This group includes a number of perennials, mostly native to tropical forests of South America. All are grown for their colorful, showy, solitary or clustered flowers in the shape of tubes, trumpets, or bells. These plants require well-drained soil.
S. hybrids. Zones LS, CS, TS; USDA 8-11. Breeding work in recent years has produced a number of deciduous hybrids of complex parentage. Flowering stems of most are held well above foliage clumps. Examples include deep pink 'Arkansas Bells' (3 ft. tall and wide), light yellow 'Bananas Foster' (2 ft. tall and wide), mauve-pink 'Carolyn' (3 ft. tall, 2 ft. wide), peachy pink 'Georgia Peach' (15 in. tall, 1 ft. wide), and pink 'Pink Pockets' (just 10 in. tall, 2 ft. wide). All take moderate water.
S. sellovii. Zones LS, CS, TS; USDA 8-11. From Argentina. Upright stems are set with thick, light green, sandpapery leaves. Erect or nearly horizontal flower spikes are 2124 ft. long, each set with 100 or more small hanging flowers that resemble fuzzy orange or orange-red goldfish. Yellow and red forms are available. Beloved by hummingbirds. With age, develops a large tuber that tends to push above ground. Mulch any exposed part of the tuber well to protect it from temperatures below 25F. Give this plant plenty of room. Little to moderate water.
S. speciosa (Gloxinia speciosa). GLOXINIA. Indoor plant. Native to Brazil. Squat, full-foliaged plant to 1ft. high and wide. Broad, oval leaves reach 6 in. or longer, look like quilted green velvet. Blooms in summer, producing showy, velvety-sheened, ruffled bells up to 4 in. wide in a cluster near top of plant. Colors include white, red, pink, blue, and light to dark shades of purple. Some flowers have dark dots or blotches, others contrasting bands at edges. 'Carangola' is white with a deep blue-purple interior.
Gloxinias need constant warmth and are most often grown in a greenhouse or as houseplants, though they can be taken outdoors in warm weather. Tubers are usually available in winter or spring. For each tuber, choose a container big enough to leave 2 in. between all sides of tuber and container edges. Fill with a mix of equal parts peat moss, perlite, and leaf mold or compost; set tuber 12 in. deep. Place in a warm spot (about 72F during day, no cooler than 65F at night) with plenty of bright light but no direct sun. Water sparingly until first leaves appear, then increase watering as roots and leaves grow. Apply water to soil only, or pour it into a saucer to be absorbed through pot's drainage holes (pour off any water left unabsorbed after an hour). Feed with a general- purpose liquid houseplant fertilizer diluted to half-strength; start feeding when leaves emerge, then feed every two weeks until flowers fade. After bloom has finished, gradually dry off plants. When leaves have died down completely, move container to dark place where temperatures remain around 60F. Mist soil just enough to keep tubers from shriveling. When tubers show signs of resuming growth in midwinter, repot in fresh soil mix. If roots have filled container, move tuber to a larger pot.
S. tubiflora. HARDY GLOXINIA. Zones LS, CS, TS; USDA 8-11. From Argentina, Paraguay, Uruguay. As its common name suggests, this is a hardy perennial in much of the South. Growing from tubers, it forms 1- to 2-ft.-wide clumps of velvety green leaves to 5 in. long, 112 in. wide. Fragrant, tubular white flowers, 23 in. long, appear on spikes to 2 ft. tall throughout the summer. Needs moderate water and fertile, very well-drained soil. Excellent in a rock garden or large container.