Seasonal Care and Maintenance
As the seasons change, the Bonsai grower must take into consideration the circumstances and dilemmas that might affect their plants. Because the trees aren’t in the ground, you need to do what you have to in order to insure your Bonsai survive the seasons.
In the summer, Bonsai Trees need cool nights, sunny days, and mist or rain almost daily. If your climate does not offer these conditions naturally, you must supply them artificially. Avoid any extremes in temperature, light, rain, and wind. Water the entire plant daily, but do not let them become water logged. One thing Bonsai Trees hate is sitting in wet soil.
In the Autumn, Bonsai Trees must be prepared for the winter. Slow the growth of the plants by watering less frequently and discontinuing fertiliser application. Do not prune or cut any branches after mid-August.
Winter's low temperatures and drying winds can easily kill Bonsai trees. If the winter temperature drops below 28F, Bonsai trees must be protected by a greenhouse, pit, or cold frame. A cold frame is basically a box that houses your bonsai through the winter months.
If you put them in a cold frame, don't forget to water them while inside. Winter watering may be only necessary every other day. More Bonsai trees are killed by over watering than by desiccation.
In the spring, start new Bonsai trees, prune the old ones, and continue training measures. The remaining part of the growing season is used for the plants' adjustments to these practices.
In general, Bonsai Trees are fine being outside in temperatures above 15F. Below this point, some kind of protection from freezing is needed. You can bring them inside, but this could jeopardise the plant’s health. In extreme circumstances, this may be your only option.
Just remember that woody plants must go through a period of cold dormancy to survive. If you do not give them this time, they will die.
Dormancy is a survival strategy that temperate climate species have evolved to stay alive over the winter. These species have a biological clock that tells them to slow activity and prepare soft tissues for an onslaught of freezing temperatures. Species that have well developed dormancy needs cannot be tricked out of them.
You can try placing a tarp or plastic film over your Bonsai Tree in cold temperatures. Do this at night and remove it during the day.
It is important to note, that the trees will not be able to withstand the warmer temperature once they have begun to grow. Just as trees became gradually ever more frost resistant in fall, they will get progressively less frost resistant in spring.
The closed buds, although swollen, will still be able to survive short periods of mild frosts, but once the buds have opened and the young leaves start to unfold, frost can cause serious damage, and trees should be returned to frost-free shelter when it threatens.
Also remember that full-size trees lose their leaves in the winter. Your Bonsai tree is a miniature version of a full-size tree and it, too, will lose its leaves. This is fine and normal. They will grow back!