University of Illinois Extension

Rex Begonia

Consider using plants with colorful variegated foliage indoors this winter, Jennifer Schultz Nelson, a University of Illinois Extension horticulture educator, recommended. “Variegated plants generally need more light than plants with solid green leaves,” said Schultz Nelson. This additional light is required for the variegation to develop. Even though they need more light, typically they need far less light than most flowering plants do.”

One group of plants with an incredible level of diversity in foliage color and pattern is the rex begonia. These plants are grown specifically for their foliage. They do flower, but the flowers are usually not very showy.

“Though they may lack showy flowers, Rex Begonias make up for it several times over with their gorgeous leaves,” she said. “They may be bumpy or smooth, streaked with colors such as white, pink, yellow, or purple, and come in as many shapes as you can imagine.”

Many articles classify Rex Begonias as “difficult” or “fussy” plants, but don’t let this scare you from trying to grow them. Their colorful displays make the extra care worthwhile. And the extra attention will likely benefit your other plants as well.

“The big “extra” that Rex Begonias need is humidity,” she noted. “Crispy brown edges on the leaves are usually a sign that the humidity is too low. Generally, Rex Begonias need in excess of 50% relative humidity. This can be hard to achieve in homes during the winter.

“One way to increase humidity is by placing your begonias on trays filled with water and pebbles, without the water actually touching the pots. Running a humidifier in the room is another option, one that will probably benefit your other houseplants, as well as the human residents of your home!”

While they thrive in high humidity, begonias will not tolerate wet feet. In fact, if kept wet too long, they will probably succumb to mildew and botrytis, both fungal diseases related to excessive moisture which turn your plant into a mushy rotten mess.

“Two ways to counteract overwatering is to make sure there is good air circulation around your plants, and use a potting mix with excellent drainage,” she said. “Also strive to avoid “calendar watering”—watering on a strict schedule. Learn to inspect your plants and assess whether they need water, no matter what the calendar says. In general, the top of a Rex Begonia’s soil should just begin to dry out before watering again.”

Rex Begonias need bright, but indirect light. Direct, hot sunlight will bleach out their brilliant colors. Morning or late afternoon filtered sunlight is acceptable. Rex Begonias need temperatures higher than 60 degrees and thrive at temperatures around 70 degrees during the day. Rex Begonias are relatively slow growers, but benefit from using a balanced fertilizer during the growing season to maximize color development in the foliage.

“With a little effort Rex Begonias will brighten even the dreariest winter day,” Nelson said. “Most people find it hard to stop at owning just one Rex Begonia when they realize how many beautiful choices are available.”