The canna is called a lily but doesn’t belong to the same plant family. Boasting attractive leaves, these plants grow from rhizomes and produce flowers in a rainbow of colors that bloom in midsummer through fall in most climate zones. If you give them full sun to part shade, plenty of water and fertilizer, your cannas will do well. They make lovely container plants and do best when you plant them in soil that remains moist. When you collect and plant the seeds, the canna that grows might not be an exact replica of its parent because many varieties are hybrids.
Collect seeds after the flowers have finished blooming for the year. Rub off all plant material from the seeds and allow them to dry slightly in a warm, dark, dry, well-ventilated area for about one week.
Scarify the seeds one by one by rubbing them with sandpaper. Do not to sand away too much of the seed—stop sanding when you begin to see white through the hard, black coating.
Place the seeds in a bowl of hot water and allow them to soak for one to two days.
Fill nursery pots or flats with a rich, well-draining potting mix. Plant the scarified seeds about a half-inch deep.
Place your pots or flats in an area that receives full sun (at least six hours per day), and protect them from cold temperatures. Keep the soil moist. Seeds will germinate within two weeks.
Transplant the seedlings to small pots when they are 2 inches tall. The pots should be 4 to 6 inches in diameter.
Transplant young cannas to their outdoor location after the final spring frost. Leave 2 feet between plants and make sure the area drains well.