Chill Hours? We Don't Need No Stinkin' Chill Hours!

I love old movies; and if they are filmed in black and white...all the better. One of the more memorable scenes in "filmdom" is from "Treasue of the Sierra Madre". Even if you've never seen the film, you likely know the lines from the scene in one form or another. They have become a part of our culture. Badges? We don't need no stinkin' badges! I often experience a similar attitude from would be gardeners to chill hours, but be careful they are more important than you realize.

Chill hours? We don't need no stinkin' chill hours! If you want to grow stone fruits, yes you do. For people in SoCal, a chill hour sounds like something you gladly left in your rear view mirror from Chicago, New York, Minnesota, or Ohio. The weather is awfully good here, isn't it? But, if you want to grow stone fruits a chill hour is something you need, and ought to become familiar with.

Simply stated a chill hour is an hour of temperatures below 45 degrees. When you shop for fruit trees, you will find required chill hours for a particular variety stated on the tag; typically anywhere from 100 to 1,000. The number given is the required amount of accumulated hours below 45 degrees the tree needs during its dormancy to bear fruit for the coming season.

There is also a caveat you need to be aware of regarding these little jewels called chill hours. It is the cumulative hours below 45 degrees without any periods above 75 degrees. Here is why that is important. Let's say you receive 3-4 frosty evenings in mid-November. You bank those chill hours. We receive a Santa Ana weather condition in late November, We all put on our "aloha" shirts and shorts and enjoy three days in the 80's. While you enjoyed those balmy days, you just kissed those previous accumulated chill hours below 45 good bye. The chill hour clock starts over again. The warm days essentially break the dormancy for the tree.

You can not get fruit from the trees you select unless they receive those necessary chill hours, so the varieties you choose will affect your home orchard success. All my fruit tree choices will be varieties you can grow anywhere in coastal southern California. If you live where you have frostier evenings, you have more choices; I will recommend varieties that can be grown from the beach to the mesas to the inland valleys with great success.

Be careful when buying from the big box stores or the club stores. I routinely find them ordering varieties requiring 750- 1,000 hours of chill. Don't guarantee your home orchard failure by purchasing a tree more suited to inland Washington state than coastal California. If you are a coastal wannabe orchardist, you need to stick to varieties that need 250 chill hours or less. But fear not, you can grow some truly amazing fruit within that magical temperature window.