Gardening editorial director Stephen Orr shares his tips on caring for bonsai.
What Is Bonsai?
Everyone seems to know a bonsai when they see it, but it isn’t always that simple. The term bonsai translates as "tree in a pot" in Japanese. In the West, the word is used to describe virtually all miniature container trees, whether they are trained bonsai or merely small rooted cuttings that have not been manipulated, pruned and trained to be bonsai. The term should be reserved for trees or shrubs that are grown in shallow containers, following the venerable principles of bonsai pruning and training developed over thousands of years in China and Japan. The result is a miniature replica of a full-grown tree that celebrates the effects of time, wind, and weather found in nature.
Some people sell plants claiming to be bonsai in malls, grocery stores and street fairs. These are usually young rooted juniper cuttings sold as houseplants. These junipers are outdoor plants and will not survive for long in most modern homes where the temperatures are too high and the air too dry.
Think of bonsai in two groups: indoor and outdoor. The latter type -- primarily found in the Northern Hemisphere -- includes pine, cedar, ginkgo, Japanese maple, hornbeam and juniper. These plants thrive on sun, fresh air and moisture. Many require a cool dormant period, and if deciduous, like Japanese maple, lose their leaves in winter. Indoor bonsai -- tropical and subtropical plants like ficus, Ming aralia, podocarpus and dwarf jade plants -- are easier to care for indoors. They require about the same treatment as ordinary houseplants, with one exception: they need to be watered more often, since they live in shallow pots without much soil. These are not plants that work for the frequent traveler. Having a bonsai is a little like having a pet. You’ll need a bonsai sitter if you’re away for more than a weekend.
Hardy outdoor bonsai such as junipers need to be grown over the winter in a protected environment. Some bonsai experts put their prized specimens in a greenhouse or sunroom that doesn’t get any warmer than about 55 degrees; others use a sunny part of a garage or outdoor cold frames. Some enthusiasts even bury the larger specimens in the ground, up to the rim of the pot, and cover them with mulch until spring.
The art of bonsai is to produce a miniature representation of a mature tree. A younger has branches that reach upwards towards the sun. As the branches grow, they bend lower and lower. By this careful observation, a bonsai artist can make a young tree look older just by wiring down its branches.
Bonsai trees have many shapes -- round, pyramid, columnar, mushroom, broom or inverted cone -- but most trees fall into these stylistic categories that define their form and the arrangement of their branches.
- Formal Upright
- Informal Upright
- Group Planting
How To Grow
The most common cause of failure with a new bonsai is improper watering. Conditions such as humidity, soil moisture retention, weather conditions, and size of pot all influence how often a plant should be watered. Bonsai usually need to be watered every day or two, but never left sitting in water.
Fertilize according to what kind of plant you are growing. A water-soluble fertilizer is usually applied every 2 to 4 weeks during the growing season, in a half-strength solution. Apply fertilizer only after you’ve watered the plant so that you don't burn the roots.
Bonsai usually need repotting every two or three years. This depends on the growth of the tree and also on the size of the pot. This should be done in the early spring. Do not fertilize for 3-4 weeks after repotting.
It is absolutely necessary to keep a bonsai trimmed and pruned so that it stays small. Remove the most vigorous growth in the spring, but never remove all the new growth at one time or it will weaken the plant. As you prune the top, you must also trim the roots so that they stay in balance with the reduced growth of the stem and branches. Wire the branches to achieve the proper look for the style that you are interested in pursuing. Remove the wire after six months so that the branch won’t grow around the constricting metal. Trim branches to expose the trunk and to shape the tree.