Question
I live in the Poitou Charente region of France. I am certain that the town display Cannas are not dug up for winter. Should we cut them back and cover their tops with fleece or straw,or something else, or just cross our fingers and hope for the best. We have Calcire soil which has been well dug but tends to absorb the water.Thanks

Answer
Hi Sally,
Thanx for your question.  This is the place where the Battle of Poitiers and Charles Martel stopped the Moorish invasion of Western Europe, n'est-ce pas?  From what I have been able to determine.  You average temperatures very seldom fall below O degrees C.  Cannas are hardy to USDA Zone 7 which does experience freezing although the ground seldom freezes very deeply and that is the key to overwintering canna rhizomes.  As long as the soil does not freeze around the rhizomes, they will go dormant and rest until spring.  I would allow a frost to kill back the foliage.  It will wilt and turn black.  Just hack it off near the ground with a machete or sharp knife.  Cover this with a nice pile of dry straw, about 20 cm thick.  As long as the soil drains and does not sit and get soggy the rhizomes will be fine and they will continue to increase.  You can feed them with bone meal following the instructions on the package.  I think you meant calcic or calcite soil which means there is probably enough calcium in the soil.  You may want to amend the soil next year with some composted horse or cow manure.  Otherwise, soggy, cool soil, will result in rotted rhizomes.  I hope this helps.
Tom