I have a total crush on canna lilies also called cannas. They are spectacular and very easy to grow. However, canna lilies are not for the faint of heart. They are generally huge with large showy flowers, and when you grow them, you are making a visual statement with an exclamation mark.
I love canna flowers, but I grow them for the leaves. Canna leaves are the show stoppers--wide and long they can be a wild stripy pattern, and their colors can range from yellows to oranges to almost black and neon pink. Watching canna leaves shoot up and then unfurl over a few days is miraculous and one of those gardening experiences that is both moving and poetic.
Cannas can be grown outside year round, if you live in a climate that is zone 7 or warmer. In cool climates the plants can be grown inside as houseplants or the rhizomes can be dug up, the soil shaken off and stored in a damp medium, in a cool, frost-free area for the winter.
My favorite varieties of cannas are 'Tropicana', 'Tropicana Black' and 'Tropicana Gold.' Each is spectacular and will grow from 4-6 feet tall. They are good humored plants, not demanding too much care. They are easy to plant and even if you are in a cold climate, you can grow the plants inside over the winter or cut off the rhizomes and keep them in a cool dry place.
Choosing Your Pot - For cannas, bigger is better. These are large plants so for aesthetic reasons and to increase your chances for large healthy plants, choose a pot that is at least 15-18 inches in diameter. Make sure your pot has good drainage, and fill it with a good quality potting soil.
Planting Cannas - While it is possible to buy plants that are already growing, it is common to grow cannas from the rhizomes, which are the underground roots. If you have Canna rhizomes, and live in a cold climate (less than zone 7), you can start them inside and move them out, once the night temperatures are consistently over 50 °F. To plant the rhizomes, place them 4 inches below the surface of the potting soil, making sure there are no air pockets and that they are surrounded by soil. Cannas are heavy feeders, so mix some slow release fertilizer into your potting soil before you plant them.
Caring for Cannas While cannas prefer full sun (6-8 hours of direct sunlight) they will survive in part sun (4-6 hours of direct sun). The prefer to be kept on the moist side and don't like to dry out completely. Cannas need to be fertilized regularly, with either a slow-release fertilizer, or a diluted liquid fertilizer.For more info on cannas:
Royal Horticultural Society Article