More bonsai are lost due to improper watering than from all other causes combined. The length of time between watering can vary quite a bit depending on conditions such as humidity, soil moisture retention, weather conditions, and size of pot. Bonsai usually need to be watered every day or two. The best time to water is early in the day or late in the afternoon at the same time every day. A thorough watering is accomplished when excess water runs out of the drainage holes in the bottom of the pot, BUT...too much water can be just as bad as too little water. In general, the soil should be moist, not soaking wet, and not dry.
Feedings vary from plant to plant (such as flowering plants have different requirements than the junipers). A water-soluble fertilizer is usually applied every 2 to 4 weeks during the growing season, in a half-strength solution. Miracle-Gro or Miracid are commonly used, but check label directions for your tree. DO NOT FEED right after repotting (wait for 3-4weeks). Don't feed if the tree is in a sickened condition. Premoisten the plant soil first. Never fertilize a very dry bonsai.
A bonsai must periodically be repotted to supply a pot-bound root system with fresh soil. It is also necessary to keep the root system in balance with the top growth. Most require 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. Do not let the roots go dry while repotting. Water well when finished.
A bonsai is nothing more than a miniature version of a normal plant, therefore it can be treated with commonly found insecticides and fungicides according to directions on the package. Insects such as aphids, spider mites, scale, and root aphids are common problems corrected by sprays, soapy rinse, or a systemic.
Trimming and pruning are the means by which a bonsai is kept miniature. This involves the systematic removal of vigorous growth in the spring. It is important however, to understand that for the health of the tree one should never remove all the new growth at one time. The roots are trimmed and so is the foliage on the plant. The tree is wired to assist in getting branches to grow in a specific position and to enhance the look of the tree. The wire is removed after 6 months. Usually the branch should then stay in that position on its own. Wire should be carefully cut from the branches. Do not unwind wires a s this could break the branch. Trim branches to expose the trunk and to shape the tree into the look you want. Two goals in bonsai are to make young trees look older by thickening the trunk and the positioning of the branches, and to find enjoyment in nature.
There are many varieties of plants that do well as an indoor bonsai such as ficus, aralia, azalea norfolk pine, serissa, gardenia, or boxwood. Note that these are all woody-stemmed plants and can have their limbs wired to direct the growth. Tropical and subtropical varieties cannot tolerate temperatures below 40-50 degrees F. These plants can be left outside when the temperatures stay above this. Light inside the house should be by filtered sunlight from an east, south, or west window. Grow lights 12 hours a day work well. When the plant is kept outside during the summer, place in partial shade.
There is a wide choice of trees for outdoor bonsai. The winter dormant period is essential to the general good health of a bonsai. In northern climates, winter protection from freeze-drying winds is necessary. Trees should be kept in an unheated area. An unheated garage, shed, breezeway, or cold frame can provide this. Check with your bonsai club for other ways. Check the root system for moisture and water as necessary while in winter storage. Unless the root ball is frozen they will need to be watered every week or so. In the summer, water more often as weather conditions demand. Never let the tree go dry, but do not keep it soaked either. Some of the trees suitable for outdoor bonsai are junipers, maples, elms, pines, gingko, hawthorn, and flowering crab apple.
This introduction to the art of bonsai was written by Connie Todd and has been provided through the courtesy of the Iowa Bonsai Association, a non-profit organization devoted to the art and study of bonsai. The Iowa Bonsai Association provides its members with programs and workshops relating to bonsai and the horticultural species adaptable to this art. The Iowa Bonsai Association may be contacted by e-mail.