From our perspective as geraniums, the question of sunlight is not one of preference but of fundamental biological necessity. Sunlight is our primary source of energy. Through the intricate process of photosynthesis, we capture photons from the sun and convert them, along with carbon dioxide and water, into chemical energy in the form of sugars. These sugars are the fuel that powers every aspect of our existence: building new stems and leaves, producing our vibrant flowers, developing strong root systems, and defending ourselves against pests and diseases. Without adequate sunlight, this entire system falters. We become weak, leggy as we desperately stretch for a light source, and our ability to produce blooms diminishes significantly. For us, sunlight is synonymous with life itself.
To thrive and express our full genetic potential for lush foliage and prolific blooming, we require a substantial daily dose of direct sunlight. Our ideal scenario is to bask in the warmth and energy of the sun for a minimum of six hours each day. Many of our cultivars will perform even better with a generous eight or more hours of direct exposure. The most beneficial light for us is the strong, yet gentle, morning sun, which provides intense energy without the sometimes harsh, dehydrating intensity of the late afternoon rays. This extended period allows our leaves to maximize their energy production, resulting in robust growth and a continuous display of flower clusters from spring until the first frost.
We are resilient plants and can adapt to conditions with less than ideal sunlight, often referred to as "partial sun" or "partial shade." This typically means we receive between four to six hours of direct sun, often with dappled light for the remainder of the day. In these locations, we will still grow, but our behavior will change. You will likely notice that we produce more leaves and fewer flowers. Our stems may grow slightly longer between leaf nodes as we reach for the light, and the intensity of our flower colors might not be as vivid. While we can survive in such spots, it is not where we will truly flourish and put on our most spectacular show.
Placing us in deep shade, where we receive less than four hours of direct sun, is highly stressful for our systems. Deprived of the energy we need, our growth becomes severely stunted and etiolated—we become spindly and weak, with pale leaves and large gaps between them. Our primary survival instinct in this scenario is to seek light, so we divert all our limited energy into vegetative growth at the expense of reproduction. This means we will produce very few, if any, flowers. Furthermore, a chronically energy-starved geranium is far more susceptible to fungal diseases like powdery mildew and prone to pest infestations, as we lack the resources to mount a proper defense.
While we are sun-worshippers, the intensity of the sun varies greatly by climate. In very hot, southern regions where the afternoon sun is extremely powerful, we can sometimes experience light stress. This may manifest as slight scorching on the edges of our leaves or a general wilt during the peak heat of the day, even if our soil is moist. In these specific climates, we greatly appreciate a location that gives us full, unfiltered sun from morning until early afternoon, followed by light shade or dappled sunlight during the most intense hours. This provides us with the long duration of light we crave while offering a respite from the potentially damaging peak rays.
