Hibiscus and Canna
As a pond builder or retailer, you’ve likely received requests from customers who want to create a lush, tropical atmosphere in their backyards. Maybe they dream of living on a tropical island surrounded by vibrant blooms, warm salty breezes, and tranquil pools of water. Though the tropics are more than a hop, skip and a jump away from the majority of us, it is still possible to create an oasis in your customers’ backyard. Two exceptional groups of plants that can be used to achieve this goal include species and hybrids of Hibiscus and Canna that are adapted to growing in bogs or shallow water.
Displaying large showy blooms, Swamp Hibiscus (Hibiscus moscheutos) is a popular hardy plant with a distinctly tropical appearance. Hardy to USDA Zone 4, this eye-catching species is native to wetlands, marshes, and swampy forests of the Southeastern United States. It can be gradually adapted to grow in water up to 6˝ over the crown of the plant. Today’s selections are the results of years of hybridization aimed at creating a number of appealing cultivars in a wide range of colors.
A group of compact H. moscheutos hybrids known as the Luna series was developed by Ball Horticultural Company. These are available in four colors – ‘Luna Blush,’ with 6-7˝ white flowers with light pink rims and deep red centers, ‘Luna White,’ which is pure white with a red center, ‘Luna Pink Swirl,’ which has light pink and cream blooms, and ‘Luna Red,’ which boasts 7-8˝ burgundy flowers. Reaching only 2-3´ tall, these plants have a compact growth habit not found in earlier cultivars. ‘Southern Belle Mix’ is another popular cultivar with large, maple-like green leaves and 10-12˝ blooms in an array of colors from white to pink to red. Other taller H. moscheutos hybrids include ‘Blue River II,’ which grows 4-5´ tall and graces the pondscape with 10˝ pure white flowers and dusky green leaves. ‘Fireball’ grows to 4´ tall and showcases dark purple-green maple-like foliage and is accented with deep burgundy blooms.
Hibiscus coccineus, known by the common name of Scarlet Rosemallow, is another valuable addition to the pond or garden. Blooming in late summer, the flowers of this southern native are a brilliant red, and while much smaller than those of the Swamp Hibiscus, are arranged in plentiful clusters on the tips of graceful stems creating a showy display of color and style. Hardy to zone 7, it can be grown in moist soil surrounding the pond or in water up to 3˝ over the crown of the plant. A white blooming hybrid, ‘Alba,’ is also available.
If you live in an area where these varieties are hardy, you can over-winter them by planting them in a garden bed and mulching them heavily. In the spring, the plants can be divided and repotted for use in the pond. When potting, use a heavy clay loam or an aquatic planting mix. Traditional garden mixes contain peat and perlite, materials that are very light and will float to the surface.
If you have ever been to Hawaii, you have probably seen Hawaiian Hibiscus (Hibiscus rosa-sinensis), the state flower. A native of Southeast Asia, it is one of the most popular ornamental shrubs used in tropical climates. In the wild, it can grow to 30´ tall, but in most areas of the United States it will only grow to a maximum of about 10´ tall. It can be grown outdoors in temperate climates during the summer months and brought indoors as a houseplant in the fall. With varieties available in every color except blue, this exotic plant will add beauty to any garden.
Far less common than the Hawaiian Hibiscus, Hibiscus acetosella ‘Maple Sugar’ is a tropical valued for its deep maroon foliage. The species is native to East and Central Africa and requires full sun to thrive. It should be pinched back and staked to control its rambling growth habit of up to 5 feet. Blooms do not appear until late autumn in most areas and are a deep maroon that blend well with the foliage. Hardy only to USDA Zone 10, this unique plant should be transferred indoors once temperatures drop below 55 degrees or simply treated as an annual.
Another eye-catching tropical, Abelmoschus (formerly Hibiscus) manihot, blooms in spring and summer with beautiful light-yellow flowers. This species is great for moist, boggy soils and grows 3-4´ tall. Hardy to zone 9, it should also be moved indoors to a greenhouse or home for the winter in colder areas. To encourage extended blooming, be sure to clip off any seed heads that form, as flowering will be diminished if these pods are allowed to mature.
Though tropical hibiscus should not be submerged in water, they work well as background plantings around your pond and can be placed in containers to ease the task of moving them indoors for the winter months. Plant in well-drained soil and fertilize regularly throughout the growing season to ensure optimum growth and blooming.
With bold, luxurious foliage available in an array of rich colors from dark green to deep purple to variegation of yellow or white and green, these stunning plants create a dramatic tropical atmosphere when planted in groups or as single specimens.
Canna ‘Pretoria’ (also sold as ‘Bengal Tiger’) is an especially eye-catching variety with banana-like foliage striped with bold yellow and green. Large orange iris-like flowers streaked in red appear in summer and last into the fall. An excellent specimen plant, it can grow 4-6´ tall and can be placed in water up to 6˝ over the pot. Canna ‘Stuttgart’ is another showy cultivar that can grow to 6´ tall and can be placed in water up to 10˝ over the crown of the plant. Its dark green leaves with white variegation are complemented by peachy-pink blooms in mid-summer. Placing this cultivar in areas that receive some shade in the afternoon will protect its foliage from being scorched by the hot sun.
Other notable varieties include Canna ‘Cleopatra’ which boasts dark green foliage with deep red stripes and brilliant gold blooms streaked with red, and Canna ‘Watermelon’ which showcases soft watermelon colored blooms accented by light blue-green foliage. Each of these varieties grows 4-5´ tall and prefers a location with full sun.
Another group of Canna hybrids was developed at Longwood Gardens in the early 1970’s. These hybrids were created by crossing Canna glauca, a species adapted to growing in standing water, with terrestrial cannas and resulted in four hybrids: ‘Endeavor’(scarlet red blooms), ‘Erebus’ (soft pink blooms), ‘Ra’ (bright yellow flowers), and ‘Taney,’ which boasts apricot colored blooms.
To over-winter cannas in areas where they are not hardy (they are generally hardy in USDA Zones 7 and warmer), cut the foliage back once it has been hit by the first frost and dig up the tubers. You can divide larger tubers at this time and store them in peat moss in a basement or garage for the winter months. Dusting the tubers with a fungicide prior to storing them can also be helpful. You can then pot the plants again in the spring once the danger of frost has passed.
Thalia dealbata, also known as Hardy Canna or Powdery Thalia, is not a true canna, but is worthy of mention as well. Native to the Southeastern United States, it is hardy from USDA Zones 5-11. One of my personal favorites, it has an impressive architectural leaf structure and bold blue-green leaves dusted with a powdery white coating. This graceful plant reaches a height of 6´. Small lavender flowers resembling clusters of tiny grapes appear in early summer and are held on 8˝ stems. This plant prefers an area with full sun and can grow in water up to 12˝ over the crown of the plant. To over-winter in areas where the species is hardy, simply sink the container to the deepest part of your pond. You can divide plants outgrowing their pots in the spring and repot them using a heavy topsoil.
While a few of the varieties discussed require extra care during the winter months in many areas, your customers will be rewarded with a lush backyard paradise filled with exotic blooms and luxurious foliage that can be enjoyed throughout the growing season. Now if we could only find a way to simulate those warm tropical breezes…
(Be sure to take a look at the pictures and charts.)
Note - all photos copyright Hughes Water Gardens unless otherwise stated
Company Sarah P. Duke Gardens
Bio Tamara Kilbane is the horticulturist in charge of aquatic plants at Denver Botanic Gardens in Denver, Colorado. A graduate of Oregon State University,...
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