By Charles T. Behnke, Ohio State University Extension
There are many tuberous types of begonias available today. Traditionally, we think of the large camellia flowered types with various color combinations grown from tubers. But also available are tuberous types grown from seed by specialty growers. These seed-started types are known as 'Nonstops'. Flowers are smaller but produced in profusion. Common to begonias is a soil mix with plenty of peat moss and perlite for good soil drainage. The tubers can be placed directly in pots or flats of a peat perlite mix and kept at 68 to 75 degrees F for sprouting to occur. Once the pink shoot starts to grow, keep plants in a sunny area. Plants should be kept evenly moist but not wet.
Fertilize every two weeks avoiding fertilizers with ammonia salt sources because crinkled and curled leaves can occur. Plants can be put outside in a semi-shaded location after all frost is past. Keep plants at the same level as they were in the original container, because burying stems deeper will encourage stem rot. Stake plants at time of planting. Water weekly by applying water directly on the soil to avoid wetting leaves and flowers. Fertilize on a biweekly basis with a liquid fertilizer. Larger male or center flowers will develop if the two side female flowers are removed as plants develop. Insect problems are minimal with begonias.
Diseases that can cause problems are powdery mildew, bacterial blight, botrytis and foliar nematodes. Culturally good plant spacing, removal of dead flowers and leaves, and adequate air movement should suppress disease problems. Bulbs can be saved from year to year. Remove stems after frost has killed tops. Let tubers dry for one week then store cleaned tubers in peat moss or sawdust at 50 degrees F. Do not allow tubers to freeze.