Carolyn - you're too warm of a zone for me to give good advice to, but I plant bareroots here when the ground's manageable. So I won't be burying bodies for another 2 months (I have to find the ground first). If you're worried about a late frost you can always cover with a temporary tent of newspaper & straw. There are a lot of wonderful nurseries there in TN... personally I'd ask them. It also depends on your soil - if it's super rocky I'd wait a little 'cuz of the thaw/freeze could screw up the root systems or make the canes into mush. Clay/sand doesn't have that much of a problem (not as much ground flexing).
