"Andrew Ostrander" expounded:

Plant them now sounds like good advice, but there's nothing wrong with
letting them freeze. Here (zone 3) their entire root systems certainly
freeze every winter, but they come back. What is generally considered
harmful is for plants to undergo cycles of freezing and thawing, so put the
pots somewhere (sunk in the ground recommended) so they don't thaw and
refreeze.

Absolutely true. I left several out, exposed, on a cement slab over a
winter long ago, the following spring they were sprouting on the
cement. I planted them and they barely skipped a beat. I don't
advise treating plants this way, but it's really hard to kill a hosta.

--
Ann, Gardening in zone 6a
Just south of Boston, MA
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