Widely grown for showy flowers, the genus Mandevilla includes plants formerly called Dipladenia. They thrive in warm, humid weather and bloom continuously from late spring to frost in most areas of the South. They are generally hardy outdoors in the Coastal and Tropical South; elsewhere, they can be overwintered indoors or treated as annuals. Blossoms consist of five broad lobes that flare out from a tubular throat; except as noted, they are unscented. Plants climb by twining. Use them to cover arbors, trellises, and fences. Excellent container plants. Plant in fertile, well-drained soil. Provide protection from hottest afternoon sun. Feed with a balanced, water-soluble fertilizer every 2 to 3 weeks throughout the growing season. Growth may need thinning from time to time. Watch for spider mites.
M. boliviensis. Evergreen. Zone TS; USDA 10-11. Native to Ecuador and Bolivia. Grows to 12 ft. as a vine; reaches 3 ft. tall and 5 ft. wide as a sprawling shrub. Glossy, oval, pointed leaves to 4 in. long; 2-in.-wide white flowers with golden-yellow throats.
M. hybrids. Evergreen. Zone TS; may grow as root-hardy perennials in Zone CS; USDA 9. The hybrid mandevillas described here are sometimes sold as selections of M.xamabilis or M.xamoena. Plants grow to 1520 ft., with glossy, dark green, oval leaves 38 in. long. Most widely grown is 'Alice du Pont', with clusters of glowing pink, 2- to 4-in. flowers appearing among the leaves; even very small plants in 4-in. pots will bloom. 'Moonlight Parfait' is a vigorous grower; pink buds open to large white blossoms with a double-petaled pink center. 'Summer Snow' ('Monte', 'Flora Snow') bears blush-pink blossoms that eventually fade to white. 'White Delight' has pale pink buds opening to white blooms with a light yellow throat. 'Ruby Star' is a slightly more compact plant with narrower-lobed, 3-in.-wide flowers; blossoms open deep pink, then mature to magenta with a touch of yellow deep in the throat. 'Rita Marie Green' ('Pink Parfait') has long-lasting, hot pink, double flowers; 'Tango Twirl' offers upright clusters of light pink, double blooms. The Sun Parasol series blooms at a young age and is available in shades of red, pink, and white. Plant all hybrids in rich soil and provide a frame, trellis, or stake for support. Pinch tips of young plants to induce bushiness.
M. laxa (M. suaveolens). CHILEAN JASMINE. Deciduous; evergreen in frost-free areas. Zones CS, TS; USDA 9-11. Native to Chile and Argentina. Grows to 15 ft. or more, with heart-shaped, 2- to 6-in.-long leaves. Clustered flowers are white, 12 in. across, with a powerful perfume like that of gardenia. Requires less heat to bloom than other mandevillas. Provide rich soil. If plant becomes badly tangled, cut to ground in winter; it will resprout and bloom on new growth. Roots are hardy to about 5F.
M. sanderi (Dipladenia splendens). BRAZILLIAN JASMINE. Evergreen. Zone TS; USDA 10-11; may grow as root-hardy perennial in Zone CS; USDA 9. Native to southeastern Brazil. Compact, shrubby plant to 2 ft. tall, 3 ft. wide; eventually starts to twine (to 1520 ft. tall with support), but you can keep it bushy by pinching climbing shoots. Deep green leaves are 48 in. long, tinged with bronze when new. Flowers are 34 in. wide, rose-pink with yellow throats; color fades as blossoms age. 'Red Riding Hood', with deep cherry-red flowers; white-blossomed 'Faire Lady' ('My Fair Lady'); and scarlet 'Scarlet Pimpernel' are lower growing and shrubbier than the species (to 68 ft. as climbers) and superb in hanging baskets. Similar in form is 'Strawberry Lemonade', with deep pink, yellow-throated flowers; its leaves are beautifully variegated in mint-green, cream, and white, with pink flushes when young.