Begonias (genus Begonia) are attractive perennial herbs with soft, succulent stems, and white, pink, red, orange, or yellow flowers. Begonias are members of the begonia family, Begoniaceae, order Violales, subclass Dilleniidae, class Magnoliopsida (dicotyledons), division Magnoliophyta (flowering plants). The begonia family consists of five genera and 920 true species, the majority of which belong to the genus Begonia. Begonia taxonomy can be ambiguous, mainly due to the enormous number of horticultural varieties and hybrids, which many gardeners treat as species. These horticultural varieties of Begonia number in the thousands.
Begonia flowers are either staminate (male) or pistillate (female), and occur on the same plant, the plants being monoecious. Wild type flowers have four or five sepals, no petals, numerous stamens in males and an inferior ovary with three fused carpels in females. The colorful begonia sepals resemble petals, and plant breeding has produced many showy flower varieties. The begonia's fruit is a dry, winged capsule that splits lengthwise to release the seeds. Most begonias sprout easily from seeds and can also be propagated from leaves and stems. Leaves are simple and have wavy or serrated margins. Leaf arrangement on the stem is alternate. Two fleshy stipules occur at the base of the leaf petiole.
Horticulturists classify begonias into three categories based on rootstock: tuberous, fibrous, and rhizomatous. Unlike the tuberous and fibrous rooted begonias, which are cultivated for their flowers, rhizomatous
begonias are grown for their large, attractive foliage. The cultivated rex begonia, Begonia x rex-cultorum, is a rhizomatous begonia. This horticultural variety with beautiful foliage was developed in England from Begonia rex of India. Since most rhizomatous begonias originate from Brazil and Mexico, some people speculate that Begonia rex was also a cultivar. Rhizomatous begonias have striking foliage that takes many forms. Leaves can be hairy, fuzzy, or smooth, and are flecked with colorful patterns. Beefsteak begonia, Begonia feastii, is another example of a rhizomatous-rooted begonia.
The popular wax begonia, Begonia semperflorens, is a fibrous rooted begonia. Wax begonias are outdoor bedding plants that have smooth leaves and an abundance of flowers, hence the scientific name semperflorens, which means always flowering. Like the rex begonia, many colorful varieties of the wax begonia have been developed. The angel wing begonia, Begonia coccinea, with its thick, jointed stems, is another popular fibrous rooted begonia. Angel wing begonias have cane-like stems. Many cane begonias develop woody tissue in their stems.
Tuberous begonias such as Begonia x tuberhybrida, are best known for their showy flowers. They originate from South American begonias with large pink (Begonia boliviensis and Begonia veitchii) and yellow (Begonia pearcei) flowers. Cultivated tuberous begonias may resemble other popular flowers such as carnations and daffodils, and come in a range of sizes, including some varieties with large showy blossoms.
Begonias are indigenous to tropical and subtropical regions; no species is native to the United States. They occur primarily in Central and South America, Asia, and sub-Saharan Africa. The natural habitat of many begonias are moist, cool forests and tropical rainforests, but some begonias are adapted to dryer climates. Tuberous begonias are adapted to cool mountain habitats such as the Andes Mountains of Peru, where many horticultural varieties originate.
Although begonias are herbaceous perennials, they are susceptible to frost, and many varieties planted in the United States are treated as annuals. Begonias are easy to grow, both outdoors and in containers. They like bright light, not direct sun, a humid environment, and rich, aerated soil. Bright, indirect light is required to bring out the colorful patterns on rex begonia leaves. Begonias do best in mild temperatures (above 65°F [18°C] but can tolerate hot weather if they are kept in cool, shady places. Regular fertilization keeps plants lush and healthy.
Begonias are as easy to propagate as they are to grow. Plant seeds in rich, well-drained soil, such as African violet soil, and keep them protected. Many growers propagate plants from stem and leaf cuttings. Leaves are cut into wedges, each wedge with a central vein. The wedges are dusted with rooting hormone and planted in builders sand. The developing leaf wedges are given high humidity, bright indirect light, and occasional waterings. New shoot growth appears in two to three months. Cane and rhizomatous begonias may also be propagated from stem cuttings.
Begonias are susceptible to mealybugs and aphids, controllable with insecticidal soaps. Rex begonias may be infected with nematodes, soil-dwelling plant parasites that are more difficult to treat. Many garden shops carry products to control nematodes. A home remedy for these pests is mothballs. Watering the plants with mothballs on the soil surface will help eliminate the nematodes.
Because of their success and popularity as ornamental bedding and container plants, begonias are economically important.
The American Horticultural Society. The American Horticultural Society Encyclopedia of Plants and Flowers. New York: DK Publishing, 2002.
Heywood, Vernon H. ed. Flowering Plants of the World. New York: Oxford University Press, 1993.
Carlquist, S. "Wood Anatomy of Begoniaceae, with Comments on Raylessness, Paedomorphosis, Relationships, Vessel Diameter, and Ecology." Bulletin of the Torrey Botanical Club 1985.
Martin, T. "Rex Begonias." Horticulture (January 1988).
Neuman, L. "Top-notch Tuberous Begonias." Horticulture (July 1988):18-23.
Elaine L. Martin