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A Friendly Lighting Guide for Your Houseplants

What is the first thing that comes to mind when you think of indoor plant care? For many, the main chore they associate with plants is watering. However, it’s by far not the primary factor to consider when buying a new plant or finding a location for your existing houseplants. Lighting is far more significant, as sunlight is a major source of energy for all plant life. Your indoor plants are no exception. 

Therefore, successful houseplant owners always pay close attention to their plants’ light needs, and we’ll teach you to do just that in this brief but informative guide. You’ll learn to read plant labels at gardening centers and develop the skill of noticing the signs of insufficient and excessive light in live plants.

Why do plants need different levels of light?

Lighting Guide for Houseplants plants on your windowsill

Remember the kids in biology class who were always complaining they’d never use photosynthesis in real life? They were wrong, and now is the time to put all that biological knowledge to practical use.

Let’s begin with the obvious. All plants - even carnivorous ones and algae - require light to grow lush and healthy. They have special cells that transform sunlight, carbon dioxide, and water into sugar during the process called photosynthesis. But that’s not all.

Just like other living organisms, plants have evolved over the years to survive in specific climates. Yes, that includes what we call “indoor plants”; after all, all plants came from a natural habitat somewhere, even if that habitat has a very different climate from your own.

Lighting Guide for Houseplants succulent

For example, plants that live in the understory of the forest generally have less light available than those that live in the open. So, these plants often have dark green or even burgundy leaves that catch light more efficiently. Conversely, such plants require limited sunlight to thrive.

On the flip side, desert plants like cacti and succulents have protective features that prevent their leaves from getting scorched in the relentless desert sun. For instance, some succulents are covered by a natural white dusting called epicuticular wax that absorbs sunlight. It’s like a natural sunscreen that repels UV light. Neat, right?

Related article: Increasing Humidity for Your Houseplants

Decoding the categories of plant lighting

The two examples above illustrate that each plant is attuned to a different amount of sunlight. Knowing what climate and living conditions your indoor plants are from can be tremendously helpful. But there’s also a shortcut. 
Lighting Guide for Houseplants plant tag

Decorative plants are typically divided in terms of their lighting needs in stores. The next time you go to a garden center, you’ll surely find a section of low-light plants, and another one with plants that require direct sunlight. Nurseries will also ship out their plants with information tags that list the houseplant’s name, light requirements, water needs, etc.

The only trouble is that these tags use shorthand terms like “bright indirect light” or “low light,” which can be hard to quantify. To give you a deeper understanding of what all these cryptic terms mean, here’s a quick rundown of each category:

  • Direct sunlight: 1,000+ FC

This is the highest light intensity that is usually reserved for desert plants like palms and cacti. To give your plants direct light, you’d place the plant directly on the windowsill of a south- or southwest-facing window. If using artificial light, it equals up to 16 hours of light exposure.

Lighting Guide for Houseplants watering jade plant
  • Bright indirect light: 500-1,000 FC

This is by far the most common plant light recommendation because pretty much any plant you have will love it. In this scenario, your plant is still sitting very close to a window, but it doesn’t receive any direct sun. A synonym for bright indirect light is filtered or diffused light; think of a bright window covered by sheer drapes.

  • Medium light: 250-500 FC

Medium light refers to light areas in your home that don’t get direct sun exposure because they’re around 6 feet (1.8 m) away from a window. From ivy to spider plants, there are a lot of plants that thrive in this type of lighting. And usually, it’s not so difficult to come by in the home.

Lighting Guide for Houseplants fiddle leaf fig
  • Low light: 250 FC or less

Low light is the least amount of light you can give a houseplant without killing it. Not all plants will thrive in low-light conditions, but many will tolerate it. ZZ plants, golden pothos, snake plants, rattlesnake plants, and peace lilies are just a few examples of plants that will treat you kindly, even if you leave them in a relatively dark corner. Small bathroom windows or north-facing windows are more closely aligned with low light.

Also, keep in mind the duration of the light. On average, a houseplant will need 6-8 hours of light every day. In the winter, the sun exposure may drop, and you’ll need to move some of the plants closer to a window.

Lighting Guide for Houseplants calathea ornata
It’s also a good idea to rotate the plant every few weeks – otherwise, all the leaves will move in one direction, and you’ll be left with a lopsided plant.
Lastly, be mindful of dirt and dust - both on the leaves and on your windows. Dirt can further diffuse light and therefore reduce your plant’s ability to photosynthesize, so wipe down the leaves with a damp cloth regularly, and keep the windows clean to help your plants get all the light they need.

How to measure the light in your home

1. Use a light meter

Lighting Guide for Houseplants light meter

Wondering what those numbers next to each lighting category were above? Those are the most common light intensity measurements called foot candles (or FC). One foot-candle is the amount of light emitted from a candle to a 1-square-foot area. Most plants require a light intensity of at least 500-1,000 FC (or at least 15 watts per square foot). You can measure the light intensity in different areas of your home using a specialized light meter. These are available in home goods stores and online. 

Alternatively, you can download an app that uses your phone’s camera to measure light intensity. Apps like Photone for both Android and iPhone, Lux Light Meter Pro for iPhone, and Tent Buddy for Android all do a great job of estimating your lighting conditions.

2. The shadow trick

Lighting Guide for Houseplants plant shadow against a wall
Here’s a less accurate but still reliable way to estimate the lighting situation in your home. Wait for a sunny day, then take a sheet of paper and a plant leaf. Hold the leaf 20 cm (8 in) from the paper at a location you want to test. If the leaf casts a dark shadow with a sharp outline, that location has direct or bright indirect light.
If the leaf outline is still visible but blurry, you have medium light. If the shadow is so diffused that you cannot see the whole outline of the leaf, then you have a low-light area.

3. Window Direction

Lighting Guide for Houseplants plants in the sun
If you’ve been interested in plants for a while, you likely heard someone mention that a specific plant lives best in the Western window. But what does this all mean? The idea behind it is that you can expect different amounts and intensities of light depending on where your windows are facing.
These are the general rules for the northern hemisphere. If you live in the southern hemisphere, just flip them:
  • Southern window - bright indirect to medium light
  • Southwestern window - bright indirect or direct afternoon light
  • Southeastern window - bright indirect light
  • Northern window - medium light
  • Northeastern window - medium or bright indirect light, sometimes direct light in the morning
  • Northwestern window - bright indirect light
  • Eastern window - bright indirect light and direct light in the morning sunlight
  • Western window - bright indirect light and direct light in the afternoon.

Related article: 
What Problems Do Plant Owners Encounter in the Winter?

Does my plant like its current light setup?

Lighting Guide for Houseplants checking leaves of a plant
Telling a thriving plant is easy because it looks healthy and beautiful, with brightly colored leaves and plenty of new growth during the growing season. And if your plant starts blooming, treat it as a compliment to your care and attention. Blooming usually means that you’re doing a great job caring for a plant all around.
Pinpointing an upset plant is not difficult either. The thing that is a bit more challenging is understanding what caused the adverse symptoms in the first place. Begin by ruling out pests, diseases, and other issues. If your plant seems healthy and has received enough water and nutrients, a poor location is all that is left. To identify the underlying cause, watch out for the following signs.
Your plant is not getting sufficient light if:
Lighting Guide for Houseplants sad succulents
1. The new growth is leggy or spindly. This is especially visible in rosette-shaped succulents that elongate their stems and may lose their rosettes completely in low light.
2. The plant is leaning toward the window or another light source.
3. The plant is dropping its leaves.
4. The leaves look pale, and the new growth is much smaller. 
5. Variegated species revert to their solid green hue.
6. No new growth.
The solution to this issue is simple – just move the upset houseplant to a brighter location. If you don’t have any free space, you can always supplement the light with specialized grow lights or at least a regular LED. Just make sure to place the light rather close to the plant.

Your plant is receiving excessive sun if:

Lighting Guide for Houseplants burnt palm tree
1. Scorching - dark or brown spots on the leaves.
2. Crispy edges on the leaves.
3. Discoloration - dry and white areas on the leaves.
4. The soil dries up too quickly compared to your other plants.
5. Wilted leaves.
Unfortunately, the scorched leaves cannot be saved, but if you act fast, you’ll be able to save the entire plant from the excessive sun and heat. Obviously, you need to reduce sun exposure. This can be done by moving the plant to a less sunny location or hanging a sheer screen or curtain over the plant. This will filter out some of the light. Just don’t put the plant in the darkest corner, and avoid overwatering it right away; the shock may kill the plant.
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