Begonias, with a variety of color and form, can be one of the showiest annuals for any shady garden. Tuberous begonias can produce single blooms that entirely cover the palm of a hand, while fibrous begonias exhibit delicate blossoms that will enhance any hanging basket or window box. Begonias can be divided into four types, classified by their root systems.
Begonia semperflorens varieties with their fibrous root systems are popularly known as Wax Begonias. These profuse bloomers have green, reddish or bronze foliage with masses if small flowers. They are the easiest begonias to keep in bloom indoors. Wax begonias do well in either full sun or semi-shaded areas. They are a good choice for borders or beds that are partially shaded by buildings or shrubbery.
Rieger Begonias (begonia X hiemalis) have a slightly swollen root stock. Their flower size is in between the fibrous and tuberous types. Bred as house plants, Rieger Begonias can continue to flower indoors under good light conditions in a bright window.
Rex Begonias spread via rhizomes which are not really roots, but thick stems which creep along the top of the soil. They are grown for their colourful, uniquely shaped foliage. Begonia Rex Varieties have dramatic, multicolored leaves. The iron cross begonia (Begonia masoniana) has a distinctive, dark, German-cross marking on green leaves.
Begonia X tuberhybrida varieties have large, fleshy bulb-like tubers; they are the largest, most colourful of all begonias. The large, male flowers bloom naturally during the long days of summer. Tuberous begonias are not usually grown indoors. However, you can buy tubers to start indoors—or outdoors after the frost-safe date.
Tuberous begonias are slow to root. Therefore, it is recommended to start tubers indoors 12-14 weeks before planting outdoors. Fibrous begonias are difficult to grow from seed, but if you want to try, allow 10-12 weeks before transplanting.
Transplanting should be performed 3 weeks after the last average frost. Space fibrous begonias 8 inches (20 cm) apart and tuberous varieties 10-12 inches (25-30 cm) apart.
Fibrous begonias can tolerate full shade to partial sun. Tuberous types prefer full to partial shade.
Begonias like cool, moist soil and they must be kept well watered.
Fertilizing can be performed biweekly in the summer months using Plant Prod’s Flowering Plant Fertilizer 15-30-15.
Over wintering Tuberous Begonias
Dig up and bring the tubers indoors after a light frost has killed the tops. Allow some soil to cling to the tuber. Dry thoroughly for a couple of weeks in a well ventilated area. At this point, the remaining soil on the tubers should easily break away. Store them at temperatures of 40-50° F (4-10°C) in peat moss or perlite. The tubers may be started indoors in late January to produce summer blooms.