Temperature Watch: If the daytime temperature stays above 50°F, leave fertilizer on conifers and board leaf evergreen bonsai. These trees will benefit from feeding. But this is not the time to fertilize heavily on any tree. If the nights are cold, and day time temperature is below 45°F, trees go into dormancy. Deciduous trees will change color before the leaves fall off. Conifers change their leaf-color as well. Juniper's needle can change from green to yellowish or bronze. The needles of some spruces and pines needle will change from green to yellowish.

Removal of Foliage: After you have removed old leaves from deciduous trees, they can be wired. Aluminum wire may be appropriate. Copper wire can leave a dark stain on the light colored bark such as Japanese maple, trident maple, beech and hornbeam. Copper wire that is wrapped with paper or insulated can be used on these trees.

It is time to remove old needles on pine, as long as you don't need them for the show. On strong and full Japanese white pine, 2nd year or older needles can be removed by cutting with scissors. On weak pines, remove brown needles only. Light thinning can also be done after removal of old needles.
Before you pull needles from your black pine this year, make sure that the new growth has hardened. Removed only the old needles. On stronger areas, like the top of the tree, some new needles may also be removed. Summer growth can be thinned out to 2 buds.

Cut back can be done at this time also. (This does not apply to your show trees.) If you plan to wire your tree, leave more needles. When you wire you might break some needles, so extra few pairs of needle should be left on the tree.

Clean Up: After old foliage removal is done, topsoil should be replace. Scrape top ½ to 1 inch of topsoil away from the trunk. Working from the base of the tree to the edge of the pot. Be careful not to create a dish or make it uneven. Small crossing roots should be cut. (Large roots can be removed when the bonsai is repotted.) Small roots that grow upward should be cut off. Brush off the old topsoil with small broom or brush. Add new topsoil and tap it down with small trowel. The soil level should be below the lips of the pot at least ¼ inch. Water it well afterward. This process aerates the soil and helps drainage. Compact topsoil can repel water, or stay too wet.

Dormant Spray: After trees are dormant, spray them with lime-sulfur-dormant spray. Lime-sulfur will kill insect-eggs fungus, and scales. Check the label for direction. (Generally, the recommended doze is 1 part lime-sulfur to 20 parts water). Cover the soil and pot with wet newspaper before spraying lime-sulfur. Lime-sulfur can burn the root of your bonsai. Water the soil after spraying to wash out excess amount of lime-sulfur.

Caution: Do not spray when, bonsai has just been wired, or the bonsai that will be shown in January, or when it is start to get warm. It can burn the tree and kill some branches.

Watering: Keep your eye on watering. Lack of water is as dangerous as too much water. Rain may not reach the soil. After light rain (or even heavy rain) you still need to check how much water your trees get. If the soil is soaking wet for long period of time, raise one side of the pot with a wood block. This will allow the water will run off to one side and the soil will stay slightly drier. Do not let the bonsai go completely dry. Root needs moisture to stay alive and healthy.