How to Care for a Bonsai Tree in Winter
At the start of winter, allwhich are vulnerable to severe frost should have been taken inside the house or given some other form of protection from the cold weather. If you don’t have anywhere to put such delicate plants, you could make a temporary frame out of wooden or metal and cover it with a lid of transparent plastic (such as polythene sheeting). The lid will give you the advantage of removing it easily or open it as soon as the temperature increases, and then the plants will benefit not only from the sunlight, but the ventilation as well.
You can continue to wire coniferto shape them during the winter.
Watering should be infrequent at this time of year, almost to the extent that it has ceased. This limits the risk of the, and obviously therefore the roots also, freezing if there are any unforeseen early cold bouts of weather. Fertilizer is really of no use in winter, as the bonsai plant lies dormant and doesn’t need any nutrients.
Mid-to Late Winter
The first severe cold spells are likely in mid-winter and with them the danger of frost. Their effects will depend on the force and direction of the wind and the nature of one’s trees.
A wet and dry thermometer can provide a fairly accurate frost forecast, though keeping informed via the media, particularly television. Probably provides a more reliable fore-cast as the satellite charts can be followed.
Bonsai trees kept outdoors should not be watered when it is severely cold as a moist root ball can freeze as soon as the temperature drops below 0°C (32°F). The small amount of compost in the bonsai tray, puts trees at risk from frost that would not be if grown normally. But this does not mean that a bonsai will always die if it is slightly frozen.
However, if the temperature drops below – 5°C (23°F), all trees at risk from freezing should be protected or brought indoors. If the trees are kept indoors during the winter, take steps to ensure that the ambient temperature does not exceed 5°C (41°F). All plants must be sprayed with water regularly. Their root balls can be protected by putting the trees side by side in a large box and covering their root balls with peat, making sure that they are well drained to reduce the risk of fungal diseases. If it snows, you must remove any snow from the branches at once, to prevent them being broken or deformed, thereby cancelling out the benefits of wiring.
Take particular care to protect bonsai trees kept close beside your house from the risk of snow falling from the roof during a thaw and causing them damage. On the other hand, watch that the trees do not receive too much winter sun, which can stimulate early buds which could then be damaged by late frosts. Premature budding can also upset the sap circulation, as the roots are still in very cold soil. Fertilizers should not be used during the winter while plants are dormant. Manure would either be completely ineffective during this dormant period, or even harmful during a sudden bout of warm weather, giving rise to premature budding.
Watering should only be done when strictly necessary assoil freezes easily.
Winter is a good time for preventive treatment against fungal diseases and pests whose eggs and larvae spend the winter under the bark.
It is also a good time to choose a deciduous tree, since, bare of leaves, its shape is clear and defects easy to spot.
Late winter is a good time to prune all plants which must be shaped before they make new growth. However, do not touch spring flowering shrubs.