An Easy Chart & Explanation to Determine Your Plant's Lighting Requirements
Posted on March 21 2021
We’ve all been there: there’s a specific place in your home you want to fill with a houseplant. You purchase the “perfect” specimen, place it in its new home, only to relocate it a few weeks later because it is withering away. You buy another plant, and the same thing happens. How can you determine how much light a plant needs? And how does that translate into your home environment? Check out the easy explanation and chart about how to fulfill your plant’s light requirements!
The Importance of Light
Natural light plays a vital role in the life of your plant. [Link to the Science Behind Indoor Plants and Sunlight] They need it to produce pigment (chlorophyll) and for energy (through photosynthesis). Not enough light? You will end up with a weak, pale plant that is also likely overwatered because the roots aren’t growing enough to absorb moisture. It’s a pretty sad situation, no?
The Challenges of Window Placement
If you are a directionally challenged plant parent, don’t despair. While understanding which direction your window is facing can be helpful, it’s not a fail-proof way to determine how much light your plant is receiving.
For example, what if a tree or building obstructs your brightest south-facing window? How can you determine the amount of light that is really hitting your plants? What if you have small windows? Or sheer curtains so you can hide from your neighbors?
The Shadow Test & Plant Light Chart
That’s where “The Shadow Test” comes in: it helps you determine the amount of light your plant is receiving in your environment.
- Prepare yourself by getting a large, blank piece of paper.
- At the brightest part of the day, place your paper vertically, facing the light source, at the height and location you would like your plant.
- Put your hand a few inches away from the paper.
- Use the Light Requirement Chart to figure out what type of lighting your plant will be receiving.
An area that has Low Light will have a faint shadow, with little to no definition. What does this look like? You should not see your fingers, but you should see some type of shadow. Most likely, it will be an indistinct blob.
As you can see on the Light Requirements Chart, your plant is probably near a North-facing window. This location will never receive any direct sun and is only suited to Low Light Plants, such as the Sansevieria, ZZ, and Parlor Palms.
Is there no shadow? No shadow indicates that this location is not suitable to plant life. Are you looking for a loophole? Many Low Light Plants can survive for a time in no-shadow conditions. However, they will not grow. If you are determined to fill this spot, you have a few options:
- The Tag-Team: Rotate two low-light plants. Place one in a brighter location (bright indirect lighting would be most suitable for this method) and the other in the darker area. After two-to-three weeks, swap them out.
- The Summer Vacation: Many Low Light Plants will overwinter in shadier locations because they are not actively growing. During the growing season, relocate them to a brighter space or outdoors. During dormancy, place them in this no-shadow location.
- The Winter Vacation: There are a few plants out there that require more light during the winter months and lower lighting conditions in the summer. The Christmas and Thanksgiving Cactus require lower levels of light until a few months before blooming.
Keep in mind; you should never place your Low Light plant in a room without any windows. Only use the above methods in a room that receives some natural light.
An area that has Bright Indirect Light will have a weak shadow with a silhouette. What does this look like? You may have to move your hand and wiggle your fingers to find your shadow, but you should be able to see your fingers once you do.
According to our Light Requirements Chart, this can mean your plant is near a South facing Window or an East/West Facing Window. How can you tell the difference?
- South-facing windows will receive full, direct sun for the whole afternoon.
- West-facing windows receive full, direct sun in the late afternoon and evening.
- East-facing windows receive some full, direct sun in the morning hours.
Distance Makes a Difference
Plants labeled for Bright Indirect Light are not well suited for direct sun, especially in the afternoon hours. Place your plant away from the sun’s rays: 3-5 feet away from a South facing window or 5 feet away from one that faces West/East.
Don’t forget to do the shadow test: try out your new location before moving your plant. If you see a distinct shadow, move your plant a few more feet away from the window.
An area that has Bright Direct Light will have a well-defined shadow. What does this look like? You will see a very dark, high-contrast, sharp shadow detailing all of your fingers.
“Bright Direct” is the easiest type of light to determine because you can see the light on your floor or wall.
Looking at the Light Requirements Chart, that shows that your plant is nearby a South facing window. Why? At the brightest part of the day, the South-facing window is the only one receiving direct sun. These windows have the longest, harshest duration of direct light. Only place suitable plants close to these windows, as it will sunburn plants with other light requirements.