Hi David, Very interesting data, which pretty much proves what most have suspected. It would be interesting to see what soil temperatures are like at various depths in areas with much colder winters. I wonder just how cold my Crinum bulbispermum bulbs experience when it is -1F outside as it was a couple of times this winter, and solidly frozen all February though with snow cover most of the time. Also the Amaryllis belladonna bulbs by the wall in my school garden have survived many years, one is about to open now (dont see bloom spikes on others so far) and they still have some green foliage this year, being unable to grow at all this cold winter, they wait for spring and new foliar growth pushes up the burnt leaf tips from earlier unsuccessful growth. I am sure the building wall prevents deep freezing as I can zone push many plants there such as the amaryllis, Fuschia magellenica, Melianthus villosa, Pelargonium luridum, a dierama (though some are hardy in open ground), zephyran thus candida and what I think is desert sunset strain, and a diospyros lyciodes (note all the shrubs die back to ground except in the mildest of winters). Crocosmia aurea which also surivives in the open, does even better against the wall, blooming earlier and more of the corms survive I think because in open ground probably the deepest ones are the ones that make it. Ernie DeMarie NY z7ish, where my gladioli hybrids, galtonia viridiflora, crinum moorei (in pots) crocosmia aurea, tritonia drakensbergensis (or whatever the taller of the two is called), and a Crinum bulbispermum are all in bloom right now among others.