The repotting season is here. Deciduous bonsai can be repotted anytime from now on, but afterward they must be protected from bright sunlight, windy weather, excessive rainfall and freezing temperatures. Maples and larches need to be repotted first because once they sprout new green leaves it is too late. As long as you can only see green bud tips, it is still OK. From late February through late March is also the best time to repot azalea and rhododendron bonsai (more about these below). Evergreen conifers can wait until March or early Apr11, when other trees have been done.

The cautions about wind, excessive rain and freezing temperatures are easier to remember if we talk a bit about plant physiology. Roots that have been trimmed during repotting cannot absorb enough water to support the tree until they begin to re-grow, so misting the foliage will help a plant a lot more than watering the roots. Bright sunlight will also stimulate a heavy need for water that the roots cannot deliver. Windy conditions will desiccate new foliage faster than the roots can absorb moisture to replace it. If the leaves wilt and the column of water between them and the roots separates, the bonsai is a goner. But the answer is not to keep the root system wet, because the roots need a balance of both moisture and fresh air drawn into the soil as the moisture drains through. Too much moisture and not enough air slows or stops the growth of new roots and more water than that just drowns them. Roots hardly grow at all until the Soil temperature is warmer than 50F. But even when the air temperature is still near freezing, warmer soil will stimulate them to start growing. The temperature on the ground or under a bonsai bench will usually be warm enough to stimulate some new root growth, and setting the tree in an unheated enclosure is even better. The tree can be moved to a sunnier location in about three weeks.

Roots absorb nutrients mostly from dissolved chemicals, which have a strong attraction to the water in the plant's roots. But newly forming roots are fragile. Fertilizing too soon may draw the
Water out of the roots rather than letting the roots draw nutrients in, and the plant will collapse. So remember, the best place for newly repotted trees is out of the wind, where the watering can be kept controlled, and the roots will be warm enough to start growing again.

The older way of repotting azalea bonsai was to wait until they bloom (April - June), but it is better to repot early in the year. This is true for both satsuki and tsutsuji. While It is true that they become semi-dormant during the blooming time, their recovery and resumption of growth Is severely retarded by the disturbance and trimming of roots at that time. Much better for the development of the bonsai is to feed it in February or very early March and then repot about 10 days later; just as the growth cycle is beginning. However if you do repot early, do not let the tree bloom the same year! Two to six weeks after repotting you must cut off the flower buds and cut back the leaf tips surrounding the buds, leaving only about 1/8" to 3/16" of the leaves connected to each branch tip. The plant will be stimulated to produce a large number of secondary shoots over the bare wood of the branches and the trunk. You can develop as much new ramification as you want and simply rub off any unneeded buds that develop. Seeing a tree bloom only every other year is not a great penalty to pay for getting a much better bonsai in a lot short time. This process will keep your bonsai from getting leggy and demanding a larger pot every year or two.

The azaleas with small narrow pointed leaves are most hardy and may be repotted just before March 1st. Those with wider but still pointed leaves are done between March 1st and 15th. Those with nearly round leaves should wait until later March to be repotted. Trees in the "Osakazuki” family need to wait until early April for all trimming, and then should be pruned rather lightly, leaving two leaves on each branch tip. Removal of all the flower buds every other year will stimulate more and healthier growth in these recalcitrant varieties. Trees In this family, besides the namesake, Include "Hakurei," "Chinzan," "Kagetsu," and all the "Kagetsu" varieties.