The chilling factor is an important consideration when you're choosing apple or stone fruit trees, such as peaches, prunes and apricots, for a Southern California garden. These trees need temperatures of under 45 degrees Fahrenheit (contrary to what many think, freezing temperatures are not necessary) for a certain length of time. A chill needn't occur all at once but can be intermittent. You would think that all plant life would be suspended at such temperatures, but actually this is when the buds for future fruit are forming.
Chilling requirements can vary within a species. For instance, some apples can grow only in extremely cold climates, while others get sufficient chilling in our mild climate. Among the newest for our area is the Gordon apple, which was discovered in Whittier. Then there are the Anna and Ein Shemer apples, which were developed in Israel (each of these two trees needs the other for good cross-pollination and fruit set). Before buying bare-root fruit trees, check the chilling requirement. Keep in mind that plants get more chilling on the north side of a house or wall--or even on a north slope. For more information on chilling and for descriptions of the various fruit trees, send for L. E. Cooke's Descriptive Sales Guide ($1.50, plus 50 cents for tax and postage), L. E. Cooke Co., 26333 Road 140, Visalia, Calif. 93277; or call (209) 732-9146.