Soil/pH:
Hiemalis Begonias perform best when grown in a fast-draining, well-structured medium with sufficient peat moss for water retention. A mix of 70% peat moss, 30% perlite provides an ideal medium for optimal growth. Pasteurize the medium at 180 degrees Fahrenheit for 30 minutes. Supplemental superphosphate and micro-nutrients must be added to avoid any nutrient deficiencies. For a soilless mix, adjust the pH to 5.5-6.0 by the addition of dolomitic limestone.
When rooting, the top of the young starter plant root ball should be planted ¼" above the surface of the growing mix to aid in prevention of stem rot.
Temperature:
Optimal temperature for Begonias to develop lush vegetative growth is 70-72ºF with a 14-hour or longer day. After desired plant size is reached, the temperature should be lowered to 65ºF with a 12-hour or shorter day. The lower temperature aids in flower initiation and provides deeper bloom color, better bloom production and an overall sturdier plant. Final development can be delayed by reducing the temperature as low as 62ºF. Air-cooled houses may be necessary in warm regions during summer production. Temperatures over 75°F will result in soft growth and flower delay.
Carbon Dioxide:
Supplemental CO2 benefits plants grown in low light areas by better utilizing the limited daylight, providing faster growth, flowering and overall plant quality. CO2 will increase photosynthesis when used at 1,000-1,500 ppm during daylight hours. When growing at higher CO2 levels, greenhouse day temperature should be 5-10ºF degrees warmer.