I've got some cannas in pots & would like to transplant them into the garden. Is now (September) a good time to do it, or should I wait until Spring?
I am no expert so take this advice for what it is worth.
Canna should be hardy in your zone. Transplantation does place stress on the plant.
If you experience heavy frost and/or frozen soil keep the rhizomes in the pots under cover/indoors until danger of frost is past.