Known for their gnarled and twisted branches, Japanese junipers are native to the rugged mountains of Japan. They make excellent bonsai trees. They are remarkably hardy and can live a very long time. In fact, many of the Japanese juniper bonsai trees in Japan are more than two centuries old. They are flexible and can be trained into almost any bonsai style. Japanese juniper trees do well both indoors and outdoors, as long as they receive enough sunlight. They should be kept in a cool room in the winter to simulate the winter season.
Expose the Japanese juniper bonsai to moderate light. Japanese juniper trees thrive in full sun in the morning and partial sun in the afternoon. Full sun all day long is tolerated, as long as the plant receives daily watering. Indoor juniper plants require at least two hours of sunlight each day.
Water thoroughly. The Japanese juniper requires thorough watering, but should dry out in between watering. Put your finger into the soil to check for moisture before watering. If the pot has a rock for decoration, test the soil beneath the rock. When the soil is dry, it is time to water.
Feed the bonsai with organic fertilizer every two weeks. Fish emulsion and seaweed fertilizers are both acceptable options. Chemical fertilizer diluted 50 percent works as well. The dilution keeps the roots from burning.
Prune during the spring and fall, when buds are present. Use garden clippers to remove or shorten branches. Use fingers to remove buds. Prune roots of the Japanese juniper bonsai tree in the spring to prevent root bound. To prune the roots, remove the tree from the planter, gently remove as much soil as possible, and trim about 1/3 off the length of the roots.
Repot the plant every two years during the first six years of its life. Repot more mature trees every three to five years. Repot in the spring and fall. Allow the plant to sit in the shade for several weeks after repotting so the roots have a chance to develop.