and Korea. Specimens in the wild can reach 50-60’ tall, but in cultivation typically mature over time to 20-40’ tall with a slightly narrower canopy width. They can also be grown as a large, multi-stemmed shrub. They are hardy in Zones 5-8. White blooms appear from June to July. The fall color and flaky colored bark add year-round intrest.

131.7.2 In Cultivation

Trees are slow to establish and transplanting success is highest with young plants. Requires consistent moisture and is intolerant of drought. Partly shaded conditions are preferred in climates with hot, humid summers.