All About Light

Houseplants absorb light and emit joy into every space they enter. Lush greenery and striking variegation bring together a cozy, inviting space. To ensure your plants receive the light they require, you must understand how plants interpret and process light levels. To maximize the joy for us, we must maximize the light for them.

Why do plants need light?

Light is one of the most important factors in plant growth as it provides the energy source for photosynthesis. Photosynthesis is the process by which plants convert light energy into chemical energy, utilizing water, and carbon dioxide to produce chemical energy sources, namely glucose, which can later be broken down through the process of cellular respiration to fuel plant growth processes. Light is received through specialized plant structures (organelles) called chloroplasts. Chloroplasts contain a specialized light-absorbing pigment called chlorophyll, which also gives plant their signature green appearance. Chlorophyll absorbs energy from the blue, red, and far-red areas of the light spectrum and reflects green wavelengths, making plants appear green. This is also why many LED grow lights have red, blue, or purple light streams.

How do plants receive light in the home?

Whether you have plants huddled in every window, an extensive configuration of grow lights, or one plant plopped on your desk, you are at least somewhat aware of how much light your plants receive. But how much is enough? General lighting recommendations can often be frustratingly vague or extensively complicated.

The simplest way to understand how your plant is receiving light is to envision quite literally what your plant is seeing when sitting on your windowsill or shelf. Does your plant see the open sky or a large oak tree? Does your plant ever see the sun directly, or just the sky? Light requirements in the home can broadly be thought of as your plant’s proximity to the light source or window, as well as what the plant sees (sun, no sun, etc.).

Light levels drop off considerably with distance from your window or grow light. It is best to place plants as close to a window as possible, keeping in mind cool winter drafts or blazing hot sun that may negatively impact growth. Any distance outside of three to four feet from your window should be thought of as low light conditions.

When placing plants right near windows, what amount of light is your plant getting, and what does “bright, indirect light” mean anyway? Window lighting can be thought of in two parts:

1. What cardinal direction is the window facing?
2. What does the plant see?

For cardinal directions in the northern hemisphere, generally:

• North: No direct sun; best suited for low- to medium-light plants.
• South: Reliable bright, direct sun; best suited for direct sun plants, medium- to bright indirect light plants.
• East: Gentle, direct sun in the morning with bright, indirect light in the early afternoon; best suited for low- to medium-light plants, as well as bright, indirect light plants if the window is quite large.
• West: Low or indirect light in the morning, and hot, bright and direct sun in the afternoon; best suited for medium- to bright, indirect light plants and suitable for direct sun plants depending on conditions.

After considering the general direction your window is facing, it is then time to be the plant, envisioning what your plant sees each day. Take any outdoor obstructions such as shade from trees or shadows from buildings into consideration, as well as where you set the plant in relation to your window.

Generally speaking:

• Direct sun is a direct view of the sun in the sky. Your plant is receiving direct sun if at any point in the day it has an unobstructed view of the sun. This is ideal for sun-loving plants such as cacti and succulents but may also be okay for some bright, indirect light plants depending on how long they are exposed directly to the sun. A couple of hours of direct sun is usually no big deal at this northern latitude.
• Bright, indirect light, the buzzword of the houseplant world, is a great lighting situation for most plants. Bright, indirect light means that a plant has a clear view of the sky but does not necessarily see the sun itself. This could mean that a plant is off to the side of a window and sees light and the sky at more of an angle. This is ideal for almost all plants, apart those requiring direct sun.
• Medium light describes either a clear view of the sky with no direct sun, perhaps in a north window receiving less intense light, a small distance from a window receiving bright, indirect light, or a few feet from a window receiving direct sun.
• Low light describes any situation outside of those described above, including any distance outside of about three to four feet from a window or in a shaded window, among other situations. Many houseplants can tolerate these conditions, including ZZ, Snake Plants and Pothos, although these plants will also accept brighter light if it is available

How do I know if my plant is receiving enough light?

If your plants are upset with their light situation, they have many ways to communicate their discomfort. Here’s what to look for when assessing if your plant’s needs are met.

Signs your plant is receiving too little sun:

• Pale green or yellow coloration
• Stretched, leggy growth that appears to be growing toward the light
• Soft growth that does not harden off
• New growth that blackens quickly
• Soil that stays too wet for too long
• Leaf drop
• Reversion of variegation back to green

Signs your plant is receiving too much sun:

• Bleached white coloration
• Copper or sun burned splotches
• Brown, crispy leaves or spots
• Leaves curling inward

Follow these enlightening tips to ensure your plants grow happy and healthy in your space! For a more exacting and measurable approach, check out our All About Light Meters Blog and our All About Light Meters Video!