The Science Behind Indoor Plants and Sunlight: How Much Do They Need?
Posted on February 14 2021
The nuances of light requirements for plants can often lead to confusion and frustration, with terms such as direct, indirect, diffused, dabbled, partial, and full sunlight, coupled with the cardinal directions of North, South, East, and West. Even with exhaustive research, it is not uncommon for a plant to reject its home despite its care, leaving its owner frantically searching for answers online and relocating the plant every other day. The paramount importance of light cannot be overstated, for while plants can survive inadequate soil or lack of fertilizer, they cannot exist without light.
Light is an indispensable component for photosynthesis, which creates life-sustaining food for the plant. Chloroplasts within the plant cells capture light energy and trigger a metabolic reaction, resulting in the production of carbohydrates that feed the plant. Plants struggle on a low-carb diet, and this highlights the significance of light for their existence. While plants possess the remarkable ability to acclimate and adjust to fluctuating light conditions, this ability has limits, and a prolonged lack of adequate light could result in stunted growth or even death.
The unique light requirements of each plant vary depending on its species and habitat. For instance, "understory plants," which thrive on the forest floor, require less light than sun-loving succulents. However, even with a thorough understanding of a plant's light needs, it is essential to consider the quality and duration of indoor light. Unlike the outdoors, where sunlight permeates from all angles, indoor light is typically from a single primary source, such as a bright window. The inverse relationship between light and distance implies that plants located just a few feet away from the light source may still experience low-light conditions, lacking the consistent 365-degree light source of the outdoors.
Determining the amount of light that a plant receives can be challenging. However, an easy way to gauge the amount of light that a plant receives is by examining its shadow when the sun is at its brightest. Plants experiencing bright light cast sharp shadows with distinct edges, whereas those exposed to medium or low light have muted and indistinct shadows or none at all.
Low-light plants may survive in dark locations but will not flourish, as they require brighter light to produce food and supply the energy they need to grow. Symptoms of inadequate light include paleness due to insufficient chlorophyll production, legginess with thin and elongated stems, and stunted growth. Conversely, overexposure to light may cause symptoms such as bleaching, sunburn, or yellowing, and plants may also start reaching for the light source. Certain plants, such as Calatheas, may indicate overexposure to light, while others, such as Pilea Peperomias, may not.
To give plants their required light, it is best to make changes gradually and one-at-a-time. As plants take an average of five days to acclimate to new lighting conditions, patience is necessary, and expecting changes overnight is unrealistic.