Documents: Special Interest: Bonsai:

Bonsai Basics
by Ruth Staal
September 9, 2007

Bonsai does not refer to a type of plant, but rather describes a method of pruning and shaping to create an illusion of a very old tree in miniature. A bonsai can be created from any plant which develops a woody trunk and tolerates pruning well. Bonsai can be loosely divided into tropical plants, deciduous shrubs and evergreens. There are several classifications, such as formal upright, informal upright, cascade and windswept.

The easiest bonsai to care for, if you are a beginner, is a tropical plant. A hibiscus, for example, grows well in our indoor living conditions, so will continue to do so after it is pruned, and repotted. Also suitable are azalea, natal plum, weeping fig, citrus, bougain- villea and boxwood.

Deciduous shrubs and trees need a cold, dormant period in the winter, just as they would if they were growing out-doors. Such trees as crabapple, birch, Siberian elm, cotoneaster, pygmy caragana and Amur maple can form attractive bonsai. During the winter they need to be kept in a cold but frost-free area but need very little light once they have lost their leaves. Close to but not touching a window in a cool room might be suitable. They cannot be kept outside in their pots above ground during the winter, as the soil temperature would change dramatically during our weather changes. A garage heated to just above freezing would be suitable, or the plant can be buried in the ground to just above the pot rim, then mulched well over the winter.

Evergreens are the most challenge. Because they need high humidity in the winter, and a temperature just above freezing, they cannot be grown successfully in your livingroom. They will tolerate a windowsill if close enough to the glass to be quite cool, (as long as the needles don't touch the glass if it is very cold outside), especially if curtains or a plastic sheet on the far side of the pot from the window keep warm air away from them and there is no hot air register under them. A tray larger than the pot filled with water, and topped with "egg crate" (used on flourescent lights) or strong metal screening will increase humidity. The pot sits on the screen and water can evaporate around it. An alternative is filling the tray with pebbles and sitting the pot on the pebbles, with the water level just below the top of the pebbles so that water cannot get into the pot through the drainage hole.

The amount of light a bonsai needs depends on the type of plant. A weeping fig, for example, needs bright, filtered light all year round, while a hibiscus would really prefer direct sun for twelve hours a day, every day, but will settle for the sunniest window you have, and only bloom when the day is long enough. Deciduous trees need no light when they have lost their leaves in the winter, and a bright, sunny spot when in leaf. When evergreens are cold in the winter, they are dormant and need no light, but need a good light when warm enough to grow. Many bonsai are grown under flourescent lights, usually using one cool white and one warm white bulb. The lights must be quite close to the plants, and the length of the 'day' depends on the type of plant.

Because bonsai are in small pots, with their roots confined, watering is critical. Soil mixtures should encourage good drainage, and will vary somewhat depending on the type of plant. Inserting a finger into the soil will tell you if the soil is damp, or dry enough to need watering. No bonsai soil should be covered with any material that prevents water from evaporating from the surface, or does not allow you to feel the soil. In hot weather, most bonsai will need checking for water daily, as once a plant dries out, the roots will likely not be able to absorb water and it could die. After many years of care, that can be devastating! Bonsai do not need a great deal of fertilizer, as we do not want to encourage rapid growth. The type of fertilizer used depends on the type of plant, but is generally a balanced one, such as 20-20-20, for deciduous trees or tropicals, and 30-10-10 for evergreens. Use half the recommended strength, or even less, and do not fertilize in the winter unless it is a tropical being grown under flourescent lights.

There are quite specific rules for pruning, wiring, etc. and many good books to help you. Don't be afraid to ask for help, and enjoy Bonsai !

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