Japanese Style House Plants: Indoor Bonsai
Traditionally, a bonsai tree is an outdoor plant, however, quite recently, efforts have been made to find species and cultivars that will thrive in the confined atmosphere of the home. Most indoor bonsai are, in fact, of tropical origin, trained to create the traditional shapes of outdoor bonsai.
Choose plants which become woody enough to be treated as bonsai.
While taking the origins of the plant into account, stand it in a well-lit place. Since lack of light is one of the most frequent causes of failure.
These plants need to be warm by day (about 15°C/60°F), but cooler by night. It is vital to recreate the humid conditions of their regions of origin, which are far from likely in winter in our often dry and overheated homes. It is essential to spray the leaves generously and often. With some bonsai it could be beneficial to stand the container on a tray filled with moist gravel to keep the air around it humid all the time. But never stand your bonsai container in a saucer or tray filled with water, as this could rot its roots.
For a large bonsai collection, the perfect solution is a heated greenhouse equipped with a sprinkler system, able to keep an ideal level of humidity.
Care of indoor bonsai
Apart from needing the best possible growing conditions (such as good light in a warm, draught-free position away from direct heat), indoor bonsai need quite different attention from their outdoor cousins.
Most require repotting every two years, preferably in spring. They can be potted at other times of the year, but it is best to provide some bottom heat to encourage re-rooting. Repotting should be accompanied by root (1/3 to 2/3, depending on growth). As with outdoor bonsai, try and stick to the same shape container, but of larger size. The drain- age holes should be big enough to prevent any waterlogging which could cause .
Do not use organic fertilizers as for outdoor bonsai, but use liquid fertilizers like those recommended for ordinary houseplants. Because bonsai containers are shallower than normal indoor plant pots, dilute the fertilizer further to avoid any risk of concentrated liquid damaging the roots.
Feed indoor bonsai with fertilizer in small, frequent doses (about once every three weeks), but do not feed in winter, unless the tree is being kept warm and is still growing vigorously.
Pruning and pinching
Shoots and leaves should be pruned and pinched back throughout the growing season, as soon as the shoots become too large. In some cases, such as with ficus, all the leaves should be cut back. However, the latter should only be carried out in late spring.
Wiring is nearly always necessary to train indoor bonsai. The method is similar to that used for outdoor bonsai, but the wires should be removed every three to six months at most. However, there are some indoor bonsai, like bamboo. That cannot be wired.
Ficus are a particularly suitable type of tree for growing over rocks with their roots exposed. They are planted over the chosen rock in exactly the same way as an outdoor tree such as a trident maple. In time, you will find that the roots thicken and intertwine, growing to form attractive interwoven patterns.
How to Care for Indoor Bonsai Trees
The seasonal cycle of growth of indoor bonsai is very different from that of outdoor bonsai, since there are no seasonal variations in climate. But this is not to say that the plant itself has no seasonal cycle. It is governed by its own biological rhythms, rather than by environmental factors.
Although watering should continue for most of the year (tropical plants not being used to any dry season), fertilizer should not be given in winter.
Pruning for shape should be carried out in early spring, with leaves (of the ficus species, for example) being cut back as spring ends. Wiring can be undertaken all year round, but be sure not to leave wires in position for more than three to six months without removing and adjusting them.
Repotting should take place in spring every second year. The roots should be pruned at the same time and the proportions of the root ball corrected.