From our perspective as plants, sunlight is not merely a preference; it is the very currency of our existence. We convert this radiant energy into chemical energy through the miraculous process of photosynthesis. The specific quantity and quality of light we receive directly dictates our ability to produce the sugars that fuel our growth, flowering, and overall vitality. For us begonias, this relationship is particularly nuanced. We are a diverse genus, with species originating from various understory habitats, meaning our light needs are not a one-size-fits-all answer but a spectrum we have adapted to over millennia.
For the vast majority of our cultivated varieties—such as the popular Rex, Rhizomatous, and fibrous-rooted Begonias like ‘Dragon Wing’—the ideal condition is bright, indirect light. This means we thrive in a space that is consistently well-lit, but where the sun's rays never directly touch our foliage. A spot near an east-facing window is often perfect, bathing us in the gentle morning sun. A north-facing window can also be suitable. South or west-facing windows require caution; we appreciate the bright ambient light, but must be shielded by a sheer curtain or placed several feet back from the glass to prevent harm.
When we are subjected to too much intense, direct sunlight, especially during the harsh midday hours, it is a profoundly stressful experience. Our leaves, which are often tender and sometimes richly pigmented, are highly susceptible to scorching. This manifests as crispy, brown patches on the leaf margins or surfaces—a literal sunburn. Beyond the visible damage, the excess light can actually damage our photosynthetic machinery, a condition known as photoinhibition, which paradoxically slows our growth. Furthermore, it causes excessive water loss through transpiration, putting immense strain on our root systems and leading to wilting, even if the soil is moist.
Conversely, a life in deep shade is one of quiet struggle for us. Without adequate light, our photosynthetic rate plummets. We are forced to ration our energy, resulting in several clear distress signals. Our growth becomes spindly and leggy as we stretch desperately towards any available light source. Our stems weaken, and the internodes (the spaces between leaves) become abnormally long. Our vibrant leaf colors will fade and become washed out. Most tellingly, we will likely cease producing flowers altogether, as we lack the energy required for reproduction. A begonia that does not flower is often a begonia pleading for more light.
It is crucial to understand that within our begonia family, some cousins have different tolerances. Tuberous Begonias, for instance, those prized for their magnificent, rose-like blooms, can handle and often prefer a few hours of direct morning sun to promote prolific flowering. However, they still require protection from the intense afternoon sun. On the other end of the spectrum, our heavily hirsute (hairy-leaved) relatives and some deeper-colored Rex hybrids are exceptionally sensitive and thrive in lower light conditions than others. The best approach is to observe our response; we will tell you if we are content through our growth and appearance.
