Plan to repot your canna in the fall. Take care not to damage the rhizomes as you cut the pots away.  Trim the growth so about one inch extends from where the stem meets the rhizomes.  To divide, cut the rhizomes along the joint where the old meet the new making sure each piece has one or more eyes.  Store in damp, not soggy, peat moss for the winter and plant in the spring. If you are planting them back into containers, use pots that are at least 18 inches in diameter so the canna will have enough room to grow a strong root system.  Plant divided rhizomes in soil 4" to 6" deep.

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