On 27 Oct 05 at 17:23, Lee Poulsen wrote: > ...I have to hand it to the USDA for thinking of the single > best parameter to use in creating the first Zone map and then > making the map and seeing what the result was. The USDA zones were devised strictly, solely to gauge hardiness of woody material: trees and shrubs. That's all. They simply aren't applicable to other categories. IIRC, they were invented at the Arnold Arboretum. Presumably they work not too badly for their intended purpose -- in eastern North America, that is! In particular, the hardiness of bulbs and perennials depends on many other factors than just winter lows. And the hardiness zones are of very dubious worth in other parts of the planet. They only keep going because Joe Sixpack likes things reduced to a single number, no matter how misleading it may be. -- Rodger Whitlock Victoria, British Columbia, Canada Maritime Zone 8, a cool Mediterranean climate on beautiful Vancouver Island