Not available – first paragraph follows: Most deciduous fruit and nut trees require a period of cold temperature below 45°F during the winter to induce dormancy and promote satisfactory fruit and shoot development in the spring. The length of cold period required, or chill requirement, has been established for most commercial fruit and nut varieties; values vary considerably among species. For example, most apple varieties require more than 1,000 chill hours; almonds generally need only 200 to 500.

The author thanks Ellen Gates, Statistician, and Richard Snyder, Bioclimatologist, both with UC Cooperative Extension, for their assistance.