Tropical, typically twining plants noted for showy flowers. Some grow fast enough to bloom the first season and can be treated as annuals. Those grown as perennials are evergreen in the Tropical South. Provide rich, well- drained soil. Good greenhouse plants.
T. alata. BLACK-EYED SUSAN VINE. Perennial vine grown as annual. May live over in Zones CS, TS; USDA 9-11. From Africa. To 10 ft., with triangular, 3-in., medium green leaves. Blooms all summer long; tubular flowers flare out to 1 in. wide, come in orange, yellow, or white, all with purple-black throat. Start seed indoors; set plants out in good soil in a sunny spot as soon as weather warms. Display in hanging basket or window box, use as ground cover, or train on strings or low trellis.
T. battiscombei. BLUE CLOCK VINE. Vining shrub. From Africa. Unless given support, it forms a mound 46 ft. high, 68 ft. wide. Scrambling stems bear broadly oval, glossy, bright green leaves to 7 in. long. Fuzzy greenish white buds appear in leaf joints; from spring into fall, these open to 2- to 3-in.-long, yellow-throated flowers in an intense blue-purple. Top dies back in cold weather, but roots are hardy to 20F.
T. erecta. KING'S MANTLE. Vining shrub to 6 ft. tall and wide. Native to Africa. Erect, sometimes twining, with dark green, ovate to oblong leaves to 3 in. long. Velvety dark blue, 3-in.-long flowers with orange or cream throats resemble those of gloxinia (Sinningia); they appear in joints of upper leaves throughout summer and fall. 'Alba' is a white-flowered form.
T. fragrans. SWEET CLOCK VINE, WHITE LADY. Perennial vine. Native to India. Woody, twining stems reach 810 ft. high, set with notched, oval green leaves to 3 in. long. Lightly scented summer flowers to 3 in. across appear singly or in clusters; white is the usual color, but blossoms may be blue, lavender, or even yellow. Prune this vine regularly, or it may get away from you.
T. grandiflora. SKY FLOWER. Perennial vine. From India. Vigorous growth to 20 ft. or more, with 8-in., heart-shaped, medium to dark green leaves. Slightly drooping clusters of tubular, flaring, sky-blue flowers to 3 in. across appear from late summer through fall. Use on arbor, large trellis, or wire fence; casts dense shade. 'Alba' has white flowers.
T. gregorii. ORANGE CLOCK VINE. Perennial vine; grow as summer annual outside Tropical South. Native to Africa. Showy and easy to grow; twines to 6 ft. high or sprawls over ground to cover a 12-ft. circle. Gray-green, triangular, tooth-edged leaves to 3 in. long. Tubular, flaring, bright orange, 3-in. flowers are borne singly on 4-in. stems. Blooms nearly all year long in the Tropical South, in summer elsewhere. Set plants 34 ft. apart to cover a wire fence, about 6 ft. apart as ground cover. Plant above a wall and let stems cascade down; or grow in hanging baskets.
T. mysorensis. INDIAN CLOCK VINE. Perennial vine. From India. Climbs to 1535 ft., with narrow, elliptical, dark green leaves up to 6 in. long. Spectacular, pendent, 1- to 112-ft.-long clusters of gaping, 2-in.-long flowers that are red on the outside, yellow within. Blooms much of the year, most heavily in spring. Train on pergola, arbor, or other overhead structure to permit flowers to dangle. Protect from frost.