The month of January is, in many regions, the coldest of the year. Bonsai trees must therefore be stored away from frost, especially at night, and even by some hailstorms that could literally destroy the work of years. The plants without leaves (deciduous) can also be stored in the dark (a cellar, for example) in the period most at risk of frost, even if not for a long time.
Plants in general do not need excessive watering, just make sure the soil is sufficiently moist and then let it dry before a new watering; water should be administered during the hottest hours of the day, to prevent the roots from freezing. Be careful, especially in the South, to plants placed in greenhouses because one or more clear days could raise the temperature rapidly during the hours of sunshine, drying the soil.
PRUNING AND WIRING
Drastic prunings are indicated in this period for many flowering trees such as Lagerstroemia, Pomegranate, Hibiscus. Do not prune Willow instead in the period of intense cold.
Do not fertilize outdoor bonsai in this period. Indoor bonsai (up to one time per month) can be fertilized very gently, such as, for example, Pepper tree and Carmona.
It’s time to carry out preventive pesticide treatments using an oil-based insecticide to kill any eggs or larvae present in the plant. Wait for a dry period and perform the treatment against the wintering parasites and their eggs, integrated with an anticryptogamic treatment at high doses against the pathogenic fungi.
You can take advantage of this period to carry out the jobs that would take away valuable time in spring (cleaning of old vases, maintenance of tools, catalogs and books consultation, new purchases …) The works of this period on bonsai focus on spinning (you can apply the thread in Conifers from October to March) and on cleaning the vase. Other interventions are to be avoided, especially repotting and pruning, which could cause a shock to the plant even bringing it to death. A racking in this period can involve the freezing of the roots, while pruning could lead to a lymphatic withdrawal leading to the loss of branches.