Here in Northern California, zone 9, I've had minimal luck with storing p-stems in a garage. They seem to do much better outside covered in greenhouse plastic, where the frost won't get them and neither will the rains.
The "storing your corms in a root cellar" method seems more appropriate for climates where it gets freezing cold in the winter, yet you start getting some relatively warm days in Febuary and March (Florida, GA, MS, AL, etc are good examples).
Here's a Pisang Ceylon kept under greenhouse plastic-the pastic was blown off a few times from the make-shift shelter. The leaves stayed on, and I watered twice I think the whole time from late November thru early March. All plants remained potted. It's now in full sun and is doing well. When kept in the basement it sets the plants back by about a month, but with this method, they start growing right away as soon as it's warm enough:
I had a dwarf brazilian last year that was purchased around September and it had maybe 4-5 leaves by the time I had to place it in the basement. All the leaves were chopped off, and the corm eventually rotted.
Last year, I acquired a corm of Pisang raja with the same exact circumstance:it was started very late in the season and only had enough time to produce 3-4 leaves before the cold set it. This time, I kept it under greenhouse plastic in a makeshift shelter in full sun. Leaves were kept on. I had to water it maybe 8 or 9 times since this shelter was in full sun, but the plant didn't skip a heart beat, here it is now:
Lastly, here's dwarf Orinoco: it's pretty much bullet proof and would have probably survived the garage torture chamber, but it preferred the makeshift shelter:
