|Information from Bonsai Boon’s website
EARLY FALL WORK. (October)
This is an important month to continue fertilizing both deciduous and coniferous bonsai. The fertilizer that trees receive at this time of the year will help keep them strong through winter.
Deciduous trees: Reduce the amount of fertilizer deciduous trees receive when their leaves begin to change color. When most of the leaves have color, pull all of the leaves off the tree to give the weaker, interior buds more light in winter. Increased sunlight and air circulation will greatly intensify the strength with which the buds will open the following spring. For maples, pull the leaves forward with your finger or tweezers. Beech care differs slightly: use tweezers to pull the leaves backward to avoid breaking new buds. Do not wait for the dead leaves to drop off by themselves. Remove any remaining fertilizer after you remove the leaves.
Light pruning and wiring can be done after the leaves are removed. It is much easier to wire deciduous trees without leaves. But because new buds break off easily, wire your trees carefully. Do not wire trees that have gone completely dormant. This can lead to bleeding if you make a minor crack in a branch during styling. Wired trees need to be protected from freezing weather. If it is difficult for you to keep them protected, the options are to wait till late winter–early spring or wire them in later spring–early summer.
For deciduous and broad leaf evergreen bonsai use aluminum wire on smaller branches and copper wire wrapped (or larger size aluminum) with paper for larger branches. Aluminum wire is easier to apply and remove. Use copper for conifers.
Occasionally, some deciduous trees may sprout before spring arrives, especially if the region of the country where you live is subject to warm spells in winter. If this happens, just let the tree grow. New shoots can be cut off before repotting or before spring arrives.
Broadleaf evergreens: Old leaves will turn yellow and drop off. Pick off old leaves and clean the surface of the soil. Although late spring is the best time to work on broadleaf evergreens, it is okay to wire or lightly cut back broadleaf evergreens. Wait until spring to wire satsuki—the branches will be less brittle then.
Fall Wiring: Bonsai that is wired in fall needs protection from wind and cold. Bending may cause cracks in which ice can form. The expansion of ice in a small crack or fissure can damage live tissue and kill branches. If the temperature falls below 50° F, put the tree under an eve of the house or in an unheated greenhouse.
It is still too early to work on Japanese black pine the new growth is still too tender. Wait until November. By November, new needles will be hardened off. Keep more needles on the tree that you plan to wire. You will break some needles during wiring process. More needles will keep our trees stronger.
For you who live further north, it is almost time to put your trees in storage. The trees that receive some light during winter will grow stronger in spring.
For tropicals, this may be the last time to defoliate before the next growing season. Defoliate refined trees only. For trees in training, it is better to let them grow and then cut back in spring.
You can use a dormant spray in winter. It is best to do when the night temperature stay close to freezing. Use either lime-sulfur or copper spray.
Do not use dormant spray (lime-sulfur) on spruce, hemlock, azalea, tropical trees and recently wired trees. On these trees, lime-sulfur can penetrate open wounds and kill live tissue.
Suitable trees to work on this month:
- Japanese five needle pines
- Ponderosa pine, lodge pole pine and other high mountain pines
- Spruce and hemlock
- Cypress and false cypress
- Broad leaf evergreen
Note: It is too early to work on Japanese black pine and red pines. You should wait till at least in the middle of October. If your deciduous trees have changed to fall colors, then you can start working on them.