These Begonias grow best in bright indirect sunlight coming from a south, east or west window. Fluorescent grow lights are also an excellent alternative to natural light for these plants. When potting, set the plant with the crown slightly above the soil line. They should be planted in a porous, slightly acidic planting mix that contains some peat moss and leaf mold. African Violet potting mixes work well for Begonias.
Using room temperature water, keep the soil evenly moist (never soggy) when the plants are actively growing, but allow the soil to dry slightly between waterings when growth slows.
Keep water off of the foliage to help avoid powdery mildew and possible crown rot. Never allow your plant to stand in water. Feed actively growing plants every two weeks with a fertilizer formulated for house plants, applied at the recommended rates. Iron Cross Begonias thrive with daytime temperatures of 70° and 60°-65° at night. They will perish at temperatures below 55° Provide additional humidity by setting the plants on shallow trays filled with moistened pebbles, especially during the winter months.