BONSAI is a form of “living” art. The bonsai “artist” shapes trees to give the appearance of aged, naturally dwarfed trees. The plant’s ultimate form may take many years to achieve using pruning, nipping and wiring.
The cultural requirements listed below are very basic. We recommend further reading both on the art of bonsai and on the care of specific plants.
Tropical and subtropical trees and shrubs make interesting and beautiful bonsai, and can live inside year round or summer outside. “Hardy” or temperate zone plants require a cold, winter dormancy period of several months with temperatures below 50ºF. To protect hardy bonsai from freezing during this time, the bonsai could be planted in the ground in a protected area, kept in an unheated garage (with a suitable light source for evergreens), or placed in a cold frame or cool greenhouse.
Light requirements vary by species, but most indoor bonsai will grow happily in an east or west window, where there is direct morning or late afternoon sun. A south-facing window is generally too hot. Lower-light tolerant plants can be grown in moderate to bright indirect light. Outdoor bonsai generally do best when shaded from the mid-day sun.
Too much or too little water can kill a plant quickly. Always feel the soil before you water, to determine its dryness. It is not a good idea to rely on a schedule for watering, as the plant’s water needs can change with temperature and light fluctuations. Some species need to be consistently moist (only dry on the surface), while others need to dry more between waterings.
Over-head watering should be done using a very fine spray or mist to avoid eroding the soil. This will also clean the leaves of dust and help prevent insect pests. Always water thoroughly, not just dampen the top of the soil.
Bottom watering—setting the bonsai in a saucer of water until an adequate amount of water has been taken up by the soil—avoids eroding the surface soil from the base of the plant. Always discard any water not absorbed by the plant within 15 to 30 minutes.
It is best to water early in the day, using day-old or rain water. Light misting of the foliage will aid in humidity and in keeping the foliage clean, and should also be done early in the day. For plants requiring higher humidity, use a pebble-tray (humidity tray). Set the bonsai on a saucer or tray wider than the bonsai container, fill the tray with small pebbles, and keep water just below the surface of the pebbles. As the water evaporates, it increases the humidity immediately around the plant.
A fertilizer with trace elements is recommended. Plants should be fertilized when they are actively growing (usually the spring and summer months). An average application rate would be every other week at one-quarter strength. Use a balanced formula product (e.g., 20-20-20 or 10-15-10)
Pruning will determine the shape of your tree, giving direction to new growth or removing dead branches or new tips that would distort the desired form. In addition to shaping your plant by pruning, you may wish to bend branches or trunks. These can then be wired to maintain the shape until the wood hardens in the desired position. We recommend bonsai books or other bonsai enthusiasts for information on styling your plant. Roots will also need to be pruned periodically (perhaps every two to three years), to make room for healthy new roots. Root pruning should be performed at the beginning of a growing season.
Keeping your bonsai in a healthy condition is the best preventative against disease and insects—this means good cultural care and an appropriate environment. If your bonsai does become infected, treat it with a product recommended for the specific disease or insect.
Note: National and local bonsai societies are great places to meet other enthusiasts and benefit from the experiences of others.