PLANTING AND CARE
Rather specific cultural practices have evolved for dwarfing hardy garden plants, trees, and shrubs, and growing them in small containers. Tender house and greenhouse plants, dwarfed and grown as indoor bonsai, are also potted, pruned, trained, and watered as outlined in this chapter. Otherwise, they are grown like the window-garden plants in Chapter 1.
Root-pruning
This is often the first thing you do for a plant that is to be grown bonsai-style. It is a procedure that is repeated regularly if your plant is to have a long life. Dwarf trees and shrubs are root-pruned so they will fit their small containers, or to make room for fresh soil when they are repotted, or to keep the root system in balance with the growth above soil that is being restricted. Pruning also keeps the roots compact, near the surface of the soil, and vigorously young. Removing old, woody roots encourages the growth of fine new ones.
When seedlings, rooted cuttings, and small newly purchased or collected plants are made ready for their first bonsai containers, they are not immediately root-pruned in a severe sense. Any roots that are dead should be trimmed off and long taproots should be cut back at least one-third. Otherwise, it’s a matter of trimming off the root ball with as little disturbance as possible, just enough to fit the container.
After they have been established, plants are root-pruned when they are repotted. When roots are crowded and completely cover the soil in a close mesh, it’s time to repot and root-prune. For some plants this may come once in a year, for others once in five years.
Hold the base of the trunk in one hand—your left hand if you are a right-hander. Use a dull-pointed pencil (the Japanese use a chopstick) and loosen the soil around the outside. Pick away about one-third of it if the plant is established, somewhat more on younger plants. When you have finished, the soil ball should be, roughly speaking, one-fourth smaller than its container. Then, with sharp scissors, cut away all the loose root ends which you have removed from the soil. This is rather drastic surgery, although not like removing an arm and a leg of a gardener, because the plant or shrub has the happy faculty of growing new roots. However, it will need special care and protection until it is back on its feet again. Bonsai plants are root-pruned and returned to the same container year after year. None of this making each container one size larger each time the plant is moved into a new house. That’s for house plants per se.
Soil
Potting soil for dwarfed trees and shrubs is particularly important. There is so little of it in small containers. In general, it should provide good drainage and aeration while also holding a certain amount of moisture. On the specific side, soil contents and textures should vary to meet the individual plant’s needs.
If your plant happens to have been dug locally, take along a supply of local soil. If you happen to have purloined the plant from a neighbor’s woods, purloin a little soil. It’s no more of a sin to have stolen a sheep than half a sheep. In our neighborhood it is a standing joke about how many plants, flat paving stones, etc., we swipe from each other. If you have been honest enough to have bought your plant from a nursery, ask their advice on the soil. If they are not smart, although most of them are, get the reference book down off the shelf and find out whether the plant craves a mixture that is sandy, rich in humus, acid or alkaline, fine or coarse. You have a baby on your hands. Treat it right and it will award you with adulthood in bonsai. Neglect it and it will curl up and die. Mix your soil as you would a baby’s formula. Remember, babies cry when the formula is faulty; plants can’t. They silently pass away.