A lush tropical look, but tough enough to take it: That’s a tricky order for any gardener in this area. But it is possible. The proof is in the Thai-style garden at the Olbrich Botanical Gardens in Madison, Wis.
Across Starkweather Creek from the main gardens, a landscape intended to evoke southeastern Asia, with large leaves, twining vines and bold color, surrounds a traditional sala, a handcrafted ornamental pavilion imported from Thailand. The challenge, director of horticulture Jeff Epping says, is to maintain that tropical-looking garden in a Zone 4b-to-5a climate, “just a little bit tougher than the Chicago area.” Chicago is in Zone 5.
Part of the atmosphere comes from annuals — cannas, castor beans, elephant ears, sweet potato vine and coleus, all well-known as container or bedding plants. Part of it comes from banana plants, which overwinter indoors.
But Epping’s secret weapon is trees, shrubs and perennials — including some natives — that have a tropical air to their foliage or flowers but have proved, in the two years since the sala was built and the garden planted, that they can breeze through Madison’s winters. In the right setting, “even Virginia creeper has a very tropical feel to it,” Epping says.
Here are a few plants that will grow in Chicago as well as Wisconsin that Epping suggests to help set a scene from a hotter clime:
Umbrella magnolia (Magnolia tripetala): This tree, often with several trunks, has umbrellalike clusters of dark green leaves up to 10 inches long. “You don’t see it a lot in the landscape, but it fits well in the tropical theme,” Epping says. In the spring, it has large creamy bowl-shaped flowers (Warning: Some find the odor unpleasant.). A conelike fruit is rosy pink when it matures in late summer. Native to the eastern and southern United States, umbrella magnolia is hardy in Zones 5 to 9. In its original habitat — milder winters and somewhat acid soil — it may reach 30 feet. Umbrella magnolias grow well in partial shade, Epping says: “They can grow under a honey locust, but not under a Norway maple.”
Siberian greybeard (Spodiopogon sibiricus): “We tried bamboo without success,” Epping says, so he turned to this hardy Asian grass. It grows 3 to 4 feet high with flat tapered leaves that start out bright green and mellow to a red tint in fall. In summer, footlong panicles of bloom stand up above the foliage. Spodiopogon prefers light shade and is hardy to Zone 5.
Tiger Eyes cutleaf staghorn sumac (Rhus typhina `Bailtiger’): Staghorn sumac “is a native plant that you see everywhere,” Epping says. But this cultivar has spectacular foliage that starts out chartreuse and soon turns golden yellow. The long stems with feathery leaves make it look almost like a large fern. In fall, the plant turns gold, orange and scarlet, says the breeder, Bailey Nurseries in St. Paul. It is relatively compact, reaching about 6 feet wide, and prefers full sun. “It’s a great plant. But you have to control it if you have a small space,” he says. “Put it between sidewalks. It’s a spreader for sure.” Tiger Eyes sumac is hardy in Zones 4 to 8.
Clematis `Bill MacKenzie’: This British cultivar of the popular vine has bell-shaped yellow blooms, Epping says. In midsummer through autumn, each 2-inch bell-shaped yellow bloom has a dark red center. A twiner that can climb a trellis or a shrub, `Bill MacKenzie’ prefers sun or partial shade and is hardy in Zones 4 to 9.
Yellow trumpet vine (Campsis radicans `Flava’): A cultivar of a plant native to the Southeastern states, this version has 3-inch-long yellow trumpet-shaped flowers and small dark green leaves. It uses aerial roots to cling and climb up fences or walls, and is such a vigorous grower that it may be too robust and needs hard pruning in winter. Because it covers its support so quickly, trumpet vine often is used for a privacy screen, Epping says. The native species has orange to red blooms.
Swamp rose mallow (Hibiscus moschuetos): This large perennial, native to the U.S., looks “totally exotic,” Epping says, because of its large white or pink blooms, like ruffled trumpets. Leaves are lance-shaped and 3 to 9 inches long. Rose mallow requires a consistently moist location, such as near the Olbrich sala, which is almost surrounded by the creek, reflecting pools and a pebble pool. Yet “they are very hardy plants and easy to grow,” he says. Plant swamp rose mallow at a pond’s edge or in a pot in the pond water. Sometimes growing 6 feet tall, it needs full or partial sun and is hardy in Zones 5 to 9.
The Olbrich Botanical Gardens is open from 8 a.m. to 8 p.m. daily at 3330 Atwood Ave., Madison, Wis. Admission to the outdoor gardens is free; a butterfly exhibit runs through Aug. 15, with admission charges of $5 for adults and $3 for children. Call: 608-246-4550.
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In search of the `tropics’
Here are some mail-order sources for plants with a tropical look:
– Forestfarm Plant Nursery, call 541-846-7269 or see www.forestfarm.com. Carries umbrella magnolia (Magnolia tripetala). A print catalog is $5.
– Digging Dog Nursery, 707-937-1130 or see www.diggingdog.com. Carries Siberian greybeard (Spodiopogon sibiricus) and yellow trumpet vine (Campsis radicans `Flava’). Free printed catalog.
– Song Sparrow Perennial Farm, 800-553-3715 or see www.songsparrow.com. Carries Tiger Eyes cutleaf staghorn sumac (Rhus typhina `Bailtiger’) and Clematis `Bill MacKenzie’ on Web site but not in printed free catalog.
– Tripplebrook Farm, 413-527-4626 or see www.tripplebrookfarm.com. Carries swamp rose mallow (Hibiscus moschuetos) on Web site but not in free printed catalog.
— Beth Botts
