by George Buehler

Scientific Name: Stewartia monadelpha
(Pronounced Stu ar' ti a mon a del' fa)
Common Name: Tall Stewartia
Family: Theaceae
USDA Hardiness zones: 6B through 8B

There are several varieties of Stewartia: Mountain, Silky, Korean, Japanese [pseudocamellia], Chinese and monadelpha. The Stewartia monadelpha is generally the only species used for bonsai since the others have leaves that would be way out of proportion for bonsai. This month's tree of the month (TOM) is the Stewartia monadelpha.

The Stewartia monadelpha is a native of Japan (not the same variety as the pseudocamellia) that is not routinely grown by bonsai nurseries. However, I had the opportunity of getting one from Brussel's a few years back when he was selling them.

During summer, it is not very showy tree and, in fact, has dark green leaves that are slightly large for bonsai use. There does not seem to be any leaf size reduction benefit with defoliation, even with repeated attempts. Flowers are very unobtrusive, often going unnoticed in the dense foliage. Flowering is irregular, sometimes skipping several years in a row. However, when it does flower during June, it normally is followed by small very hard seed pods. Each pod contains three to five seeds that I have yet to get to germinate. Fall leaf color is an orange to dull red that rapidly dries up, but usually hangs on the tree until it is exposed to a freezing temperature for several nights in a row.

New branches grow upward and are easily scarred with wire. If wiring must be done, use of raffia or wrapped wire is necessary. Horizontal wiring will often result in limb vigor loss and, sometimes, complete limb die back. Clip and grow techniques are essential for tree maintenance. I have found, when removing a branch, that it is best to cut back to about an inch beyond where you want the branch to end. The remaining inch will die back and can be removed the next season without any noticeable scars. When trimming a branch to direct a new path, the same procedure should be used (i.e. cut it to about an inch of the bud).

In reading the above description, the Stewartia does not sound like a species for bonsai. Although the Stewartia is quite ordinary during the growing season, it is a spectacular showcase in the winter with its cinnamon to orange colored bark and upward pointing buds (see picture). It also has a slightly exfoliating bark, probably better described as a slight pealing bark that occurs all summer.

Stewartia can grow in full sun but does better in partial shade. If it is set in full sun, the pot needs to be kept cool either by water cooling or setting the pot where it will receive shade during the hottest part of the day. If a Stewartia is placed in full sun, it may require watering more than once a day, so watch it carefully.

The Stewartia requires lots of water in the summer but does not like lime containing water; therefore it should be watered with rain water. (I have used normal city water since I had the tree, and see no adverse effects. I do treat it with a dilute solution of an acid type fertilizer routinely - biweekly.) Reduce water applications in the winter to only that required to maintain a slightly damp soil.

Repotting is required every two to four years using a soil mix containing a high (~25%) organic component, along with Kanuma (10 – 15%) and lava rock. Only the thickest, hardest roots should be removed during repotting. My tree fills the pot with a fine root mass every two years or so. The longest roots are trimmed back about 1/3 along with the thickest roots.

During the growing season, the tips of all shoots should be pinched out as soon as two full leaves have developed. Tip pinching should be continued throughout the growing season to develop ramification. Any inward growing shoots should be removed as soon as they develop. To show the orange colored trunk and branches, I try to keep the canopy slightly on the open side.

Stewartia should be fertilized bi-weekly throughout the summer with a balanced type fertilizer alternating with an acid type fertilizer – both full strength. In autumn, a nitrogen free (or low nitrogen) fertilizer should be used.

No pests or diseases seem to be a problem or at least I haven't encountered any yet.

The Stewartia monadelpha is a tree that I would highly recommend to all except the novice.