By Cynthia W. Mueller
Master Gardener, Galveston County
Consider including some cannas in your gardening plans for next spring. There is no easier way to create a lush, tropical look quickly and inexpensively. Choose from old favorites as well as newer varieties with brightly colored foliage, and decide on the colors and sizes that will best add permanent color accents to your landscape. Cannas fit well into the current concept of water-wise gardening. They are easily grown and do not require large amounts of water in order to thrive.
The range of colors, flower styles, and the long blooming period of modern cannas have greatly improved these old garden favorites from Victorian times. Forget those memories of seedy common cannas like Grandma grew, with thick masses of stalks up to 6 or 8 feet tall, topped with tiny heads of flowers, which often dried in place and did not fall cleanly from the plant. Modern breeders have concentrated on creating shorter plants with up to 5 bloom spikes on the same stalk - when one spike finishes, others will take its place. Varieties are now available that are striped red, brown, green, pink or yellow in unique combinations - who has to have flowers, with foliage this distinctive?
At last, gardeners with questions about identity and sources for cannas have available to them an excellent book with a large range of color photographs: The Gardenerís Guide to Growing Cannas, by Ian Cooke (Timber Press, Portand, Ore., 2001, $29.95). Topics include cultivation, pests and diseases, propagation, descriptions of the different species and hybrids, histories of the old breeders and the strains they created, where to buy cannas, websites of interest, problem names, and much more. The gallery of variety photos alone will be worth the cost of the book.
Cannas may be planted in almost any good, well-worked garden soil, preferably conditioned with a heavy dressing of manure or compost. It is important to order planting stock while the rhizomes are fresh and plump, at the beginning of the season, rather than when they have become brown and shriveled by sitting out too long in packages at the garden center. It is better to start the tubers indoors in containers in a warmer atmosphere, rather than outside in the ground before the danger of freezing or becoming water-logged is past. In areas where the ground might freeze, itís necessary to take up the rhizomes and store them for the winter. Keep them in a container of potting medium in a protected place, and give just enough moisture to keep them plump. Full sun is best: Ian Cooke points out that there will be less flowering in more shaded parts of the garden, and the bright colors of the foliage varieties will not be as strong. After the plants have begun to grow, a covering of mulch will help to hold down weeds and conserve moisture. Fertilize in mid-season with a good general fertilizer.
Make a legible label for each variety. Some gardeners will bury the label inside a small jar under the initial plants so that there will be no mistakes about identity. After the first spike has finished blooming, wait to see if another spike on the same stalk will emerge. After flowering is finished, cut off the entire stalk at the base (that particular stem will not bloom again). This will help to thin out and Ďopen upí the clump. In the fall, when foliage becomes ratty or has been burned by frost, wait until the stalks are brown and dry before trimming them off several inches above the ground.
Insects such as the canna leaf roller (Calpodes ethlius), which will turn into the small golden-brown Brazilian Skipper butterfly, may be controlled on the leaves by applying a solution of Bt (Bacillus thuringiensis), insecticidal soap, or other chemical control once a week. Apply the insecticide around and into the young leaves while they are still rolled up. Check older leaves for the tell-tale silken threads leaf-rollers spin to keep the leaves closed. Unroll leaves carefully if necessary and remove the caterpillars.