First, you must understand that "begonia" is not one plant with a single need. We are a vast and diverse genus with over 2,000 species and countless hybrids. Our sunlight requirements vary dramatically based on our ancestry and the characteristics we've developed. Treating us all the same will lead to some of us struggling. The key is to observe our foliage.
Indoors, our needs are primarily dictated by our leaf type. We communicate our comfort through our foliage.
For fibrous-rooted begonias (e.g., wax begonias, angel-wing begonias): We generally enjoy bright, indirect light. A spot near an east-facing window is ideal, where we receive gentle morning sun. A west-facing window can also work but may require a sheer curtain to filter the stronger afternoon rays. Our leaves will tell you if we're happy: they will exhibit vibrant colors and steady growth without any signs of scorching.
For rhizomatous and rex begonias: We are the shade-lovers. Our intricately patterned and often darkly pigmented leaves are easily scorched by direct sun. We thrive in medium to bright indirect light. North-facing windows or positions further into a room away from a south or west window are perfect. Too much light will cause our beautiful colors to fade and our leaf edges to turn crisp and brown.
Outdoors, the intensity of the sun is greater, so our placement requires more careful consideration. The general rule for most of us is dappled sunlight or partial shade.
Ideal conditions: Imagine the light pattern under a tree with light foliage. This mimics our natural, forest-floor habitat. Four to six hours of morning sun is often perfect, as it is less intense than the afternoon sun. This provides us with the energy we need to flower and maintain strong growth without the stress of overheating.
Tolerance variations: Wax begonias (Semperflorens group) are among the most sun-tolerant. We can handle more direct sun, especially in cooler climates, but even we appreciate relief during the hottest part of the day. In contrast, rex and tuberous begonias are much more sensitive and must be protected from any harsh direct afternoon sunlight to prevent leaf damage.
Please watch for these signals, as they are our way of asking for help.
Too much sun (scorching): You will see leaves turning pale, yellowish, or developing brown, crispy patches and holes. Our growth may become stunted, and we may drop leaves or flowers to conserve energy. We are essentially getting a sunburn.
Too little sun (etiolation): If we are not receiving enough light, we will become leggy and stretched, with large gaps between our leaves as we desperately reach for a light source. Our growth will slow significantly, our leaves may become smaller, and we will likely refuse to produce any flowers. Our vibrant leaf colors will often fade to a dull green.
