There are a lot of words to describe light in the houseplant world: low, medium, bright, direct, indirect, filtered etc. It can be really confusing when you’re shopping and see these on a label without knowing what they mean. Not knowing for sure whether there’s enough light in your space for a certain plant is a gamble that can shorten its lifespan. Worry not - once you reach the end of this post, you’ll know a lot more about the light in your home and will be much better equipped for your next stop at the greenhouse.
Before we get into definitions, there are a couple of critical things to know about the sunlight your home gets. Think of a spot where you’d like to put a plant and keep it in mind while you read on.
First, I want you to think about what direction the windows nearest that spot are facing. Because of how the Earth spins on its tilted axis, the brightest direction will depend on where you are on it.
I live in Missouri, so that will be the reference point for the rest of this post. These guidelines should apply if you’re on the same side of the equator. If you’re on the opposite, switch the guidelines for north and south. Unless you’re a flat earther. Then I can’t help you.
Here, we’re relatively far north of the hemisphere, so the Sun stays in the southern half of the sky for all but maybe a few weeks of the year. This means that south facing windows will consistently receive the most sunlight throughout the year compared to other directions. Sunlight in the evening is a bit more intense than in the morning, so west facing windows are the next brightest, followed by east, and lastly, north. North facing windows will maybe get some direct sunlight during the summer, but for the rest of the year, consider the north a low light direction.
Next I want you to note how exposed those windows are to the sky. Are they able to soak in the sun all day? Or are you in a shady area with buildings or trees that might be blocking them at different times? The longer the window is exposed to sunlight, the “brighter” of a spot you can consider it.
Now that we know these things about the spot you’ve been thinking of, let’s get into what some of these terms mean.
Filtered Sun vs. Full Sun
-
All light that comes through a window or other barrier is considered filtered.
-
When the sunlight touches your plant outdoors without passing through any barrier, it’s getting full sun.
Direct vs. Indirect
-
If your plant can see the sun, it’s getting direct sunlight.
-
Picture a spot right up in a window that sees the sun for most of the day.
-
South will get the most consistent direct sun, west gets some for a few hours in the evening, east facing windows will get that mild morning sun, and north windows will get none but for a few weeks during the summertime.
-
If your plant can’t see the sun, it’s getting indirect sunlight.
-
This will be a spot directly next to or a bit away from a window that gets sunlight.
-
Note: If a plant prefers indirect light, it doesn’t mean that it can never be exposed to direct light without adverse effects. Some plants leaves will burn after too long in direct sun, but typically they can handle some for a short amount of time.
Bright, Direct Light
-
This is right up in a window that faces a direction that gets sunlight for a solid chunk of the day.
-
The amount of time this spot gets direct sun matters. Plants that need bright, direct light want to see the sun for the majority of the time it’s in the sky.
-
-
Remember this key point throughout the rest of this post: The direction your windows are facing matters. From the perspective of the Midwest US, the brightest to dimmest directions are south, west, east, north.
-
North is not a great option for plants that love bright, direct light. If you only have north facing windows, fear not and see my post on tips for low light homes.
Bright, Indirect Light
-
This means that the plant is not in a spot where it can see the sun, but it gets a lot of ambient light from being close to an area that does.
-
Think to the left, right, or maybe 5ish feet away from a window that gets direct sun.
-
Some direct light will be ok for plants that prefer indirect light. Whether it will adversely effect the plant or not will depend on the amount of time it spends in that direct light. The less the better for this category.
Medium Light
-
This is mostly indirect light, around 5-10 feet or so from a window that gets sun for a good part of the day.
-
If any, plants in a medium light spot will get direct sun for maybe an hour.
-
I’d consider right up in a north facing window to generally be a medium light location.
Low Light
-
The farther away from the light source you get, the lower the light should be considered.
-
Some examples of low light spots:
-
Across the room from windows
-
Rooms or areas with only north facing windows, especially during winter months
-
Behind anything obstructing most of the light source, like furniture, other plants or on a bottom shelf
-
If all your spots are rated as low light, you can find a list of low light loving plants and things you can do to help them out over on my aforementioned post, Low Light, No Problem.
If you want to get technical, light intensity is measured in units of lux. You can use free apps like Light Meter to take a photo from the perspective of where you’d like to measure, and it will tell you how many lux that spot received at that time. Remember that this will change throughout the day, so you may want to measure at a few different times to see how long that spot is receiving how many lux.
After reviewing a few resources, the definitions fall somewhere along these lines:
-
Low light - 300-2,000 lux
-
Medium light - 2,000-10,000 lux
-
Bright, indirect light - 10,000-20,000 lux
-
Bright, direct light - 20,000-50,000 lux
-
Full sun (outdoors) - 50,000+ lux
Knowing what kind of light your home gets is critical to your houseplant’s survival. It guides what plants will do well in your space and whether they’ll thrive in certain spots vs. others. Take a walk around your home and start noting which spots get which kind of light. That will help you navigate your next stop at the greenhouse like a pro.
If you have any questions or need further guidance, Slow Green Death is here for you. Send a message on the Services page for more information about how we can help.
May all your plants’ deaths be Slow and Green,
Lindsey
Original post date: March 26, 2023