Bonsai care in winter is a serious concern. All container plants need special consideration during winter - bonsai are no exception.
There are many techniques to keep your bonsai safe. Where you live will make a big difference.
While traveling to give bonsai programs, I saw many resolutions to the winter problem, amazing 'plant pits', cold houses, greenhouses and half-in-the-ground preparations.
I have discovered many good articles on the subject and my suggested reading is Harry Harrington's excellent article .
Harry is a well know British bonsai artist. These are silhouettes of some of his bonsai under the snow in England.
Are you growing tropical bonsai plants outside of a warm climate? When there is a "light frost" warning, the plant blankets may work.
Most hobbyists grow tropical bonsai outdoors in late spring through the summer and bring them indoors for the winter. See the page on growing bonsai trees indoors. If you have the space, a small greenhouse may be ideal.
If you live in the tropics, snow is not likely to be a problem. However, bonsai care in winter does include watching the weather for frost and freeze sneak attacks that occur primarily in the sub-tropics. (Such as Florida.)
When I lived In South Florida there were rare freezes. The farms and nurseries (including mine) ran the irrigation systems all night to keep the plants from freezing solid. As counter-intuitive as it seems, the ice protected the plants. No matter how cold it got, the plants never went below 32 degrees F
When the cold heads into tropical and subtropical regions, even a light frost for some tropical plants can be devastating.
Growers often use 'plant blankets' (as shown here) for frost threats.
This lightweight fabric can add 2-8 degrees to the temperature, depending upon the type you use. I particularly like the type that comes in a roll, it's easy to cut to size.
If your tropical bonsai collection is small and you can carry them, bring them indoors for the best protection! A night or two indoors is much better than risking a bad frost or solid freeze.
Covering your trees with plastic can help. HOWEVER, when using any type of plastic, always protect your trees with a layer of cloth or even newspaper between the plastic cover and your bonsai tree.
(This also applies to small yard trees and shrubs.) Plastic conducts cold and direct contact can cause damage. Also, remember to remove plastic when the temperature rises.
general Bonsai Care page
is my free monthly newsletter. Subscribe to get current tips, ideas and photos that may not appear on this site.