KOI POND vs. WATER GARDEN

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Water-loving cannas bring their own distinctive blends of bright and exuberant colors to the pond

By Sue Speichert
Original publication date:
Fall/Winter 1998


Once considered stodgy plants that only grandma would grow, cannas have made a colorful comeback in the perennial border. Now water-loving and water-tolerant cannas are making a bold statement in the water garden landscape, too. Blooming far longer than their terrestrial cousins, water cannas light up the pond from early summer through fall.

Cannas that are suitable for the water garden may be very generally separated into two broad categories. True water cannas, including those called the Longwood hybrids, grow well in saturated soil with water over their crowns. Water-tolerant cannas, on the other hand, have adapted to wet conditions but grow well in average soil as well. Unfortunately, there is no easy way to determine whether a land-based canna will grow in the pond. Trial and error appears to be the only method to find out if a particular cultivar is suitable for the water garden. For the sake of simplicity, we'll group both types of cannas under the general heading of "water cannas."

True Water Cannas
Cannas that are truly adapted to water include Canna flaccida, Canna glauca, and their hybrids. The first, C. flaccida, is native to Florida and is commonly known as Florida Water Canna. This species canna has clear yellow flowers with a shape reminiscent of daffodils. Blooms appear most heavily in the spring and then sporadically through the summer. Usually reaching a height of about 4 feet, Florida Water Canna has a narrow spread and attractive, medium green foliage. It grows readily with its crown submerged as far as 10 inches below the water surface.

Canna glauca is native to South America. Its native range now covers most of the southeastern United States, and it is not uncommon to see it growing along waterways in Georgia, Alabama, Florida, and Louisiana. It also has yellow flowers and can grow up to 6 feet or more. It, too, enjoys several inches of water over the crown.

The famed Longwood Cannas are the direct offspring of Canna glauca. In the early 1970's, Dr. Robert Armstrong crossed Canna glauca with terrestrial canna hybrids. These offspring are identifiable because of their blue-green foliage, for which Canna glauca itself was named. Although one of their parents grew only on land, Longwood hybrids are just as water-tolerant as Canna glauca. All of the Longwood Cannas will grow easily in water that is several inches deep.

Longwood hybrid cannas usually grow anywhere from 2 to 6 feet tall in our northern Indiana garden, depending on cultivar, and have a narrow spread of 2 or 3 feet. Their flowers are commonly referred to as ‘plumeria type' because the petals are thinner and more recurved.

‘Ra' is the tallest of the Longwood hybrids, reaching to about 6 feet with bright yellow flowers the color of buttered sunshine. ‘Endeavor' is slightly shorter, approximately 5 to 6 feet or so, and is distinguished by its butterfly-like flowers that are a saucy, bright red. Slightly smaller is ‘Taney,' which has intense orange blooms. The smallest of the Longwood hybrids is ‘Erebus,' which grows to about 3 feet and has soft, delicate, peach blooms that approach the color of salmon.

Terrestrial Cannas That Tolerate Water
Cannas that are truly land-loving but have adapted to wet soil are becoming more readily available. Each of these selections grows best in either very moist soil at the edge of the pond. Some will tolerate just a slight amount of water over their crown.

One better-known favorite that has made the transition from land to pond-edge is ‘Florence Vaughn.' This cultivar reaches 4 to 5 feet and has giant flowers that look like orange gladiolus edged in yellow.

Two other terrestrial types that are suited to the water garden have been developed and hybridized by Herb Kelly, a well known canna breeder in Sanger, California. ‘Intrigue' has pink-orange plumeria-type flowers accented by dark purple foliage. A tall canna, it can reach from 6 to 10 feet in height. ‘Panache' has delicate, vanilla-cream plumeria-type blossoms that are marked by raspberry in the center. It grows shorter, to about 5 or 6 feet tall.

Some water-adapted cannas are as highly regarded for their flamboyant, variegated foliage as they are for their flower. ‘Pretoria' has boldly-striped leaves that resemble bananas. The foliage is bright green streaked in yellow. As if that weren't enough, the canna bursts forth with large, mandarin-orange gladiola-type flowers that float 5 to 8 feet above the ground. A closely related cultivar is ‘Striped Beauty' (also known as ‘Bengal Tiger') which has yellow and white gladiola-type flowers and foliage streaked in yellow and red. It, too, can reach almost 8 feet in height. Because the foliage of these cultivars is so intense, some gardeners find the blooms so gaudy that they cut the flower stems before the buds have a chance to open.

Recent introductions are even more stunning than ‘Striped Beauty' and ‘Pretoria.' Consider ‘Durban' and ‘Phasion.' Both have foliage heavily veined in gold and flushed in red, giving the leaves a coppery and almost electric appearance. ‘Durban' has tomato-red gladiola-type flowers, while those of ‘Phasion' are more orange. The two are easily and often confused, and in England, ‘Durban' and ‘Phasion' are sold as the same cultivar. Each grows anywhere from 5 to 8 feet tall and performs best at the very edge of the pond in soil that is constantly saturated. If you don't want red or orange flowers, then choose the soft hues of ‘Pink Sunburst.' It has yellow and green foliage that is flushed pink and accented by pink flowers. ‘Black Knight,' a terrestrial canna that adapts well to wet areas, has purple leaves with green stripes. As if this weren't enough, it has large blooms that are swirled in orange, yellow and red.

Planting and Seasonal Care and Maintenance
All water cannas are lovers of the tropics. They must be protected from frost and, in colder climates, may have to be brought indoors to spend the winter months. They also grow best in full sun, needing at least 4 or 5 hours of sunlight in order to grow and flower well.

It's best to grow water canna in a large, wide pot that is deep enough to act as a sturdy base to prevent the plant from falling over in the wind. The rhizome of the canna can be planted several inches below the soil surface, too, so that the plant has greater support from wind. Heavy clay soil is the best potting medium, since sand can shift and cause the plant to topple over unexpectedly.

Cannas are among the least fussy of water plants. In summer they benefit from monthly doses of fertilizer. They look best if spent leaves and flowers are removed. To prompt the canna to produce more blooms, cut off the top portion of the flower stalk once all the blossoms are spent.

In milder climates where a heavy freeze is unlikely, water cannas will easily survive the winter in the pond. In colder areas, the pots should be brought indoors when the winds grow cold. Gradually dry down the soil and cut off dead foliage. Remove the pot and break away the soil and you will find the rhizome that can remain dormant through the winter. Clean the rhizome so that it is free of soil and dead roots. Store it in a ventilated plastic container of damp sand or peat moss until the spring. When warm weather returns and the water temperature is consistently at approximately 65 degrees F, plant the rhizome deep in a large, wide pot and return the plant to the pond.

Cannas may also be overwintered indoors, by keeping them warm and giving them plenty of water and sunlight. Their growth will slow and may be somewhat leggy, but come spring their normal, healthy green color will return.

Diseases and Insects
Only a few pests affect water cannas. Aphids can sometimes appear, but they are easily removed with a stiff spray of water. In heavier infestations, use an insecticidal soap recommended for aphid control, but make sure to remove the canna from the pond before you begin treatment. Japanese Beetles sometimes eat the foliage of our water cannas in mid- to late summer, giving the leaves a lacy and "skeletonized" look. We take the beetles off by hand and throw them in the pond for the fish to eat, since Japanese Beetles can't swim. Our biggest problem with cannas has been winter attacks from spider mites or mealy bugs while the plants are overwintering indoors. Usually we control the insects by removing the contaminated stalks to the base of the plant and throwing the stalks away.

Canna rust is another affliction that is not uncommon. You can tell a canna has rust when you see orange spots on the leaves. Soon the plant will begin to wither and die. The disease is easily transmitted on dead and dying foliage, and good sanitation is key. When we find a canna infected with rust, we cut the stalks back to the crown of the plant (all the way to the soil line), throw all the foliage away, and scrape a bit of the top soil off the pot just in case any small parts of dead foliage fell into the soil.

Care-free and colorful, cannas are among the most valuable additions to the pond. They are excellent in container water gardens either alone or combined with low-growing aquatics such as Parrot Feather or Bacopa. Already popular in the perennial landscape, they are making a big splash in water features as well.

Latin Name Canna flaccida, Canna glauca, Canna x hybrids

Common Name Water Canna

Hardiness USDA Zones 7 (warmer with protection) to 11

Exposure Prefers full sun, grows in some shade

Cultivars
‘Black Knight,' orange, red and yellow flowers, purple leaves with green stripes, grows to 6 ft, water depth moist to 1"

‘Durban' bright red flowers with red/gold flushed foliage, grows 5 to 8 ft, water depth moist

‘Endeavor' (Longwood hybrid), red, grows to 5 ft, water depth moist to 6"

‘Erebus' (Longwood hybrid), peach, grows to 3 ft, water depth moist to 6"

‘Florence Vaughn,' orange and yellow, grows to 4 or 5 ft, water depth moist

‘Intrigue,' pink with purple foliage, grows 6 to 10 ft, water depth moist

‘Panache,' cream flowers with raspberry center, grows to 5 or 6 ft, water depth moist

‘Phasion' (tm ‘Tropicanna'), orange flowers with red/gold flushed foliage, grows 5 to 8 ft, water depth moist

‘Pink Sunburst,' soft pink flowers, foliage with yellow stripes flushed in pink, grows 4 ft, water depth moist to 1"

‘Pretoria,' orange flowers with striped foliage, grows 5 to 8 ft, water depth moist to 1"

‘Ra' (Longwood hybrid), yellow, grows to 6 ft, water depth moist to 6"

‘Striped Beauty' (aka ‘Bengal Tiger'), yellow and white flowers with striped foliage, grows to 8 ft, water depth moist to 1"

‘Stuttgart,' flowers open pale orange and mature to passion fruit orange, foliage heavily streaked in white, grows to 7 ft, water depth moist to 1"

‘Taney' (Longwood hybrid), orange, grows to 4 ft, water depth moist to 6"