I was told that "all supermarket garlic now comes from China and is average at best".
Some vendors do sell heirloom garlic bulbs, some of those organic:
http://www.rareseeds.com/store...
http://www.territorialseed.com...
That garden calendar based on USDA Hardiness zone totally confuses me! The USDA Zone is only the average of HOW cold it got in each of the last 20 winters. Not WHEN. USDA Hardiness zone has little to do with your first frost date! I think their table that shows a first and last frost date as a function of Hardiness zone is pretty bogus.
I tried my ZIP code there, and they said: "arborday.org hardiness zones: 8 - 9". Pretty vague.
I haven't researched it, so I might be confident-and-quite-wrong.
Dave's calendar DOES look up first and last frost date for each ZIP code, not just the Hardiness zone. Those frost dates are not the ONLY factors, but they are much better than Hardiness zone for figuring planting dates.
http://garden.org/apps/calenda...
