This is one of the busiest times of the year for those of us who grow and care for bonsai. The sun is lowering in the southern sky, the days are very short, the temperature is getting colder and things are generally wet. When this is combined with the wind and the conditions affecting your bonsai the care regime becomes increasingly complex. Here are a couple of hints:
Begin by looking closely at each bonsai and removing all of the spent leaves. See if you have scale insects living on your bonsai; they may seem dry and pop off pretty easily but they are overwintering and need to be removed. Check for biting wires if you have placed wire to style in the time frame from August till now. Check to see how fast your pot is draining. If it is slow mark the tree to be repotted this winter or early spring. Because we have so many trees we have begun our repotting already and will continue to do this until early April of next year.
Move your material into full sun, such as it is. Place a small object under one side of the pot so that it is tilted slightly; this will let the rainwater run off more quickly. Prepare all of your repotting materials (soil, wire, screen, work area, place to put old soil, ground pruners and branch pruners) and make sure all your tools are sharp and clean.
Black Pines can be cleaned up and styled from now on but should not be repotted until next spring when it begins to warm up. If you have White Pines they can be repotted from late December well into next spring. Junipers can be repotted once the days begin to warm up, usually March/April. Although it is not uncommon for us to experience a nice and warm week or two in December. Look closely at your Junipers if they seem to be getting a grey or washed out looking. This can often be a result of mites. Treat with oil and a systemic pesticide. Pines and Junipers can be lightly pruned (cutting of small branches and shoots) and wired from now on. Do not make large cuts until Spring because major open wounds invite bad things to crawl into your bonsai. Make sure that if you need to make larger cuts (1/4″-3/8″ branch) that they are very clean and sealed up good with cut paste or latex paint.