Although many begonias are grown as bedding plants to add bright color with their non-stop blooms, rex begonias are typically grown for their striking foliage. These impressive plants produce a variety of multi-colored leaves that may grow to sizes of a foot or more. In hanging baskets, rex begonias create a striking show of foliage with less significant blooms than other begonia varieties. The key to success with rex begonias is providing proper lighting, regular watering and occasional fertilizer.
Plant rex begonias in lightweight soil, as they suffer in heavy soils. Mix all-purpose potting soil with equal parts perlite or vermiculite and peat moss to create your own soil mixture.
Check pots and containers for drainage holes. Drill holes in the bottom of pots or containers that do not have adequate drainage. Drill five or six 1/4 to 1/2-inch holes evenly spaced around the lower side of the pot, about 1/2 inch from the bottom.
Layer the bottom of the pot with 1 inch of gravel or pebbles to promote drainage. Fill the pot three-fourths full of potting mixture. Place the begonia plant in the pot, and fill in around the roots with soil. Firm down to secure the plant.
Water thoroughly until water runs freely from the bottom of the pot. Allow the soil to dry slightly before watering again. Rex begonias prefer slightly dry soil and suffer if over watered. Watch for signs of wilting, and adjust water accordingly.
Place the pot in an area that receives indirect light. If planted outside, rex begonias thrive with filtered morning light and afternoon shade. Direct sun burns foliage and stresses these low-light plants.
Maintain daytime temperatures between 66 and 73 degrees Fahrenheit for begonias grown in the home. Nighttime temperatures should not drop below 55 degrees Fahrenheit. If growing rex begonias outside for the summer, move them inside before temperatures begin to drop at night.
Apply water-soluble fertilizer for houseplants, mixed to half strength, every two weeks during periods of active growth. Reduce to once per month during the winter months when growth slows. Resume fertilizing again in spring when a flush of new growth appears.