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How To Tell What Kind of Light You Have for your Houseplants

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Indoor plants need light, and you might be inclined to think, “the more light, the better,” but that’s not necessarily true. Different plants have different light requirements, and like other things, there is such a thing as too much light for some plants. 

If you’re considering indoor plants on a spectrum of the light they need, on the low-light end of the spectrum, you’d have something like a ZZ plant that can survive with no direct light or even in fully artificial light. Comparatively, in the full bright direct sun every day for hours on end, you have cacti. All the other indoor plants fall in between those on the light requirements spectrum. 

But, knowing if you can meet the indoor light requirements for your houseplants can be a bit challenging. So how do you tell what sort of light you have in different rooms of your home? 

Well, there are two main ways: estimate based on general guidelines (that’s what we’ll show you how to do in this post), or you could get technical, buy a light meter, and start tracking and measuring the light levels at different times of day in different areas of your home. 

If you’re a tech or data lover, then that might be right up your alley, and we say, all the power to you. But, for the rest of us, here are some general guidelines on how to estimate if you have the correct light requirements for all your favorite indoor plants.

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Mapping the Light in Your Home 

There are three things to keep in mind when you’re thinking about how much light your plants get during the day:

  • Light duration: the number of hours of light a plant receives in a day. 
  • Light intensity: how bright the light is that your indoor plants get.
  • Season: the angle of the sun in your windows changes throughout the year.

Light duration, light intensity, and the season will factor into deciding where you should place different plants in your home based on their light requirements. Throughout the year, the angle of the sun in your windows changes. In winter, most north-facing windows don’t get any sun at all. But at our latitude, in Iowa, in mid-summer, most north windows will get some late afternoon and evening sun. They won’t get much, and the intensity will be pretty low, but there will be some. 

Indoor plants are usually categorized as having low-light, medium light, or bright light requirements. 

  • Low light: somewhere that receives no direct sunlight, for example, near most north-facing windows in winter
  • Medium-light:  windows that receive some natural light during the morning or evening, so east or west-facing windows, and some north windows in summer
  • Bright light: is very brightly lit areas, south or southwest windows that receive full sun for several hours per day

Most indoor plants need about 12 hours of their preferred type of light per day.

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How to Create a Lightmap

You can estimate how much light is in each room of your home by just starting to pay attention to where the shadows are during the day. As you begin to look for shadows and notice the intensity of the light during the day, you’ll start to see patterns and get an idea of what areas of your home are best for your plants bright light, medium light, and low-light requirements. 

There is another way you can measure it a little more precisely without buying a light meter. You can create a lightmap for the rooms in your house, just like you could for your yard. To make a lightmap of your home, you’ll need four copies of your house’s layout and a pencil. If you want a detailed map, you can do this in each season. If you want a more basic idea, you can just do it once during midsummer. Doing it on each equinox and each solstice would give you a good guideline for the year, but you don’t have to do it on the exact solstice. 

In summer, set yourself alarms for 7 am, noon, and 7 pm to create your lightmap. In the winter, start about an hour after sunrise, and do the last one about an hour or two before sunset. At those times, sketch where the shadows are in each room of your house on a fresh copy of your floor plan, and write the time of day on it. 

It’s generally best to do your lightmapping on a sunny day so you can see clearly defined shadows, but if your day starts sunny and then gets cloudy, don’t worry too much; you can complete it on another sunny day. 

When you have your maps done, take your last clean copy, and then layout your 3 completed maps and compare them. 

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Color-Coding Your Lightmap

On your last map, color the areas of each room that got no direct light at all during the day in dark gray. Then, color in areas in each room that got direct sunlight for only part of the day as light gray. Now, what’s left uncolored should match the areas of each room that got direct light for most of the day, and you have a completed lightmap for your home. 

In general, you can consider the areas that are white or uncolored areas as bright light, the light gray areas medium-light, and the dark gray areas low light. 

If you do decide to do this for each season of the year, you’ll probably want to stick with four different final maps, or your color-coding could get complex and challenging to understand. 

Just having this map done for midsummer will still give you good guidelines for the rest of the year. As the sun changes, you can check a room at mid-day and compare where the shadows are at that moment to your summer lightmap. If you had medium light requirement indoor plants across the room from a south-facing window in the summer, they might be getting lots of direct light during the winter, so you may want to relocate them for a few months. 

Last but not least, light intensity depends on the weather in Central Iowa. Bright sunny days will obviously have lots of bright light, overcast days will turn bright light areas into medium light areas, and really dark stormy days will turn every area into a low-light area. 

And there you have it, your very own personal color-coded lightmap for your household. This should make it easier to decide where to put your houseplants, so they are able to thrive throughout every season of the year. Happy mapping! 


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