| Good! I guessed right! The USDA and Arnold Arboretum hardiness zone systems were developed primarily to help farmers in the gentle climate gradients back East know when to plant their crops, or whether or not a particular variety of Azalea would freeze. They are based solely on winter lows, without any reckoning of summer highs, length of cold or hot periods, or rainfall and humidity. When you try to apply either of these two systems west of the Pecos, you get strange results: according to them, Phoenix, AZ is in the same zone as Tacoma, WA! Obviously two completely different gardening worlds! The Sunset Zone system was developed when Sunset Magazine published their Western Garden Book, probably in an attempt to go around the limitations of the USDA zones. It tries to include the missing factors in describing the actual gardening climate, and turns out to be a much better indicator of what will grow--and what won't--in a particular part of the West. Below is an address to a PDF of two maps of California: one of the USDA zones, and one of the Sunset zones. I noticed that in some areas the two zone 8's coincided. http://www.csgn.org/csysg_trainer/HO-Know Your Zone.pdf On the other hand, USDA zone 8 also mostly coincides with Sunset zone 11--the mid-elevation desert. That climate has summer soil temperatures similar to my area, which is going to limit perennializing some of the traditional northern bulbs, which Sunset zone 8 is much friendlier to. So you may be better off than I thought! Hope this helps.
Kevin : ) | 
