Somewhat tubular and lily-like, canna flowers come in shades and combinations of yellow, orange, red, and pink and are borne on tall stalks poking out of the foliage. Rhizomes planted in spring after the last frost will take a few weeks to sprout but will then grow at a rapid pace and often flower in the first year. Because most cannas sold today are the result of many crosses, cannas are rarely classified and are simply considered hybrids. To keep your plants flowering throughout the season, deadhead them as the blooms start to fade. If you prefer to grow cannas for their foliage alone, you can cut back the flower stalks before they even have a chance to bloom. The size and amount of blooms of cannas are linked to the number of “eyes” on a rhizome. The more eyes, the bigger plant, and better its blooms. Look for rhizomes with three to five eyes, and plant them in spring with the eyes facing up four to five inches deep. Or, if you’d like to get a head start on the season, pot them up indoors, four to six weeks before your average last frost date, and move them out once the temperature warms. Keep the rhizomes moist but not soaking wet.
Light
Cannas do best in full sun. This means they may need more water in really hot climates, but they need heat to spur their growth. In the hottest areas, some afternoon shade helps flowers last longer.
Soil
Plant cannas in rich, moist soil, ideally with a slightly acidic to neutral soil pH.
Water
Cannas need consistent water and evenly moist soil. Water often, especially in extreme heat. Insufficient water will cause the leaves to tear or crack.
Temperature and Humidity
Blooming depends on the climate and weather. In areas with cool springs, the plants may be slow to get started. Potting them up indoors, before your average last frost date, and moving them out while they are already growing, will help them bloom earlier. As tropical plants, cannas prefer humid air but can tolerate relative dryness, especially if they are properly watered.
Fertilizer
In addition to needing lots of water, cannas are hungry plants, although they store some food in their rhizomes. Feed them in early spring and midsummer, using a balanced fertilizer. For the amount, follow the product label instructions.
Types of Canna Lilies
‘Lucifer’: red flowers with yellow borders; green leaves; two feet tall’The President’: scarlet blossoms; green leaves; three to three and one-half feet tall’Pretoria’ (‘Bengal Tiger’): orange flowers; yellow and green striped foliage; four to six feet tall’Stuttgart’: orange flowers; green and white variegated foliage; three to four feet tall’Tropicanna’: dark variegated leaves with large, orange flowers; also offered with black leaves and gold flowers; four to six feet tall
Propagating Canna Lily
Since most of the newer varieties are hybrids, canna lilies are generally grown from rhizomes rather than seeds. If you live in a climate with frost and would like to preserve cannas for the next season, cut the foliage and stem to six inches. Then, dig up the rhizomes and let them dry in a protected, shady spot. When dry, shake off the excess soil, wrap the rhizomes in newspaper, and store them in a dark, cool location until spring. Check on them periodically to make sure they are not rotting or drying out. Over a growing season, a single canna rhizome can become much larger, developing offshoot structures. Well-developed offshoots can be cut away from the main rhizome to become new plants. Look for shoots that have at least two to three growing points or eyes. This can be done in the spring, after you bring the rhizomes out of storage, or when you dig them up for storage in the fall.
Potting and Repotting Canna Lily
Canna lily grown in a pot will need rich potting soil and good drainage. Adding pebbles at the bottom of a pot with good drainage holes is recommended. The pot itself should be rather large, at least 12 inches in diameter, and made of any medium as long as the aforementioned drainage holes are abundant. It should also be very sturdy, as these plants can grow rather tall. The rhizomes should be planted four to five inches deep.
Overwintering
In warmer zones, canna lilies often survive winter in the ground. If the temperatures dip below freezing for several months, it’s best to bring canna lilies inside to overwinter. Do this by gently lifting the clump of rhizomes and placing the plant in a pot. Cover the pot and tuck it away in a cool, dry place, such as an unheated garage. Set the lilies back into the ground as soon as the soil is soft enough to work.
Common Pests and Plant Diseases
Canna leaves are covered with a waxy substance that repels water and protects against fungus. They may be bothered by rust or bacterial blight, especially in poorly drained soils. Pest problems can include leaf rollers and caterpillars while slugs and snails may munch on the leaves.
How to Get Canna Lily to Bloom
To keep canna lily blooming all season, make sure the plant has full sun, as well as a spring feeding of 5-10-5 fertilizer. For the amount, follow the product label instructions. Give them plenty of water weekly and deadhead the blooms as they begin to fade, thus encouraging more growth. Check to be sure the rhizomes are no more than two to three inches deep in the soil, as planting them too deep will stunt the plant’s growth. Canna lilies that are too crowded will fight for nutrients, and that means fewer blooms. To remedy this situation, divide the lilies every two to three years.
Common Problems With Canna Lily
Though canna lily often grows beautifully for years, the plant might encounter some problems. Here are the most common.
Leaves Stuck Together or Covered in Black Droppings
This is the work of the leaf roller, a tiny pest that can pull together leaves with silky strands to hide and feed. A good insecticide will do the trick.
Holes in Leaves
When you see holes in leaves, that’s the telltale sign of snails or slugs. Remove these by hand or use a horticultural oil to keep them away.
Curling Leaves
Aphids leave a sticky sap behind that can curl up the leaves of your plant, leaving it quite unsightly. Blast them away with a water hose or use insecticide for serious infestations.
Fuzzy Mold
A plant covered in fuzzy mold is infected with Botrytis blight. This fungus can be treated with a fungicide. If the infection is severe, consider removing the plant.
