Whether your bonsai are growing in the garden or in a heated indoor room, winter is a time for them to rest. Most woody species require the cold to become completely dormant. Growth slows to a halt and deciduous trees shed their leaves while conifers harden up their soft shoots. This dormancy is necessary to protect them from freezing temperatures and thawing water.
Temperatures are lower in the winter, and the soil is also covered by a layer of snow which protects the roots from sudden temperature drops. It’s important to avoid moving the bonsai around during winter because doing so could disturb these delicate roots and potentially expose them to freezing temperatures. If you do move a tree during this period, make sure it is protected from wind as well.
The best place to store your bonsai during winter is a small greenhouse that can be kept at a consistent temperature. These are ideal for tropical and temperate species that don’t like to freeze. If you don’t have access to a greenhouse, a garage or a basement that stays below freezing is a good option as well.
When storing a bonsai in a protected environment, it’s essential to keep the soil moist but not wet. If the soil dries out, it could easily freeze and kill the root system. It’s a good idea to water the trees periodically throughout the winter to ensure they don’t dry out. However, watering must be done very sparingly because the plants don’t need much water during this dormant period.