The Ancient Art of Bonsai: Success With Indoor Bonsai.

Most tropical trees will be happy year round in the normal temperature range of a typical home, 60-90 degrees Fahrenheit. However, if you are trying to grow other than tropical trees, you likely will experience great difficulty unless you allow these trees to slow their growth down in the fall. Trees such as Cotoneaster, holly, elm, boxwood, pomegranate, Serissa, and azalea can be grown indoors, but many successful growers of these plants grow them in much cooler temperatures than exist in most homes.

To succeed with these plants try a cool basement, or a really cool window in an unheated, spare bedroom. Temperatures of 40-50F may permit some success with these species. Besides cooling down the growing area, another trick for success with these trees is to raise the humidity level. A humidifier can be placed near the plants or the plants can be surrounded with a plastic tent to increase the humidity. Leave the top of the tent open to keep fungal problems from developing. Cooler temperatures also help by keeping the relative humidity higher. Another technique to keep the humidity level up is to keep trays full of water near the trees but never allow the trees to sit in this water.