Japanese junipers are easy to grow as bonsai trees. They can be shaped into almost any bonsai style. They are hardy and live long. In fact, in Japan, some of the juniper bonsai trees are two or more centuries old. They can be grown both indoors and outdoors. Japanese junipers are an excellent choice for experienced and beginner bonsai growers.
Japanese junipers should dry out in between waterings, but should not be allowed to become dry for extended periods. Test for moisture by putting a finger into the soil to a depth of up to one inch. If a rock is in the planter, put a finger beneath the rock to check for moisture. If the soil is dry, water.
Soak the bonsai tree in a sink or container for up to 10 minutes, then drain. Alternatively, pour water onto the soil from above. Be sure to water the plant thoroughly.
Fertilize Japanese juniper bonsai trees every two weeks during the growing season, which takes place from spring until fall. Ideally use an organic, mild liquid fertilizer such as seaweed or fish emulsion. If a chemical fertilizer must be used, dilute it so it is half strength. This prevents damaged roots. During the autumn, when growth is slower, use a fertilizer mix that does not contain nitrogen.
Japanese juniper bonsai plants thrive with morning sun and afternoon shade. A mix of sun and shade reduces the need to water as often. Japanese juniper bonsai trees can tolerate full sun, but may require daily watering. Juniper plants grown indoors need at least two hours of sunlight each day. Full sun encourages the Japanese juniper bonsai tree to have dense foliage; partial sun results in slower growth, but a beautiful, rich color.
The Japanese juniper bonsai tree can be pruned and trimmed with bonsai sheers. The tree should be pruned in the spring, and again in the autumn if buds form on the tips of the branches. Failure to remove the buds may result in a less polished appearance.
Prune the roots in the spring to keep the tree from becoming root bound. Remove the tree from the pot, carefully remove the soil, and trim off about one-third of the roots before returning the plant to the pot.
In the first six years, re-pot Japanese juniper bonsai trees every two years. Re-pot more mature trees every three to five years. The best times for re-potting are spring and fall, but junipers may be re-potted any time of year. Water thoroughly after re-potting and keep in the shade for a couple of months to give the roots a chance to grow.