Chill Hours

Chill Hours

Many fruits and nuts require a certain number of chill hours in order to produce. The UC Home Orchard website describes chilling as "the number of hours below 45°F, is an important climatic factor that influences bud break, fruit set, and fruit development." Their tree selection webpage has a section on chill which provides additional information and a range of required chill hours for different types of fruit.

It's difficult to know what chill hours to expect for any particular garden. Not only is the weather variable from year to year, but there isn't easily accessible historical data for many locations in Santa Clara County. Complicating the issue are different chilling models—refer to the UC Fruit & Nut Research Information Center page on About Chilling Hours,Units & Portions for more information.

UC maintains weather stations throughout California and provides access to chill hours. There is only one location in Santa Clara County with chill data, the weather station in Gilroy, and the climate is different in much of the rest of the county. However, there is also a weather station in Union City which may have more representative data for some. We're not aware of any other local public sources.

Alternately, ask neighbors about plant varieties that have been successful in your area. Or contact the Santa Clara Valley California Rare Fruit Growers to get recommendations (as well as additional information about chill hours from their members).
    • Related Articles

    • Insect Identification

      The Master Gardeners are happy to help with insect identification. In order for us to do so, please provide information about where the insect(s) were found, specifics about the size, and close-up photos, showing front/back/top/bottom views. However, ...
    • How Much to Water Fruit Trees

      When watering fruit trees, it's crucial to focus on the right amount of water per week rather than how long or often to water. A general guideline is to provide one gallon of water per square foot of tree per week during hot summer months, with ...