All living things need food and water. For plants, light is food. They use it in an important process known as photosynthesis, where the energy of light is captured by chloroplasts, triggering multiple metabolic responses-- one of these being creating sugars (food) for plants. Sugars propel plant growth, so the more light a plant is exposed to, the more energy it will produce and the faster it will grow.
Know these pairs:
These characteristics of light are essential in understanding how and why a plant will behave in your home.
Quality
Quality is based on the color and type of light. Light is energy that comes in varying wavelengths, each with a corresponding color. Colors we can see with our own eyes might not be useful for plants, because they 'see' light differently than we do. Plants appear green because they reflect green light, so green light is worthless to plants. Rather, plants need light they can absorb and utilize like yellow, orange, red, blue and violet, along with invisible light like UV light from the sun and some infrared.
Quantity
Quantity of light is based on the intensity or the brightness of light that reaches the leaves. The more light photons that reach the leaf = the more energy captured and faster growth. Begonias or Oxalis, for instance, depend on powerful light to support their fast-paced growth. Any type of plant that makes flowers or fruits depends on intense light also. These plants are working with basic ingredients like water, CO2, sugars and nutrients that are chemically constructed into complex molecules, like flower pigments, but just when the right light intensity conditions are satisfied. Some plants have self-regulating systems and will even refuse to flower or will try to but fail midway through the process if there isn't adequate intense light.
In and Out
Outdoors, even in the shade, light is bouncing from all angles-- from 360 degrees around and from the 180 degree arc above in the sky. When a plant is inside, light usually only comes from one source, like your sunny window, greatly reducing the angles light is bouncing off from, and the amount of light and essential photons a plant needs. When we bring a plant inside, we actually invoke something called exponential reduction in photon exposure. The poetic quote above helps us remember this fact a little more easily.
Light Bright
You may have heard the terms "bright light" and "low light" plants, but what does that actually mean?
"Bright light" or "full sun" means there is no barrier (curtains or blinds, a tall tree or building that creates shade) between the plant and the source of light (a sunny window). This is where your plant will receive the most bright or direct light while indoors. Ficus, succulents and Monstera are sunlight worshipping plants and should be positioned right in or no more than 2-3 feet from a window. Typically speaking, you would want to place them in the brightest area in the room.
"Medium light" or "filtered sunlight" is light that's been diffused (sheer curtains) between the plant and the light source (a sunny window). Some refer to it as "dappled sunlight". Anything partially blocking the path between your plant and the source of light creates this medium light. Ferns and aroid plants (ZZ and Philodendron) have evolved to survive on the forest floor, so they are used to being shaded from the sunlight. They have not evolved to manage the severe rays of direct sunlight so they prefer medium light conditions.
"Low light" means no direct sunlight will reach your plant. It is probably a few feet away from your light source (sunny window) or any type of area where it can see outdoors but can not see the sky. Low light means less energy and also less food. Some plants can survive in low light environments however they will not flourish.
Keep in mind that the sun changes places in the sky depending on time of day and season, affecting how much light your plant will receive. Track how the light changes throughout the year and change your plants placement accordingly.
