Culture
Tender perennial that is winter hardy to USDA Zones 10-11. In St. Louis, it is grown as an annual or houseplant. It is noted for its tolerance to hot and humid summers. It is easily grown in average to moderately fertile, moist, well-drained soils in full sun to part shade. Prefers sun dappled part shade and a good mulch in hot summer climates. Plants tolerate considerable shade, but are generally of more open form and less floriferous therein. Plants are best with consistent moisture throughout the growing season, but allow soils to dry between waterings. Plants tolerate periods of drought due to their thick leaves which help minimize water loss in hot weather. Purchase starter plants or take cuttings from overwintered plants. Set plants out after last frost date. Space plants well to promote good air circulation and to reduce potential fungal disease problems. Container plants may be cut back in fall and overwintered indoors in a cool location with reduced watering. Plants can also be grown and overwintered as houseplants in a warm and bright location.
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.
Rex-cultorum Group, commonly called rex begonias, are mainly evergreen begonias resulting from crossing Begonia rex with other species. They are usually rhizomatous and can vary in size and habit. They are grown primarily for their showy foliage.
Genus name honors Michael Begon (1638-1710), Governor of French Canada.
'Green Gold' is a hybrid rex begonia selection that features colorful, spiral leaves. The silvery leaves have jagged margins and prominent veins highlighted with dark green and red. The new foliage emerges with a slightly golden yellow hue before maturing to silver. Mature plants will reach up to 1' tall and 1.5' wide. Grown for the foliage rather than the small, pale pink blooms.
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. Overwintered plants may lose their foliage and go dormant until spring.
Uses
Containers, hanging baskets and window boxes. Annual for beds, borders and foundations. Houseplant.