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EXOTIC PLANTS FOR THE HOME GARDEN

written by Marianne C. Ophardt WSU Extension Faculty for the Tri-City Herald, Kennewick, WA One of the newest trends in gardening is to create the atmosphere of a lush tropical paradise in the garden. This might seem an impossible task for local gardeners living in a desert area with cold winters,. However, there are some plants that we can grow to give our gardens a tropical flair. Large leaves, big bold flowers, and colorful foliage are some of the elements that can be used to create a garden design with a tropical feel. Lets take a look at several plants that can add that exotic touch. Canna: There are numerous varieties of cannas available for home gardens. Some of the older standard types can grow as tall as ten feet, but the newer dwarf varieties grow to a more modest two to three feet. These large-leaved plants have bold flowers in colors that include vibrant red, dark red, orange, coral, and salmon. The leaves may be plain green, but newer varieties certainly add ‘island heat’ to the garden with red, bronze, brown, black, or purple leaves. Some of the most exciting varieties have brightly variegated or striped foliage. To me cannas look like a bigger, bolder tropical version of the garden gladiolus. Their form is upright and not bushy, providing a striking vertical element to a garden design. If you’ve ever driven through the town of Quincy during the summer or early fall you’ll have noticed the bright, beautiful cannas lining the road as you enter town. They make an eye-catching welcome. Cannas grow from rhizomes and are native to the tropical regions of North America, South America, and Asia. The rhizomes are not considered hardy in our region and are typically dug and stored over the winter. They grow best in full sun with consistently moist soil. Cannas are a warm season plant and should only be planted after the soil has warmed up in the spring and all danger of frost is past. Plant the rhizomes horizontally about 5 inches deep and 12 to 18 inches apart, depending on the variety. Water them well to settle the soil and then keep the soil evenly moist. Fertilize them about once a month. Cannas can also be grown in containers. The dwarf varieties are most suitable for container growing… unless you have a very large container. In the fall, cannas must be dug up and stored over the winter where the rhizomes won’t be subjected to freezing temperatures. Once the frost kills the leaves, the rhizomes should be carefully dug and stored away. In the same manner as tuberous begonias, dahlias, and gladiola, trim the stem back and then pack the rhizomes in dry sphagnum moss or dry sawdust. Store them in a location where they’ll be cool (40 degrees) and dry. To replant them the next spring, first divide each rhizome into several portions, making sure each piece has several strong ‘eyes’ or buds. The entire rhizome without division can also be used to create a large clump of cannas. Hibiscus: If you’ve ever been to Hawaii or another tropical paradise, you have no doubt seen large tropical hibiscus blooms. Perhaps you have longed to be able to grow these exotics in your own garden. They’re not exactly the same, but hardy forms of hibiscus can be grown in northern climates like ours. Shrub hibiscus, commonly known as Rose-of-Sharon, (also sometimes called shrub Althea) is hardy in our region. It provides local gardeners a way to grow exotic looking plants right here in the desert. The Rose-of-Sharon (Hibiscus syriacus), a native of China and India, is considered a shrub or small tree, depending on how it’s pruned. Some can grow to a height of 12 feet, but 5 to 7 feet is an average height. Without it’s flowers, Rose-of-Sharon doesn’t have much to offer, but when in bloom it’s spectacular. Its large showy flowers come in a range of white, red, pink, purple, and even blue. Flowers types can be single or double and some single varieties have different color throats. The blooms can be quite large in size with some varieties even reaching a diameter of 12 inches. The Rose-of-Sharon is a ‘late bloomer,’ flowering later in the summer long after other flowering shrubs have ceased blooming. On older varieties, a green to brown somewhat unattractive seed capsule develops after the flowers fade. This capsule hangs on all fall and winter, detracting from the shrub’s appearance. Seeds dropped from these capsules often self sow and can create a weedy situation. However, newer cultivars have been bred to be fruitless. The Rose-of-Sharon is an older shrub that has been in cultivation for thousands of years. They thrive in heat and don’t need a lot of care. Like so many plants, they do best in full sun with a well-drained, moist soil, but they’re adaptable to different soil conditions. They’re also drought tolerant and don’t need copious amounts of water. They can be situated in partial shade, but will produce fewer flowers without full sun. The National Arboretum worked on breeding Rose-of-Sharon quite a while back and released a group of named cultivars (varieties) in the 60

s and 70

s. They’re sterile triploids, which means that they don’t set the ugly seed pods and they produce larger, earlier flowers. These cultivars include

Aphrodite

with pink-mauve single flowers and a dark magenta eye;

Diana

with white single flowers that remain open at night;

Minerva

with lavender-mauve single flowers; and ‘Helene’ with white flowers and maroon throats. Left alone and never pruned, Rose-of-Sharon has an upright vase-shaped growth habit that can become arching with age. To enhance bloom, prune the shrubs in late winter or early spring before new growth starts. This is important because the flowers are produced on the new year’s growth. If you prune during the spring or summer, you’ll be pruning off flowers. Heavy pruning will reduce the amount of flowers, but blooms will be bigger. Coleus: In the past coleus was a shade-loving annual plant, prized for its colorful foliage. In full sun the colors tended to fade or bleach out. However, the new ‘sun coleus’ varieties can be grown in full sun and are another exotic looking plant that can provide tropical flair to the garden. Some of the new cultivars also have larger leaves and even bolder, brighter colored leaves. While they do tolerate more sun, these annuals aren’t drought tolerant. Keep them evenly moist.

Published: 5/7/2005 1:42 PM

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