Let’s take a look at the most critical elements of growing the rex begonia as houseplants.
Growing Rex Begonias Indoors
Rex begonias are rhizomatous begonias. A rhizome is basically a thickened stem, and the leaves emerge from the rhizome. Generally, the rex begonia indoors prefers relatively cool temperatures, moist soil, and humid conditions. Rex begonias do well in bright indirect light. Some direct sun is okay for short times, especially if it is from an eastern window that has morning sun, which is gentler. For periods of the year where the sun is strongest, or if you live in an area that has strong sun, you will want to avoid too much direct sun. You can easily use sheer curtains to diffuse direct sun, or set the plant a few feet back from a very sunny window. Too much direct sun can burn the foliage. Rex begonias prefer to grow in a fairly evenly moist soil. However, you must have a good balance because these plants can easily be prone to root rot. A good rule of thumb is to allow the top inch or so (2.5 cm.) to dry out, then water again. It is better to keep the soil on the slightly drier side, but never let the soil completely dry out, as this can quickly spell death for your rex begonia. If you let the soil get too dry, your plant will quickly wilt. As far as fertilizing goes, you can fertilize with a dilute solution about twice a month during the active growing season. Avoid fertilizing during the winter months when plant growth can come to a halt. Also, avoid allowing your rex begonia’s leaves to be wet for extended periods of time, especially at night, since this can encourage powdery mildew as well as bacteria leaf spot. As far as soil goes, rex begonias like a light and airy soil. Avoid any heavy potting mixes. Potting mixes designed for African violets are a good choice for rex begonias. Rex begonias like conditions with high humidity. In fact, the foliage will grow larger when the humidity is higher. Aim to increase the humidity, especially during the winter months, by a few different methods. You can place a plant on a tray with wet pebbles, use a humidifier, or place them in naturally humid areas such as a bathroom. You can also group plants together to increase humidity through plants’ natural process of transpiration. Finally, choose a pot that is wider than it is deep since this is more appropriate for rhizomatous plants like rex begonias. If you’d like to propagate them, you can do so by leaf cuttings or by cutting sections of the rhizome and repotting.
