Native to China and Japan, the Japanese zelkova (Zelkova serrata) bonsai has leaves similar to American and English elms, only smaller. Though related to elms, the Japanese zelkova bonsai resists diseases common to elms. In the winter, the zelkova produces little green flowers with a gentle fragrance. Covered in smooth bark, the trunk of the zelkova goes from green to grey in color as it matures. Considered one of the best deciduous bonsai trees, the zelkova remains a popular choice among bonsai enthusiasts.
Position the Japanese zelkova bonsai tree on a sunny windowsill during winter months. Expose the tree to at least three hours of sunlight each day.
Move the tree outdoors after danger of frost subsides, but provide some shelter during the hottest summer months. Keep the tree outdoors until fall so the leaves drop off naturally before the tree is moved indoors.
Water the zelkova bonsai tree only when the soil feels dry to the touch. Water the plant by submerging the pot and the top of the soil into a sink or tub. Keep the plant in the water for 10 minutes.
Remove the plant from the sink or tub and allow it to drain. Water the Japanese zelkova bonsai more frequently during high temperatures and times of increased growth.
Feed the bonsai tree every week during the spring and summer months with an organic fertilizer made from fish emulsion or seaweed. Substitute chemical fertilizer if necessary, but use twice as much water as called for on the label instructions. Mix up as much fertilizer as needed to submerge the pot into the fertilizer mixture.
Reduce feedings to once a month in the winter. Withhold fertilizer from the zelkova bonsai tree when leaves are not on the tree. Feed the tree with fertilizer that has a high nitrogen and potassium content during the first month of spring.
Prune the zelkova bonsai tree in the spring and summer. Cut back shoots, leaving only one or two leaves on each shoot. Style the zelkova bonsai tree in any bonsai style except literati. Consider pruning in broom style because of its thick branches. Prune about one-third of the roots each time the tree is re-potted.
Re-pot the zelkova bonsai tree early in the spring and annually during the first few years. Re-pot trees that are more mature every two to three years, when the roots become tangled or if the tree outgrows the pot.