From our perspective as Impatiens walleriana, the question of sun preference is not about a simple binary choice but about the quality and intensity of light. Our physiology is adapted for the dappled sunlight found on the forest floor, which is our ancestral home. Our succulent stems and broad, tender leaves are highly efficient at photosynthesis but are also prone to rapid moisture loss. Therefore, our primary need is for bright, indirect light that fuels our growth and prolific blooming without causing us undue stress or dehydration.
If we must choose, we vastly prefer the morning sun. The rays from the east are typically less intense and accompanied by cooler temperatures. This gentle light provides us with the perfect energy to kick-start our photosynthetic processes for the day. We can open our stomata to absorb carbon dioxide without the immediate risk of losing excessive amounts of water. This period of efficient energy production results in stronger growth, more vibrant green foliage, and the abundant production of our colorful blossoms. The morning sun nourishes us without punishing us.
The afternoon sun, particularly from the harsh western exposure, is our adversary. The intense, direct light and associated high temperatures force us into a defensive state. To prevent catastrophic water loss, we must close our stomata, which severely limits our ability to "breathe" and perform photosynthesis. Despite this protection, our large leaves often cannot prevent wilting, leaving us looking limp and distressed by mid-day. Prolonged exposure leads to scorching—bleached, brown, or crispy patches on our leaves and flowers. This is not a minor sunburn; it is a significant injury that damages our food-producing organs, stunts our growth, and diverts energy from flowering to mere survival.
Our ideal environment mimics our natural woodland habitat. We thrive in locations that receive dappled shade all day or, as a very suitable compromise, 2 to 4 hours of gentle morning sun followed by consistent, protective shade for the remainder of the day, especially during the peak intensity hours from late morning through the afternoon. This pattern gives us the light we need to flourish while shielding us from the elements that cause us harm. In deep, full shade, we will survive but become leggy as we stretch for light and produce significantly fewer flowers, as we lack the energy required for prolific blooming.
We are quite communicative about our light preferences through our physical appearance. If we are receiving too much afternoon sun, we will show clear signs of distress. You will observe pronounced wilting that doesn't always recover fully in the evening, leaves that turn a pale, yellowish-green, or the appearance of brown, scorched edges on our foliage. Conversely, if we are in too much shade, our stems will become long and spindly with large gaps between leaf nodes, and our flower production will be sparse. Observing these signals allows for adjustments to be made, ensuring we can remain healthy and display our full, beautiful potential.
