Rick, Lots of good interesting information in your post. So much, I don't know where to start. But for the sake of discussion I just want to elaborate on a couple things. First the USDA zone hardiness chart. For readers that may not know, the hardiness zones are based on the average of the lowest temperature each year for a period of years for a given location. Since Anchorage has a maritime influence and somewhat of a micro climate it lowest wintertime temperatures are modified putting it within the same zone range as places like Chicago and Milwaukee. But during the three coldest months of Dec. Jan and Feb, even within the same zone of 5 and 5b, the temperature differences are significant, well maybe not to some, but in terms of climate data, they are substantial. And, one lowest temperature per month doesn't tell us what the other 29 or 30 days were nor how many total hours of real cold temperatures are experienced. To know that we'd have to integrate the entire area under the curve for each city. But to make a point, places like Chicago, Milwaukee, or Des Moines could have just one cold day a month and end up in zone 5 for that year while it's average temperature is/was warmer overall (as compared to Anchorage ). So, there must be a reason gardeners in Des Moines and Chicago can grow beautiful OT's, etc., and then leave the bulbs in the ground year after year, while those in Anchorage can not. And I think it's all about duration of persistent cold and how far down that cold drives the frost level and what the soil temperature at bulb level is and for what duration. What do you think?
Another point about soil temperature, Rick. Once you start taking soil temperatures, you would be in for a real surprise; it's much warmer than you would ever expect, even without a mulch. This good ol' earth contains a lot of heat and that continually and constantly is rising toward the surface. and the farther south you go the warmer the soil is to begin with. I'll bet you a good lunch that your soil temperature at bulb level right now in your zone 4 is still at least 5'F warmer than in zone 5 in Anchorage.
Asiatics? Yeah, their tough. Funny, how we learn by accidental experience sometimes. I once had quite a few extra of Ed McRae's Pixies so I threw them in a Lily Garden shipping box and closed it without covering the bulbs even. I had intended to take them up to the farm the next mornimg, but I forgot 'em. Anyway, while I was gone for a week, my wife put them under a chair on my ponderosa type porch. Out of sight with winter fast approaching, I really forgot about them then---until the next April when I discovered them. We had experienced several days of below zero weather that winter, like 10 below. They were dehydrated and soft, but I did finally take them to the farm and planted them that following Spring. They all lived, albeit a little spindly with only some flowers. But lose Asiatic bulblets left on the surface here all winter will survive just fine if the voles don't find them. Orientals, OT's, Trumpets, would never survive that. So burying pots of those in Anchorage with lots of mulch might work, or maybe not because of the duration thing. I dono. But like we say--there's one way to find out--try it.
Anchorage, D 25/13, J 23,/11, F 27/14.
Chicago: D 36/23, J 32/18, F 34/20.
Milw., D 33/20, J 29/16, F 33/19.
