How to Storage Outdoor Bonsai in Winter

In many areas of the world bonsai require no special winter storage. Bonsai in warm areas remain outdoors during the winter, just as they do during the rest of the year. However, these bonsai do experience some degree of dormancy.

Great Place for Storage of Your Bonsai.


In cold areas that experience only occasional frost, trees should be grouped together and mulched with leaves, peat moss, or marsh hay. Mulch prevents evaporation of water from the soil and freezing of roots. Spread the mulch under and around the container, and also place one or two inches on top of the soil. Do not cover the foliage, as air circulation is important.

winter storage for outdoor bonsai
Outdoor Bonsai in Winter.
Image Source: mohawkhudsonbonsai.org

In areas with harsh winter, you must place your plants in some sort of winter storage, as in one of the following:
1. In an unheated basement or attic that remains cold and where the temperature does not fluctuate a great deal.

2. In an unheated greenhouse. Again, be certain that the temperature does not fluctuate. Greenhouse are usually built in the sun, so be sure to watch the temperature.

3. In the garage. Place the trees on a bed of mulch in a shallow tray with drainage holes. Fill in the area around the container with mulch and also place one or two inches of mulch on top of the soil.

4. In a cold frame, that is, an unheated, boxlike, plastic, or glass covered structure for protecting young plants. These structures are easily constructed, and various plans are available.

5. In the ground. Where it is possible, this is an excellent way to store trees in winter.

Prepare Your Bonsai Storage.

Prepare the spot before frost by digging a hole the shape of your container, and about two inches deeper and two inches wider than the container.
After a hard, killing freeze, place the tree on a two-inch bed of mulch, then place the mulch around the container and over the top of the soil.
Do not cover the foliage. Select an area where the foliage is free from drying winds and where snow does not slide off a roof, in other words, an area where the tree will remain cold and dormant.
A sunny spot can cause a thaw and freezing, neither of which is desirable. The purpose of storage and mulching is to keep the temperature constant.

An important advantage of outdoor storage is that trees do not have to be reintroduced to the elements. By being outdoors, dormant trees go into and come out of dormancy naturally, adjusting smoothly to changes of temperature and length of day. In contrast, trees coming out of garages, cold frame, etc., should be watched carefully. A sudden exposure to wind can cause the tips of branches to dry and die back.



All trees should go into winter storage with soil that is moist but not soaking wet. Water plants a day or two before placing them in storage. Throughout the winter, check the stored trees, and if they are dry, water them. Watering should be done in the morning so excess water will drain out during the day, before night falls. A long, unseasonable winter warm spell requires more frequent checking of stored trees’ water needs. They should return to total dormancy when the cold returns.

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