California's January weather was exceptional in 2009. While many enjoyed the unseasonably warm days, farmers fretted about the impact on their crops. According to an article in today's Santa Rosa Press Democrat, horticulturists say some plants and trees are budding two weeks to a month earlier than usual.

“Spring is coming earlier and it has been doing that the last three or four years. But this year is astonishing,” the article quoted Bob Hornback, a garden educator and adviser to a Sebastopol farm.

Press-Democrat writer Meg McConahey also sought comment from UC Cooperative Extension farm advisor Paul Vossen. He told the reporter experts do not yet know whether the temperatures through the winter were cold enough to sufficiently chill certain fruit trees.

To achieve optimum spring bloom on fruit trees, flower buds must be exposed to a certain amount of winter chilling during their dormant period. This chilling requirement is measured as the accumulated number of hours below 45º F. Fruit tree's chilling needs vary widely depending on the type and variety of fruit. Some apples, for example, such as McIntosh and Rome Beauty, require more than 800 hours of winter chill. Stone fruit chill needs range from 150 to 900 hours.