The Hiemalis begonia (Begonia x hiemalis), a cross between a wax begonia and a tuberous begonia, is prized for its waxy green foliage and the brightly colored flowers that bloom profusely from spring until autumn. This sturdy, easy-care annual reaches heights of 10 to 12 inches, with a spread of 10 to 12 inches.
Reiger begonias need bright, indirect light year-round. They are photoperiod bloomers, meaning the bloom is stimulated by the number of hours of light they receive.
Use liquid fertilizer weekly at quarter strength or biweekly at half strength. In the fall, switch to a high-phosphorous fertilizer to encourage bigger blooms.
As old flowers are spent, pinch off the flowers to encourage new blooms to open. After the plant is done blooming, cut it back and let it dry out, then move it to a bright place and begin watering again when the weather warms up.
Reiger begonias need average to warm (and humid) temps. They can go as low as degrees Fahrenheit at night in the fall to help stimulate a bloom.