The words tropical vines conjure up many images--Tarzan swinging though the jungle, warm islands with lush vegetation, brilliant flowers attracting butterflies and birds--but always plants that are exotic, colorful, and king-size. However, if you don't live in Hawaii, parts of coastal California, or southern Florida (humid parts of USDA Climate Hardiness Zones 10 and 11), you've probably dismissed the possibility of growing tropical vines. But think again: provided you have a greenhouse or large south-facing window and are willing to give these plants a little extra care, these breathtaking beauties can be yours. Grow them in pots, and you can move them outdoors for the summer in many areas.
Here are 10 choices, all but one grown for their showy flowers over a long period, and one grown for its unusual leaves. Try one or two, and you may want to try more. See below for planting and care.
* Golden trumpet vine (Allamanda cathartica). This vine from the South American tropics bears 4-inch-wide sun yellow flowers at the branch tips. The funnel-shaped flowers are produced from summer to fall. This vine is easy and almost pest-free, perhaps because the leaves are poisonous. Left unchecked, it may reach 50 feet, but spring pruning can keep it within bounds.
* Bougainvillea. This vine, native to tropical South America, thrives throughout the tropics and subtropics and is probably the best known of the ones listed here. In cooler regions, it does well under glass and makes an especially spectacular pot plant outdoors in the summer and indoors when temperatures begin to fall. The inconspicuous flowers are surrounded by three brightly colored bracts in shades of red, pink, and purple as well as white, orange, yellow, and bicolored. Dwarf varieties, more suited to indoor cultivation, are also available, though they're not as spectacular. It is best to buy plants in flower, because nurseries often sell the same plants under different names. Some favorites are deep red 'Mrs. Butt' (similar to 'Crimson Lake') and 'Scarlett O'Hara' ('San Diego Red'), brick red 'Latertitia', pink-and-white 'Mary Palmer', orange-to-pink 'Miss Manila', double purple-red 'Mahara', and deep purple 'Sanderiana'.
* Cup and saucer vine (Cobaea scandens). This native of Mexico has 3-inch-long bell-shaped flowers with a green ruff at the base; they are greenish when they first open but change quickly to a beautiful violet-purple. In the tropics, plants can reach 40 feet, but pruning will keep the stems under control.
* Climbing lily or glory lily (Gloriosa superba 'Rothschildiana'). This tuberous perennial is not a true lily, despite its resemblance to the Turk's-cap lily (Lilium superbum). It climbs to 6 feet by tendrils at the ends of the leaves. The large eye-catching flowers 1 to 4 inches across are usually red and yellow and have six backswept, often crinkled, petals and protruding stamens. The stems (which die down in winter) grow from a tuber that should be planted on its side about 2 inches below the ground surface. Bloom time is summer to fall.
* Mandevilla. Among these natives of Central and South America are several conservatory and garden vines with dark green glossy leaves. M. laxa from Argentina has 2-inch white flowers on vines to 15 feet, while the somewhat larger flowers of M. 'Alice du Pont' and the Brazilian M. splendens are brilliant pink on 20- to 30-foot plants. A recent introduction called M. 'Tropical Delight' has bright yellow blooms. These plants grow well in pots in a greenhouse and flower over a long period. Mandevillas are related to Allamanda, and you can see the relationship in the mandevillas' similar but narrower flower shape. Nurseries often sell mandevillas as Dipladenia.
* Passion flower (Passiflora). Most people know blue passion flower (P. caerulea), which grows in temperate latitudes. The tropics, however, provide a wealth of other species that need warmer conditions. Some are far too large for the average garden, climbing by tendrils to 20 to 30 feet, but smaller, more manageable ones make ideal greenhouse plants. The fascinating flowers come in a range of colors from purple, pink, and white to scarlet and yellow, and vary from 1/2 inch to 6 inches across; most flower in summer. Some species, such as P. edulis, are grown for their fruit. Be warned -- growing passion flowers can be addictive, and before long you may find yourself building a collection that will take over your life. Try P. citrina, which bears abundant bright yellow flowers; P. phoenicia, with red and purple flowers smelling of fruit; P. quadrangularis, with very large flowers (about 5 inches across) in green, red, purple, and white; or P. vitifolia, with scarlet blooms.
* Flame vine (Pyrostegia venusta). Aptly named, this evergreen vine produces curtains of brilliant orange tubular flowers from fall to spring. This South American beauty climbs by tendrils to 30 feet or more but is easily controlled by pruning.
* Bridal wreath (Stephanotis floribunda). This native to Madagascar has thick dark green leaves and from spring to fall produces clusters of five-lobed waxy white flowers about 2-1/2 inches long. They are strongly fragrant and long-lasting and therefore a favorite for bridal bouquets. Vines can reach 10 to 15 feet.
* Thunbergia. Of the more than a hundred species of Thunbergia, only a few are cultivated. Probably the showiest is the sky flower (T. grandiflora), a vigorous plant from India. It reaches 20 feet (often more) and has large heart-shaped leaves. From summer to fall, it covers itself in hanging swags of mauve-blue flowers, each flower measuring about 3 inches across. T. g. 'Alba' has white flowers. Black-eyed Susan vine (T. alata) has twining stems and grows to about 6 feet. The flowers, 1 to 1-1/2 inches across, are usually bright orange with a black center, more rarely cream or yellow. It blooms throughout the summer, and if you live where winters freeze, simply treat it as an annual.
* Rex begonia vine (Cissus discolor). Some tropical vines are worth growing for their foliage, and this is such a plant. Although it's not related to the rex begonia, its leaves do look similar. The flowers are insignificant, but it is prized for its 4- to 6-inch-long deep green lance-shaped leaves conspicuously marked with silvery white (or sometimes pink) on the upper surface. The lower surface is deep red. It will climb a suitable support by means of its red tendrils. In a greenhouse, it can be trained as a spectacular ground cover, or allowed to hang from a basket, as well as being used as a conventional climber to brighten a dark corner. It is easily increased from cuttings.
Planting and Care
Start plants in pots suited to their size when you buy them, then move them to larger containers as they grow. Plant them in any good potting mix that drains well. At planting time, apply controlled-release fertilizer. If new growth yellows later in the season, supplement with any soluble fertilizer. Water before soil dries out completely, but not so often that plants get waterlogged.
Keep pots in a sunny position but watch that leaves of plants under glass don't get sunburned. During the summer, when nights are warm, pots can stay outdoors, but be sure to bring them in when nighttime temperatures are predicted to drop; bring them in for the winter well before the first frost date in your area.
Repot as needed, and prune off excess growth and errant shoots to keep growth within bounds.
Victoria Matthews, who lives in Denver, is a British botanist and garden writer with a special interest in vines of all kinds.