Bright Indirect Light Explained

Bright Indirect Light Explained

I used to think “bright indirect light” was just fancy plant-person code for “somewhere near a window.” Then I killed a gorgeous Philodendron micans by putting it in what I thought was the perfect spot, only to watch its leaves turn crispy and brown within a week. Turns out, that sunny corner was getting direct afternoon sun, and my poor plant basically got cooked.

If you have ever stood in a plant shop, read a care tag that said “bright indirect light,” and thought “what does that even mean,” you are not alone. I have been there. I still get confused sometimes. But after years of trial and error (and a few plant funerals), I have figured out what this phrase actually means in real life, and I want to share what I have learned with you.

What does ‘Low Light’ really mean?

Before we talk about bright indirect light, we need to talk about what it is not. A lot of people think “low light” means a dark corner or a room with no windows. It does not. Most houseplants cannot actually survive in true darkness or near darkness. When plant care guides say “low light,” they usually mean a spot that gets some natural light, but not much.

I learned this the hard way with a Snake Plant. Everyone said they could survive anywhere, so I stuck mine in my hallway with zero windows. It did not die immediately, but it stopped growing completely and the leaves started looking dull. When I moved it to a room with an east-facing window (but across the room, not right next to it), it perked up within a few weeks.

According to research from the University of Georgia Extension, low light conditions for houseplants typically mean areas that receive between 50 and 150 foot-candles of light. To put that in perspective, that is roughly the amount of light you get a few feet away from a north-facing window or in a room with windows but where you are standing several feet back from them.

The tricky part is that “low light” does not mean the same thing to every plant. A Pothos might tolerate it and keep growing (slowly), but a Fiddle Leaf Fig will throw a tantrum and drop leaves. Most plants that come from tropical forest floors, where they grow under a canopy of trees, can handle lower light. But they still need some light to survive.

Here is what I have noticed in my own apartment: low light spots are places where I need to turn on a lamp during the day to read comfortably. If I can read a book by natural light alone without straining my eyes, that is usually not low light anymore.

North vs. South facing windows

This is where things get practical. The direction your window faces makes a huge difference in how much light your plants get, and this is something I wish someone had explained to me when I first started.

In the Northern Hemisphere (where I live), south-facing windows get the most intense light throughout the day. The sun is in the southern sky, so these windows get direct sunlight for most of the day, especially in winter when the sun sits lower on the horizon. I have a south-facing window in my bedroom, and in the summer, that spot gets absolutely blasted with light from about 10am to 4pm. I can only keep sun-loving plants like my Jade or Cacti right in that window.

North-facing windows are the opposite. They get the least direct sun, usually none at all. The light that comes through is softer and more consistent throughout the day. This is actually my favorite window type for a lot of my plants. My north-facing kitchen window is where I keep my Calatheas and my Nerve Plant, and they love it there. The light is gentle and steady.

East-facing windows get direct morning sun, which is usually softer and less intense than afternoon sun. I have one in my living room, and it is perfect for plants that like bright light but can get scorched by too much intensity. Morning sun is cooler and less likely to burn leaves. My Monstera sits about three feet from this window and has been growing like crazy.

West-facing windows get direct afternoon sun, which is the most intense. If you have ever stood near a west-facing window on a summer afternoon, you know it can feel like an oven. According to Iowa State University Extension research, west-facing windows can be challenging for many houseplants because that afternoon sun is so strong. I learned this with my Philodendron. That afternoon sun was just too much.

The thing is, you can adjust for your window direction. If you have a super sunny south or west window, you can move plants back from the window or use a sheer curtain to filter the light. If you have a north window, you can put plants right up close to maximize what light they get.

Above: A close up look at the symptoms.

Signs of sunburn

I wish plants came with little alarms that went off when they were getting too much sun, but instead, they just show you through their leaves. Learning to read these signs has saved me from losing more plants.

Sunburned leaves usually show up as brown, crispy patches. Sometimes they look bleached or faded, almost like someone took a lighter to them. On my Pothos, sunburn showed up as pale, papery brown spots on the leaves that were facing the window. The leaves on the other side of the plant, the ones facing away from the window, were fine.

One thing that confused me at first was that sunburn can happen fast. I moved a String of Hearts to a sunnier spot one morning, and by that evening, some of the leaves had already started showing signs of damage. It does not always take weeks. If the light is intense enough and the plant is not used to it, damage can happen in hours.

Different plants show sunburn differently. My Alocasia got these weird yellow patches between the leaf veins before they turned brown. My Rubber Plant got dark brown spots that almost looked like a disease at first. According to the University of Maryland Extension, the key is to look at where the damage is happening. If it is only on the side of the plant facing the brightest light, or only on the top leaves that are getting the most exposure, it is probably sun damage.

Once leaves are sunburned, they do not recover. I used to think if I moved the plant to a better spot, the damaged leaves would heal, but they do not. You can trim them off if they bother you, or just leave them. The important thing is to move the plant before more leaves get damaged.

Signs of low light (Etiolation)

On the flip side, too little light causes its own set of problems. The fancy word for this is etiolation, and once you know what to look for, it is pretty obvious.

Etiolated plants get leggy. They stretch toward whatever light source they can find, and in doing so, they grow long stems with lots of space between the leaves. I had a Tradescantia that was beautiful and full when I bought it, but after a few months in a dimmer corner, it started growing these long, spindly stems with tiny leaves spaced far apart. It looked sad and sparse.

The leaves on a light-starved plant also tend to be smaller and paler than they should be. My Monstera puts out huge, deeply split leaves when it is happy in its bright spot near the east window. But when I had it in a darker corner, the new leaves came in small and barely split at all. The plant was basically conserving energy because it did not have enough light to support big, fancy leaves.

Another sign is that the plant just stops growing. I had a Philodendron Brasil that sat in the same spot for six months without putting out a single new leaf. When I moved it closer to a window, it started growing again within weeks. Plants need light for photosynthesis, and without enough of it, they go into survival mode.

According to North Carolina State University Extension research, etiolation is your plant literally searching for light. In nature, a plant growing under dense canopy will stretch upward trying to reach a gap in the trees where it can get more sun. In your house, it is doing the same thing, but there is no gap to reach.

The good news is that etiolation is usually easier to fix than sunburn. Move the plant to a brighter spot (gradually, so you do not shock it), and new growth should come in healthier and fuller. The leggy parts will stay leggy, but you can prune them back to encourage bushier growth.

Above: The tools you need to fix this.

Measuring light with apps

For a long time, I relied on guesswork and plant reactions to figure out if my light was right. But then I discovered light meter apps, and honestly, they changed everything for me.

I use a free app called Photone (there are others like Korona Lux Meter too). You just open the app and point your phone camera at the spot where your plant is. It gives you a reading in either lux or foot-candles, which are units of light measurement. I know it sounds technical, but stick with me because this is actually really useful.

Here is what I have learned from using these apps: bright indirect light usually falls somewhere between 400 and 800 foot-candles (or about 4,300 to 8,600 lux). That is the sweet spot for most common houseplants like Pothos, Philodendrons, and Monsteras. Low light is usually under 200 foot-candles, and anything over 1,000 foot-candles might be getting into direct sun territory, depending on the plant.

The first time I measured the light in my apartment, I was shocked. That corner I thought was bright because it felt sunny? It was only getting about 150 foot-candles. My north window that I thought was too dim? It was actually getting a solid 500 foot-candles in the middle of the day. My perception of light was way off.

One important thing to know is that light levels change throughout the day and throughout the year. I measure my spots at different times (morning, midday, late afternoon) to get a sense of the range. And I measure again when the seasons change, because that south window that gets 800 foot-candles in winter might get 1,500 in summer when the sun is higher and stronger.

These apps are not perfect. They are not as accurate as professional light meters, but according to research published in HortTechnology journal, smartphone light meter apps can be reasonably accurate for general plant care purposes. They give you a ballpark figure, which is way better than guessing.

If you do not want to use an app, there is an old trick I learned from my mom: the shadow test. Hold your hand about a foot above where your plant sits at midday. If your hand casts a sharp, well-defined shadow, you have bright light. If the shadow is soft and fuzzy, you have moderate light. If there is barely a shadow at all, you are in low light. It is not scientific, but it works.

At the end of the day, understanding light is probably the single most important thing for keeping houseplants alive. It is more important than watering schedules or fertilizer or humidity. Get the light right, and most other things fall into place. Get it wrong, and nothing else you do will really matter.

I still mess up sometimes. I still put a plant somewhere and realize a few weeks later that the light is not right. But now I know what to look for, and I know how to fix it. And honestly, that is half the battle.

References

University of Georgia Extension. (n.d.). Growing Indoor Plants with Success. College of Agricultural and Environmental Sciences.

Iowa State University Extension and Outreach. (n.d.). Light and Houseplants. Department of Horticulture.

University of Maryland Extension. (n.d.). Houseplant Diseases and Disorders. Home and Garden Information Center.

North Carolina State University Extension. (n.d.). Interior Plants: Selection and Care. Department of Horticultural Science.

HortTechnology. (2020). “Accuracy of Smartphone Applications for Light Intensity Measurements.” American Society for Horticultural Science, 30(3), 295-297.