Hi,

I think chill hours usually refer to fruit bearing trees that need a cold climate. But as far as Japanese maples are concerned as long as you live in the USDA hardiness zones specifically for Japanese maples you're fine. Some Japanese maples are more cold hardy and some are more heat/sun tolerant. You don't say what zone or location you're in. Here in Los Angeles we get winter temps below 45/50 degrees about 3 months out of the year and that's enough to get the trees to go dormant. Most, if not all the maples are rated down to zone 5. Some Japanese maples leaf out in early spring and are susceptible to late season frost damage on leaves and branches. If your maples are grown in containers you have special concerns with container damage and root freezing. You may need to overwinter your container maples in an unheated garage or basement and bring them out after the last frost.

Hope this helps,

Layne

Dianas is located in Florida. Though the term 'chill hours' is commonly used with fruit trees, most deciduous trees do need some sort of winter cold rest period to perform their best and to survive. Without it, some trees may last a year or more, but eventually weaken and not survive. I think Japanese maples are fairly flexible, however, as I have heard of some people just storing them in cold rooms for the winter.

Dianas, please see the attached post where there was some discussion on growing Japanese maples in FL.

Here is a link that might be useful: Japanese Maples in Florida