Reference dates recorded are a statewide and varietal-wide average and should be calculated in your area to be more precise. Reference date is considered to be that date when 80 percent of the fruits sliced have hardened pits at the very tip plus 10 days.
Fruit Size Ranges (mm)
Full bloom is considered to be that stage of bloom where a few petals have begun to fall. Some years the bloom is sharp and easy to define whereas in borderline chilling years the bloom can be rather straggly.
Effects of Soil Conditions in Frost Protection
Soil conditions make a great deal of difference in frost protection. Heat is absorbed by the soil during the day and released to warm the blossoms at night and early in the morning. Maximum exposure of the soil to sunshine is necessary to provide optimum frost protection.
The following is a table of relative temperature differences as influenced by orchard floor conditions:
To adequately satisfy the chilling requirement for cling peaches (break the dormancy), approximately 800-1,000 total hours under 45ºF are needed. Chilling quality varies. The highest quality chilling for cling peaches would be in December-January temperatures of 28-34ºF at night and a daytime temperature in the 30s-40s. Warm, sunny days in January or December can cancel out the benefits of optimum low temperature chilling. Such years with intermittent warm weather during the chilling period are indicated in the accompanying table.