Tim, to stop WLD (Winter Leaf Drop), I would purchase two items. First is a heat source, such as a heat mat that has a means of regulating the heat, and second a soil thermometer. Throughout the winter keep the tree's root zone at least at 64F, which should keep the roots activity at a high enough level to supply the tree's foliage with ample moisture, and nutrition. If any further leaf drop is noticed raise the container's temperature to 70F, which will completely stop any leaf drop. Doing all of the above, will also produce good winter tree growth. An alternative, is to place a sheet between the tree's foliage and the sun, while letting the sun's ray's still shine on the container. However, this last method will not produce any new grown, from October to March. - Millet (1,034-)

since I keep my trees indoors during the winter months under a grow light, should I put the pots directly on a plant heating pad in attempts to keep the soil temperature above 70 degrees at all times? I tested this tree and and while under the light, the soil temp was at 71F. However, once the lights are off at night, I can only guess that the temperature would fall since the pots are on a tile floor now. Thanks for your help!

Actually, I think 64F would be high enough. If your light is close to the foliage of the tree, the leaf blade temperature could become quite high, requiring the roots to send up water so the foliage can cool. When you test for the temperature of the container test both near the center of the container and 1 inch inside the container's wall. You can also test at the depths of 1/2 way down and near the bottom of the container. If you heat mat has a thermostat, the mat will turn itself off when the required temperature is reached. Remember, if you don't care about winter growth, you might not even need to light the tree. - Millet (1,034-)