For the last three years I have been digging them up and putting them in brown
paper bags, storing them in a frost free closet in the garage. In spring I
replant them in pots. In a few weeks green shoots appear on the braches and
then grow rapidly. I avoid cutting off last year's leaves as long as possible.
This was a tip from Park Seed Co. here in the U.S.A.

Nancy Beckmann