Culture
Grow in well-drained, humusy soil in bright light but not too much direct sunlight. Water regularly when growing actively but reduce watering in winter or when plant growth is slow. Wet soil, especially cold wet soil, can lead to root and stem rots. Many rhizomatous begonias are suitable as indoor plants and others do well as summer bedding plants. Hardy in Zones 10-11.
Noteworthy Characteristics
Begonia is a genus of about 1,300 species of annuals, perennials, shrubs and climbers. Most have fleshy stems. Some produce underground tubers or rhizomes. They are grown for their showy flower or colorful leaves; some for both. Begonias can be divided into 7 informal groups by growth habit: cane-like, rex-cultorum, rhizomatous, semperflorens, tuberous, trailing or scandent, thick-stemmed and shrub-like.
Rhizomatous begonias feature a compact, mounding habit with the foliage emerging from thickened rhizomes that grow along the soil surface. The leaves can be quite showy and come in numerous colors, shapes, and textures. The flowers are typically white or pink and held in airy clusters above the foliage.
Genus name honors Michael Begon (1638-1710), Governor of French Canada.
'River Nile' is a hybrid rhizomatous begonia selection that features chartreuse to lime green, spiraled leaves with dark red-brown, ruffled margins. The hairy leaf stems are succulent and pale yellow in color with contrasting red flecks. The leaves emerge from fleshy rhizomes that sit at the surface of the soil. Airy clusters of small, white flowers bloom seasonally. Mature plants can reach up to 2' tall with a similar spread and take on a dense, mounding habit.
Problems
Susceptible to bacterial leaf spot, powdery mildew, botrytis, and stem rot, especially in humid conditions with poor air circulation. Watch for mealybugs and thrips.
Uses
Suitable for massing in beds, borders, and as an edger. Use in containers, hanging baskets, and window boxes. Most are also suitable for use as houseplants.