Although they are mostly gown as an outdoor shade plant, begonias can also make beautiful houseplants. Many begonia types have attractive, colorful leaves, so even if they don’t flower indoors in winter, they will still look interesting. While you can overwinter the common wax-leaf begonias, there are others that make better houseplants. The rhizomatous begonias, such as ‘Last Laugh’ and ‘Black Coffee’, have small rhizomes that creep along the soil surface. They tend to flower in winter, producing white or pink blooms. Place these plants in a brightly lit room, keep the soil slightly moist, and lightly fertilize in winter. The Cane or Angel Wing types are common plants. They tend to have large, colorful leaves. Like the rhizomatous types, they need bright indirect light and slightly moist soil to grow well.
The Rex begonias such as ‘River Nile’ and ‘Fire Flush’ do require a little more care to keep them looking their best indoors. They have amazingly diverse colored and textured foliage, but require high humidity, the right soil moisture, and bright light to survive. However, don’t overwater your plants or they may get root rot. Let the leaves show signs of drooping before watering. It’s best to grow these under fluorescent lights. Mist them daily, place a humidifier close by, or cover the light setup with a clear plastic tent to maintain high humidity in winter.
Tuberous begonias would be a great challenge indoors. It would be better to just store the bulbs in a cool, dark location over winter and repot them in spring to grow in pots outdoors in summer.
Another place to grow begonias to keep the soil moist and humidity high is in a terrarium. Select small varieties that will fit easily in your bowl.
In addition to keeping the soil moist, the humidity high, and the room brightly lit, watch for insects such as mealybugs. Control mealybugs on the stems and leaves by dabbing them with a cotton swab dipped in rubbing alcohol. Don’t wet the leaves when watering, as this can spread powdery mildew disease on the plants.