Irrigation/Nutrition Growing Period:
Hiemalis Begonias are not heavy feeders. For optimal vegetative growth constant feed at 100-150 ppm N, 50 ppm P, and 100-150 K is recommended. Continue at this rate through week three of short-day treatment. It is essential during the first 10 days to keep the medium moist, not soggy or dry, in order to obtain maximum root growth. Watering should be done in the morning hours to aid in disease prevention, preferably with a tube watering system. Grow on open benches and keep the foliage dry. Be careful to avoid soluble salt buildup; Begonia roots are very salt sensitive.
Flower Initiation:
During the fourth week of short-day treatment, apply only clear water. The fifth week after the start of short-day treatment, fertilizer should be resumed but at a rate of 100 ppm N, 50 ppm P, and 150 ppm K. Continue to alternate one clear watering to one feed application. Overfed plants with crisp, lush green foliage do not produce as many flowers as plants kept slightly hungry during flower development.
Lighting Long-Day Treatment:
During the vegetative growth period, interrupted or supplemental lighting may be necessary to maintain a 14-hour day length. Lighting Begonias is intended to encourage growth, not delay flowering, as they are only slightly photo periodic. Lights should be applied to extend the day length. In the northern latitudes supplemental lighting is recommended from September 1 to March 31. Under low-light conditions Hiemalis Begonias require additional lighting to prevent growth standstill until short-day treatment begins. Interrupted lighting of 50% on and 50% off will suffice. Light for three extra hours daily during months of September, October and March; four hours in November and February; and five hours daily in December and January. Twenty to 50 f.c. of incandescent light is recommended. Be careful not to expose Hiemalis Begonias to extremely high daylight intensities. During high-light periods apply shade to prevent leaf sun scald and vegetative hardening. The amount of light that can be tolerated depends on temperature. Begonias can be safely exposed to 3,000 f.c. at 70ºF or below, 2,000, f.c. at 80ºF and 1,500 f.c. at 90ºF.
Short-Day Treatment:
Short-day treatment begins when the desired number of shoots have emerged and sufficient new growth has developed. Since Hiemalis Begonias are only slightly photo periodic, short-day treatment is basically provided to produce shorter, more compact plants; and develop uniform flowering. The older the plant the more readily it will produce flowers, even under long day lengths. The number of flowers and flower buds will be at their peak when the day length is reduced to 10 hours and the temperature is reduced to 64ºF. Plants grown in longer day lengths appear to have more vegetative growth at the expense of flower development. Four weeks of short-day treatment (maximum 12-hour day length) is necessary for good flower initiation. During periods of high temperature, black cloth material should be applied at 7 p.m. and removed at 9 a.m. to prevent heat buildup.