A bonsai must experience all the changes in seasons that they would have been subjected to in their natural environment. But, a bonsai has only limited growing medium and needs extra protection from wind, sun, animals, and wide temperature swings. Winds dry the trees. The sun burns. Animals can destroy bark and roots. Wide fluctuations in temperature are very harsh for all container grown plants. Even an evergreen will lose moisture through its needles throughout the winter. If the soil is frozen the evergreen has no way to replace the moisture that is lost. The result is dehydration and possible death of the tree.

There are many possible ways to take care of your trees during winter:

Place your trees in a cold frame. Bonsai are placed in the cold frame in November or early December - and left there for the rest of the winter. On warm winter days the cold frame is partially opened to keep the inside temperature from reaching above 60 degrees. You do not want high temperatures to force trees out of dormancy and into growth. Once a tree begins new growth there is no way to return it to dormancy.

Bury the trees in the ground. If you have only a few bonsai, and there is space in your garden, you can remove the bonsai from their container and set them in the ground for the winter. The area selected should be protected from wind.

Store your trees in your garage. Place your bonsai on shelves in the garage. Some members heat their garage to about 30 degrees - but I am not sure this is necessary. The advantage of garage storage is that the trees have good air circulation and therefore are less susceptible to disease. The disadvantage is that there is less moisture in the garage (than with the previous two methods) so the trees have to be carefully watched for signs of dryness. Water when the trees appear dry. I used this method last year and found that the few trees that were lost were from dryness.

Cover your trees with micro-foam. Recently a new material (micro-foam) has been developed that has been used successfully for over-wintering bonsai. To protect your trees stack them on the ground. Cover them with the micro-foam. Make certain that the plants are sealed tightly - no air leaks. The plastic coating prevents any moisture loss. The trees are enveloped in moisture and thus dehydration is prevented.

 

Make sure that your storage area has excellent drainage. Roots will die if exposed to wet conditions followed by freezing conditions. Before storing your trees for the winter some members dust the area around the bonsai containers (but not in the containers) with flowers of sulfur and tobacco dust to discourage bugs, fungus, and small animals. Additionally, the uses of a granular systemic insecticide and a granular fungicide (benomyl) will help keep your trees free from insects and disease throughout the winter.

The previous comments are primarily for hardy trees. Tropical trees require special attention. The most obvious difference is that tropical trees must be brought indoors when the temperature drops below 40 degrees and for some species (such as buttonwood) before the temperature drops below 50 degrees. If possible place tropical trees near a window facing south (but avoid directsunlight). Alternatively place your trees under florescent lights.

Most members have an insect problem with their tropicals. As winter progresses more and more flying insects appear. Last year I used a systemic insecticide when I brought the trees indoors. There was a substantial reduction in the insect population. This year I am applying the systemic in mid September. I will make another application when the trees are brought indoors.

In case your Bonsai addiction is not getting enough juice to keep you from suffering from withdrawal, here’s a few items you may wish to consider:

The Cox Arboretum Bonsai Society will have their Fall Show at the Wegerzyn Horticulural Center on Oct. 28-29. There is a lot of road construction in Dayton, so you may wish to get some directions before you wend your way north.

On Wednesday, Nov. 9, the CABS will feature Jose Cueto, a favorite around these parts.

For those of you more far-ranging, the 4th World Bonsai Convention will be held in Munich, Germany, May 31-June 4, 2001, at the Sheraton Congress Center. You can get additional information from the www.bonsai.org website. No word on whether there will be a yodeling or bratwurst-eating contest.