Planting Cannas is a little like growing a bit of the tropics in your garden. If you live in USDA growing zones 8-10 than Cannas can be treated as perennials but for the rest of us, they must be treated as an annual flower. Cannas are very sensitive to cold temperatures; a frost will kill the foliage above the ground and a cold snap where the ground freezes will kill the plant entirely. For these reasons Cannas should be planted after all potential damage from frost or freezing is past. In many places, this is around Mother’s Day but in the Upper Midwest and Northeast, this date could be as late as Memorial Day. In those areas, you can start Cannas indoors to get a jump on the growing season.
When planting Cannas it is important that the soil be consistently moist. Using a mulch is a good way to help the soil retain this necessary moisture and they should be planted at a depth of 5 to 6 inches. Cannas thrive in locations that receive full sun for most of the day but they will tolerate some afternoon shade. Although Cannas can grow 5 to 6 feet tall they never need staking or other supports. The last several years have seen the introduction of new varieties of Canna that only grow 2 to 3 feet tall and this trait makes these Cannas ideal for pots and containers.
Cannas bloom 8 to 12 weeks after they are planted which means in most places they bloom later in the summer through the fall. New colors are being bred each year and they come in variations of yellow, red, pink and orange. Fortunately, while we patiently await these beautiful flowers their attractive banana-like foliage, which comes in hues such as green or maroon, adds unique visual interest to your garden. Newer varieties even have variegated leaves too!
During the growing season Cannas really do need a minimal amount of care. They rarely have problems with pests or diseases and as long as the spent flowers are removed they will bloom until cold weather arrives. This process, known as deadheading, channels the plant's energy into producing more flowers. The fact that Cannas love the heat often means they start to arrive when other flowers have already finished blooming. This gives your garden a boost of color just at the right time. If all of these benefits don’t make them worth growing Cannas have one additional characteristic that makes them an attractive addition to your yard. Although they’re blooming cycle puts them in the category of an annual, it is possible to harvest the Canna tubers and store them over the winter to plant them again next year!
After the first frost kills the foliage remove it leaving about 4 to 6 inches of stem above the soil line. Dig up the tuber, rinse the soil off and then allow them it to dry out for a day or two. You can then put several tubers in a plastic grocery bag and add either peat moss or a moist paper towel to the bag. Store the bag in a place that maintains temperatures between 40 to 60 degrees to avoid freezing or the formation of mold. Simply check the bag monthly to see if a little more water is needed and you are ready to plant them again in the spring. Although their tropical appearance makes Cannas seem like they are difficult to grow the truth is they are suitable for any gardener, including you!