Culture
Tender perennial that is winter hardy to USDA Zones 10-11. In St. Louis, it is grown as an annual. 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 such as St. Louis. Bronze-leaved varieties are more tolerant of full sun. Plants tolerate considerable shade, but are generally less floriferous with less sun. Plants are best with consistent moisture throughout the growing season, but tolerate periods of drought due to their thick and waxy leaves which help minimize water loss in hot weather. Start seeds indoors 6-8 weeks before last frost date, purchase starter plants or take cuttings from overwintered plants. Set plants out after last frost date. Space plants well (8” for dwarfs and 12” for taller ones) to promote good air circulation and to reduce potential fungal disease problems. Container plants may be cut back in fall and overwintered indoors a cool location with reduced watering. Propagation from seed can be difficult due to the small size of the seed, and seed should not be sown directly in the garden.
Noteworthy Characteristics
Begonia × semperflorens-cultorum is a name applied to a group of cultivated, hybrid begonias commonly called wax begonias. These are compact, bushy, mounded, fibrous-rooted plants that feature fleshy stems, waxy dark green to bronze leaves and loose clusters of single or double flowers. The flowers come in shades and bicolor combinations of white, pink or red. Blooms reliably throughout the growing season. Dwarf varieties grow to 6-8” tall and taller varieties grow to 10-12” tall.
Genus name honors Michael Begon (1638-1710), Governor of French Canada.
The hybrid name semperflorens-cultorum is a combination of semperflorens meaning "always in flower" and cultorum meaning "of cultivated origin".
The common name wax begonia refers to the waxy texture and appearance of the leaves.
'Harmony Scarlet' is a hybrid wax begonia selection that features dark leaves, red flowers, and a compact, mounding habit. Mature plants will reach up to 8" tall with a similar spread.
Problems
Susceptible to powdery mildew, botrytis, and stem rot, especially in humid conditions with poor air circulation. Watch for mealybugs and thrips.
Uses
Suitable for use in beds, borders, and as an edger. Use in containers and window boxes.