Growing Instructions for Tuberous Begonias:
Begonias should be planted with 1 to 1.5 inches of soil covering the top of the tuber, in well-draining beds or large pots. Partial shade is necessary in all but the coolest climates, although begonias do need at least some sunlight. An Eastern exposure is also acceptable, receiving full sun in the morning with afternoon shade. Any light soil is satisfactory. Humus such as peat moss or leaf mold is good for retaining moisture and creating slightly acid conditions. Begonias need to be moist at all times. Any mild fertilizer can be used at intervals throughout the season. A natural fertilizer such as fish emulsion is ideal. For best results, fertilize lightly in the first few weeks of growth, as this will promote earlier bloom. Increased nitrogen after blooming begins will help maintain greener foliage.
Tubers may be planted directly in pots or started as above. Pots should be at least 6 inches in diameter. Any good potting mixture will serve, or and humus and sand for good drainage to any suitable loam soil. Bright, indirect light is necessary and cool temperatures are required.