Russell, I raised the question because I would dearly love to order a large number of your unusual bulbs. But forty years of trying to grow hundreds of hardy bulbs have taught me that here, at the opposite corner of the nation from you, hardiness is seldom if ever a problem but inadequate winter chilling is. Most "Mediterranean" bulbs that are hardy enough to survive Massachusetts winters might bloom the first spring after planting, but afterwards they just fade away here. Mediterranean littoral species will thrive, but we cannot give Mediterranean bulbs from higher elevations enough winter to make them happy. We can succeed with Crocus goulimyi and C. imperatii and Leucojum aestivum but Crocus pulchellus and Leucojum vernum will not do. Over the years of wasting money, perhaps I have grown overly cautious of experimenting. I just wondered if you had a system which might take more into consideration some of the other factors that limit bulbs in our region. John C. MacGregor South Pasadena, CA USDA Zone 9 Sunset Zones 21/23 On Feb 14, 2010, at 8:12 PM, Russell Stafford, Odyssey Bulbs wrote: > Hi, John. It's a low-temperature limit, in many cases a conservative > guess, and mostly in response to customers who virtually demand some > quantification of cold-hardiness. Lots of plants that thrive in zone > 9 in California fail in zone 9 in the southeastern U.S., just as many > that flourish in zone 5 in Colorado perish in zone 5 in > Massachusetts. Combine the hardiness rating with information on a > bulb's native climate, and it's somewhat more useful. A species from > a Mediterranean climate will likely do well in coastal California; if > it has a zone 5 hardiness rating, it should also do well in a region > (such as the Great Basin) with cold winters and relatively dry > summers. It might be iffier in the far damper Midwest and Northeast, > however. The same goes for heat-tolerance ratings. The > cold-hardiness and heat-tolerance ratings for most plants will differ > markedly in different areas of the country, so an estimated hardiness > range is essentially worthless for many or most locations. Seasonal > patterns of temperature and rainfall in the plant's native region -- > this is by far the most useful information.