Chilling hours relate to the time a region is between a set of temperatures. Most authorities put this range as 32-45 degrees F, though this is a simplified definition. Central Pennsylvania for instance may have 1400 chilling hours in a given year. Much of Florida however, may get none. This is important because many temperate fruits require a certain number of chilling hours to grow properly, enter and emerge from dormancy, and to set fruit. A plant may survive in a miscalculated region, but not set fruit well of grow properly. Now, most of the US will have plenty of hours so most of us do need to be concerned with this issue. Those in the extreme south however will have be more mindful when choosing some fruits.
Chilling hours are generally not listed in the product pages of our website, but here are some helpful, though rough, guidelines:
Fruit Crop Chilling Hours Required
Currants and Gooseberry 800+
Northern nuts 800+
Raspberry (northern varieties) 700+