Houseplants & Light 101: A Guide to Understanding Light for New Plant Parents

My goal in this post is to provide you with a no-nonsense guide to demystify:

  • How the light in your home works for houseplants &
  • Why light is the most important factor when caring for a houseplant.

Table of Contents

Light is the most important resource your plant needs. Here’s why.

All plants need light because light fuels the process (photosynthesis) that creates food for the plant to live and grow.

Photosynthesis uses light energy to convert water and carbon dioxide into glucose (or sugar/food for the plant).

Because light allows the plant to make food to sustain itself and grow, light is essential for a plant to grow and survive.

Why is the amount of light in a home incredibly limited?

Most locations in a home are insufficient to grow plants, unfortunately.

This is because the majority of homes are covered by light-blocking ceilings and roofs, so the only place where sunlight enters a house is through windows, generally on the sides of the house.

Even plants that live on the forest floor beneath a canopy of trees receive light the majority of the day through the spaces between trees’ leaves and branches.

The plants we buy are typically grown in greenhouses before they come to us. Consider the amount of light entering a greenhouse versus a home.

The light, temperature, and humidity are typically very different in a greenhouse versus a home.

Some other factors that decrease the amount of light entering a home:

The glass that windows are made of blocks a decent amount of the sunlight coming in.

If your windows also have a screen, that likely blocks a little more light.

If your windows are dirty, that likely blocks a little more light as well.

If there is a tree or an overhang in front of your window, that blocks even more light.

If there is a tall building close to your window, that might be blocking even more light.

As you can tell, the amount of sunlight entering a home decreases pretty rapidly.

Why do houseplants need to be pretty close to a window to survive?

The reality is that plants are used to receiving more light than our homes offer because they are used to being outdoors.

As a result, they need to be pretty darn close to a window to get the light they need when growing indoors.

Also, take note of anything in front of that window that might be decreasing light levels.

For example, one of my south-facing windows looks out onto our porch. And above that porch is a giant black walnut tree. So, that window (despite being south-facing) really offers low light during summer (when the tree is full of leaves) and offers bright low light in winter (when the tree is bare and blocking less light).

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What is considered Bright Indirect Light (or Medium Light)?

Bright indirect light means that a plant can receive 3-4 hours of direct sunlight with lots of bright, indirect light the rest of the day.

In the northern hemisphere, East-facing and West-facing windows offer bright indirect light.

East-facing windows receive direct sunlight in the morning with indirect light the rest of the day. The morning sun is the most gentle, making it less likely to burn sensitive plants.

West-facing windows receive direct sunlight in the afternoon with indirect light the rest of the day. The afternoon sun is intense and hot, which is great for plants that want a little more intense light.

These window descriptions and orientations are reversed in the southern hemisphere.

IMPORTANT NOTE: Some people will tell you that bright indirect light means that direct sun never touches your plant throughout the day. I don’t believe that’s true.

I have ALL of my bright indirect plants (which is 90% of my collection) in East or West facing windows. They all receive some direct sun and are doing great.

I’ve been fortunate enough to only burn plants under grow lights. Never in windows so far.

If you are located closer to the equator, you may receive more light at a higher intensity throughout the day. As a result, you may need to pull plants a little farther away from the window to prevent burning.

What is considered Full Sun (or High Light)?

Full sun means that the plant wants as much direct sunlight as it can get.

You are looking for the sun to shine in your window from morning until when the sun begins to set for the day.

The only place that offers full sun in the northern hemisphere is in a South-facing window with no obstructions.

Many collectors will move their full sun plants outdoors when the weather allows and keep them indoors only for the times when it is too cold to be out.

I move my cacti and euphorbias outside for the summer because it is the only time I see them grow and thrive. When indoors, they continue to live but don’t really grow. It is just too dark in Michigan, even in summer, to expect much growth out of my cacti if kept indoors year-round.

What is considered Low Light?

Low light means that the plant is likely not receiving any direct sunlight throughout the day.

If a low-light tolerant plant is on the windowsill in a North-facing window (where no direct sun shines in throughout the day), it is still able to receive lots of indirect light and potentially do well.

If the plant is pulled back a few feet from a window offering more light, it is probably receiving low light and might do fine depending on how tolerant it is of low light.

In my experience, most “low light plants” tolerate low light, but don’t actually want that. Even many ferns and other delicate plants can do quite well with more light.

That isn’t to say you can’t grow plenty of plants in a north-facing window. I have successfully grown snake plants, holiday cactus, pothos, and prayer plants in north-facing windows. They did not grow as quickly, but they did grow.

I have a snake plant pulled 4-5 feet back from a west-facing window and it doesn’t grow much because it just isn’t receiving enough light to thrive.

How to interpret how much light your window offers a plant without any tools

Observe how much sunlight shines in that window on a sunny day:

  • No sunshine directly shining in? That is low light
  • Morning sunshine directly shining in? That is gentle bright indirect light
  • Afternoon sunshine directly shining in? That is more intense bright indirect light
  • Sunlight shining directly through the window most of the day? That is high light or full sun (or at least as close to full sun as most of us can get using natural light in our home)

In some ways, observational methods of understanding the light in your house are better than using a compass to determine the direction of the window.

Why? Because the direction of the window doesn’t take into account something that might be blocking it from receiving the full amount of sunlight each day.

If your windows are unobstructed (no trees, buildings, overhangs, etcetera in the way of the light entering your home) and you live in the Northern hemisphere, then you can also use the following guide:

  • North facing windows: Low Light
  • East facing windows: Bright indirect light, gentle in nature
  • West facing windows: Bright indirect light, more intense in nature
  • South facing windows: High light

How do you choose a spot inside that offers bright, indirect light?

Place your plant in front of a window that receives direct sunlight in the morning or the afternoon, but not both.

If your plant has thinner or more sensitive leaves (or if you are worried about sunburn) you could use a sheer curtain or blinds to diffuse some of the light. I don’t think this is necessary for most plants.

If the window you want to use receives direct sun most of the day, pull the plant back a couple of feet so it doesn’t suffer sunburn.

How do you choose a spot inside that offers full sun?

Plants that require full sun really want to be sitting in direct sun all day.

These plants need to be on a windowsill in a window that gets sunlight from morning until sunset.

A good example of a plant that prefers full sun or high light is a cactus.

Cacti have a tendency not to show suffering as quickly as some other plants. But it will become quite apparent over time that a cactus isn’t getting the light it needs when it doesn’t grow at all or grows in a stretched, thin, misshapen way.

When a cactus or full sun plant grows in a stretched, misshapen way, it is desperately searching for more light.

How do you choose a spot inside that offers low light?

Low light is available a couple of feet away from an East or West facing window, directly in a North facing window, or several feet back from a South-facing window.

In other words, most spots in our homes are either low light or no light.

An easy way to know if the spot is low light is to try to read a book in that spot using only natural light. If you can read it easily, it’s probably low light. If you can’t read it easily or feel the desire to turn on a light, it’s definitely not enough light for a plant.

How do you know if your plant likes the spot you chose (i.e. is it receiving too much, too little, or just enough light?)

Your plant is probably receiving enough light if:

  • Your plant is growing
  • Your plant is producing healthy growth
  • Your plant is maintaining healthy coloration

Your plant might want more light if:

  • It isn’t growing
  • It’s majorly stretching toward the light source
  • It isn’t using the water you provide within a week
  • It is growing, but the new growth is weak and lanky

Your plant might want less light if:

  • Your plant’s coloring is beginning to fade/bleach
  • Your plant is using the water you provide too quickly (within a day or two)
  • Your plant is developing white or brown crispy patches from sunburn
  • Your plant is wilting often

All of these symptoms can also be signs of other issues.

For example, a plant that isn’t using the water it has within a week or so could be receiving enough light but might be planted in too large of a pot or in too dense of potting mix.

The only way to know what the issue is is to change or check one aspect of the plant’s care at a time and see if that fixes the issue before making another change.

Big Takeaways

  1. Light is critical for a plant to grow and be happy
  2. The amount of usable light that makes it in our home is pretty small
  3. Most houseplants want at least a little direct sunlight indoors so put your plant in a window that receives some during the day to keep your plant looking and feeling its best

What do you find helpful when thinking about light and houseplants?

Do you like what you read or do you have suggestions for how to improve this post? Let me know if the comments below!

Happy growing, everyone!

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