Well, there are several types of begonias you can grow indoors, all of them very different from one another in the way they look and grow, and all with their own special virtues. The fibrousrooted wax begonias, which are normally grown most often as outdoor annuals, make fine ever blooming houseplant. Tuberous begonias also can be grow9n as houseplants though they will only bloom in summer Angel-wing begonias (Begonia coccinea) are fribrous rooted, cane type begonias that grow up to 4 feet and more and bear dangling clusters of small are flowers almost year round. Iron cross begonias “B. masoniana” are foliage plants, growing 1 ½ feet tall from rhizomes; they are valued for their crinkly, apple green leaves, which are marked in the center with a dark green cross.
Perhaps the most spectacular and popular begonias grown as houseplants are rex and Rieger begonias. Rex begonias “B. rex-cultorum” grow from rhizomes and have small pink or white flowers in spring, but heyare most prized for their arge magnificent leaves, which are an intricate brocade of green, red, bronze, pink or silver. They make a lavish mound a foot tall or a bit more miniature varieties are 6 to 8 inches. Rieger begonias “B. x hiemalis” often have colored leaves but are grown for their profuse, showy flowers at least 2 inches across in shades of red, pink, orange and yellow. Which provide months of color in winter? They are fibrous rooted.
Begonias in general like plenty of light, and flowering types should have several hours of sun each day for best winter bloom. Daytime temperature should be in the 65- to 75- degree range a bit cooler for Rieger begonias and not below 50 degree at night. All especially rex begonias like humid air, but it must circulate well to avoid mildew, especially the large leaved types.
Soil with should be a nice, light, organic mix, like that sold for African violets, and should be kept evenly moist, or just slightly dry between watering. But drainage must be excellent and you should avoid wetting the leaves. Fertilize lightly with a balanced fertilizer about every two weeks, while plants are in active growth or in the case of Rieger begonias, all year. Fibrous rooted kinds should be repotted in spring as needed; those with rhizomes go in shallow pots and should remain rootbound until you can see rhizomes all over the soil surface.
Moreover Rieger begonias that stop blooming can be cut back to several inches to produce fresh, flowering growth. Stems of rex begonias should be cut back to the base if they start to get leggy. Wax begonias also benefit from being cut back, and stems of angel wing begonias without leaves should be cut back in early spring to make new growth. All begonias can be propagated easily by stem cuttings. With rex and Rieger begonias leaf cutting are also a good method.