Growing a Rex Begonia Indoors Growing a Rex Begonia Indoors

Grown more for its spectacular and colorful foliage than for its blooms, rex begonia is one of the showplace plants in the begonia world. Although the plant will bloom, its flowers pale in comparison to the leaves, which come in every color, shade, pattern, shape and size. Growing a rex begonia indoors requires an understanding of the conditions and maintenance they need.

Rex Begonia Facts

According to the American Begonia Society, all types of the Rex cultorum, or rex begonia, are descendants of the Indian species first introduced to cultivation as B. rex in the 1850s. Hybridizing resulted in numerous cultivars that make the rex begonia a popular indoor plant. Most of the rex begonias grow from a thickened stem called a rhizome. They are not, however, classed with the other rhizomatous begonias because of their colorful, bold leaves and more stringent growing requirements.

This is exactly what makes the rex begonia so desirable for growing indoors. Leaves are widely varied and may display stripes, borders, spots or splotches of various colors.

Favorable Growing Conditions

Some rex begonia varieties branch out and are more upright, while others are compact and creeping. It’s important to note that they are not easy-care plants for growing indoors. They like much more humidity than many other indoor plants, 50 percent humidity or more, depending on variety. They also require a shallow pot due to the short root stalks, porous planting mix, heavy fertilization during the early growth period, and constant attention to watering. More rex begonias are killed through overwatering than under watering. As a general rule, allow the soil to become almost completely dry between watering.

TIP: Our expert gardening advisor, Susan Patterson adds, "Rex begonias grow very slowly and should not require re-potting for many years."

Best Indoor Location

First of all, avoid placing your begonia in the kitchen. The extremes of temperature with ovens, ranges and opening and closing of the refrigerator are simply not conducive to the high humidity the rex requires. Make sure the location gets plenty of indirect light. In cooler areas, morning sun or filtered sunlight may work well. Be sure to rotate the plant if light only hits one side of the plant.

Many gardeners who specialize in growing rex begonia place the plants in a shadehouse, bathhouse or greenhouse.

Rex begonias like daytime temperatures hovering near 70 degrees. At night, no lower than 60 degrees is advised. Cooler temperatures may cause the rex to grow more slowly.

Adequate Humidity

In a greenhouse, shadehouse or bathhouse, and when growing multiple containers of rex begonia, you can place the containers on benches above a bed of gravel. Water the gravel and, as the location warms up, the humidity will increase. Inside the home, a similar condition can be achieved by placing the pot in a tray lined with gravel. A humidifier can also provide adequate humidity for the rex.

TIP: Susan advises, "If leaf tips turn brown the humidity may be too low."

Fertilizing

In springtime, when new growth is beginning, begin with a balanced fertilizer (14-14-14 or 20-20-20). Then switch or alternate with 15-30-15 or similar. Continue regular feedings through the summer, tapering off in late summer when growth slows.

Keep the rex well groomed by removing dead leaves and blooms and keeping the planting mix surface free of debris. With a little practice and patience, rex begonia will soon reward the home gardener with a spectacular show of foliage.

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