The Japanese Elm, also known as japonica or zelkova, is a member of the Elm family of trees, and is native to Japan, Taiwan, and South Korea. It is wide-spreading deciduous tree, with an umbrella like structure. It looks quite similar to the Chinese Elm and can be differentiated by the fact that the Chinese Elms have double-toothed leaves while the Japanese Elms have single-toothed leaves. It has a dark-grey smooth bark, pointed leaves, and a dense structure.
The tree can be seen around Japan as a street tree or in the parks and gardens. It first reached North America in 1895 as a seed. The tree prefers rich soil and a full sun. Its leaves turn lemon-yellow to a bright red during the autumn season. It is a fast growing tree and thus quite popular as a Bonsai.
When buying this tree, one should ascertain if it has been acclimatized indoors or outdoors, and plant the tree accordingly. If grown indoors, it turns out to be an evergreen tree while if grown outdoors, it grows to be a deciduous tree. The japonica grows best in a sandy loamy soil and needs to be placed in full sun during summers and kept inside during winters.
The tree should never be over-watered; however the soil should never be dry too. It should be watered as required, maybe twice a day when the weather is hot, and every alternate day in winters.
A balanced fertilizer, applied twice or thrice a month in spring and summer, works best for the tree. It is advisable to avoid fertilizing when the tree has shed leaves.
The tree responds well to pruning. It should be pruned during spring season, back to 2-3 leaves.
Initially, the Japanese Elm bonsai should be repotted every year as it grows very fast and the roots may go out of control. Once the tree is mature, it should be repotted less often.
The Japanese Elm has a soft bark and prolonged wiring must be avoided as it may leave marks on the bark.
The tree is highly resistant to the Dutch Elm disease and is used to develop hybrid disease resistant cultivars. However, it needs to be protected from aphids, leafhoppers, and mites.