However, if you live in a temperate zone where winters can hit and stay at or below freezing, you need to devise a method of allowing your bonsai their natural dormancy and protect them from freezing.
- Mulch – Use a mulch that covers the lower first or second branches of your tree. In addition, placing your bonsai under any structure that protects it from heavy icing and dry winds but allows moisture is also recommended. If you must water, do it earlier in the day and only when temperatures warm to 45-50 degrees. Rule of thumb is: if the rootball is solid, don’t water – if it’s loose, water sparingly.
- Unheated greenhouse (or the equivalent) – Make certain that if there’s the possibility that the temperature can hit below freezing, use a small heater to sustain a moderately cool but not freezing temperature. If you opt for this method, don’t bring you bonsai in and then put them outside again on a warmer day. Consistency is important during dormancy.
- Cold Frame – Make a cold frame, outside, that’s raised, allows for light (but, not direct sun) and which can be opened, from time to time, to aerate your dormant bonsai.
Whatever method you choose, putting your bonsai into protection before the first freeze is your first best step to successful wintering over. Conversing, taking your tree out of protection too soon in the Spring can have the same affect. Wait a bit longer to make certain all chance of freezing and frost have past before introducing your bonsai back to a shaded, outside spot.
A moderate schedule of 0-10-10 fertilizer can be used to add strength to new growth and help bring your bonsai into a new season.