Don't be fooled when it comes to planting canna lilies. Although cannas grow from bulbs or rhizomes, they are hardly diminutive little flowers like crocuses or daffodils. Depending on the variety, cannas grow up from 3 to 6 feet tall and wide. Use them at the back of a flower garden, as alternatives to shrubs or as foundation plantings. In addition, the planting method of canna bulbs differs greatly than those for planting daffodils or tulips
Unlike many bulbs, cannas should be planted in the spring, not autumn. Wait until all danger of a killing frost passes. Depending on your planting region, the date ranges from March to May.
Cannas tolerate moist soil better than many bulbs, but don't plant them in boggy areas. They need at least four hours of sunlight. Their foliage and flowers both tend toward the large and tropical, so don't place them near delicate flowers whose ethereal charm might be overshadowed by canna's showy color and size.
Digging Holes and Bulb Placement
Dig holes about 4 inches deep and 12 to 18 inches apart, depending on variety. Place the canna rhizomes in the holes, cover with several inches of soil, and water thoroughly. If desired, add a handful of high nitrogen fertilizer, or commercial tomato or rose fertilizer to the planting hole.
Which Side Up?
Looking a bit like a ginger root, canna rhizomes are long and narrow and usually feature visible growth nodules, called eyes. Place these eyes facing up. Plant the cannas horizontally rather than vertically.
Don't grow cannas in zones 5 or 6 or lower if you won't have the time or patience to dig them up in the fall. When that time comes, wait a few days after frost, cut them back to 3 to 4 inches of stem, dig the bulbs up and allow them to dry for several hours before storing them. They will store best if you apply a fungicide and dry them on shelves or racks in a cool, dry place, according to Purdue University.
Planting Older Bulbs
After cannas reach two or three years of age, the clumps get large enough that they can be divided. Include a bit of the growth nodule, also known as an eye, in each replanted clump. Southern gardeners must dig up cannas in early spring for this procedure, while northern gardeners may divide the stored bulbs before planting them.
Garden writer Barbara Damrosh suggests planting bulbs in wire cages to deter gophers and other digging pests. Make a simple cage from chicken wire, place the canna in the cage, and cover with soil. The stems will grow through the cage, but digging pests can't remove the actual rhizome.
Choose large tubs or planters with drainage holes at the bottom. Fill the containers with good-quality potting soil. Place the bulbs 4 to 6 inches deep and 12 to 18 inches apart in the tubs. Soak the soil thoroughly after planting. In northern gardens, either store the entire pot in cool, dry place or dig the canna bulbs up and store them for the winter. Don't attempt to grow the flowers indoors in the winter, because the plants need several months rest between bloom times.