Last Updated on March 15, 2022 by Admin
One of the most important things when growing houseplants is to understand their lighting requirements.
Different indoor plants have varying light needs. As such, you need to get to know your plant in order to give it proper exposure.
In this article, I will discuss indoor plant light requirements so you know how much light different plants need.
Light is one of the most important factors for your houseplants. That’s because unlike the outdoors or in your garden, there’s a much bigger chance of them not getting enough sunlight.
Most areas in your home don’t get a lot of light from the sun’s rays.
And, those areas that do, may not get direct light. That is, the light they receive has been filtered or is indirect.
More importantly, unlike water, fertilizer and temperature, you can’t always control the amount of indoor light your home receives.
This is why it’s often a good idea to do a little home “recon” before going to the nursery to buy a houseplant. This lets you figure out what kind of sunlight different locations in your home get. With that, you’ll be able to choose the right kinds of plants to get.
Why Do Plants Need Light?
Plants get their energy from photosynthesis.
In simple terms, photosynthesis is the process where plants convert light, water and air (carbon dioxide) into “food”.
By food, I mean that these elements are converted into sugar (glucose). That’s pretty much like what your body does with the food you consume.
But, instead of releasing carbon dioxide like we do when we exhale, plants release oxygen. This is one of the reasons why it’s a good idea to have houseplants indoors. They increase the amount of breathable air (oxygen) for you.
In any case, photosynthesis allows your plants to grow and stay healthy.
But to do so, they need all the aforementioned components.
That’s why light is essential to their growth (and survival).
Thus, it’s crucial that you find a location in your home where your houseplant receives an ample amount of light.
What is Direct and Indirect Sunlight for Plants?
In simple terms,
- Direct sunlight is when the rays of the sun hit your plant.
- Indirect sunlight happens when there’s bright light reaching your plant. But, the sun’s rays aren’t directly hitting it.
The easiest way to imagine this is when you’re standing outside during a sunny day when there are no clouds around.
You experience the full brunt of the sun’s rays. Here, you receive direct sunlight.
In contrast, on a cloudy day, it’s still bright and you can still feel the light. But, you don’t directly get hit by the sun’s rays. This is indirect sunlight.
For your houseplants, direct and indirect sunlight can happen in a few ways.
- How far the plant is from the window. When it’s near the window, it gets direct sunlight. But, if it is 3 feet or more away from the opening, it stills receives bright light. But, not directly from the sun’s rays. As such, it gets indirect sunlight.
- In the morning and afternoons. The sun rises in the east and sets in the west. As such, windows facing east get direct sunlight in the morning. By the afternoon when the sun it on the other side, the window only received indirect sunlight. The opposite is true for windows facing west.
How Much Light Do Houseplants Need?
Just as importantly, not all plants require the same amount of sunlight. In general, they’ll fall under one of these categories.
The good news is, most plants you’ll see in the nursery and stores come with labels. This will tell you among other things how much light that particular plant needs.
Here’s a breakdown of the different categories.
- Full Sun. Plants that are labeled full sun like direct sunlight for long hours daily. This means at least 6 hours a day of light.
- Part/Partial Sun. These plants also love sunlight. But, they prefer less of it. And, not as intense. They do well with 3-6 hours of light a day.
- Part/Partial Shade. Plants labeled part shade prefer some kind of shade. As such, they prefer indirect or filtered (partially blocked) sunlight. While they enjoy 3-6 hours of sun daily as well, they’d prefer getting some protection from the sun’s harshest rays during mid-afternoons.
- Full Shade. These can tolerate low amounts of light. Three hours or less of sunlight daily is enough to keep them growing and healthy.
That said, depending on where you buy your plant and where you live, the labeling may be different. In some cases, it will look more like this.
This one has 3 categories. But, it’s generally similar to the one above. They’re just different in the way they’re stated.
- High/Bright Light. This is direct sunlight. Often it means southern exposure (see below). But, it can also mean light from the east or west depending on the time of day. In either case, this is the most exposure. And, the light isn’t obstructed by objects or other any cover. In general, plants that like high light will need 6-8 hours of full sun a day.
Below is a chart that lists houseplants that need bright light. These need a plenty of light daily whether it is direct or indirect light.
On the right column, I’ve included the scientific name of the plant to avoid confusion since many houseplants have similar common names.
- Medium Light. This is light coming from the east or west sides. It isn’t as bright or intense as the high light or full sun. And, they receive bright light part of the day and indirect light the rest of it. Similarly, plants that like medium light are happy with filtered or partial light conditions.
Below is a chart that lists the indoor plants that like medium light. These don’t need as much light as bright light plants but still need a good amount of it daily.
- Low Light. Plants labeled under this category don’t like a lot of light. In fact, too much light either scorches its leaves or prevents it from growing properly. Here, you want to place them in the windows facing north.
Below is a chart that lists low light houseplants or indoor plants that do well even if low light conditions.
These make them easier to grow in homes that don’t have a lot of natural lighting or window access.
How to Measure How Much Light Your Indoor Plants Get
The toughest thing about natural indoor lighting for plants is that nothing is static. That is, the sun keeps moving throughout the day. And as a result, how much sun your plants get by the end of the day differs from what it got this morning.
This affects the 3 factors mentioned above:
- Intensity. How strong the light or exposure is.
- Duration. How much time or how many hours of sun does our plant get. And, of what intensity at any given time.
- Quality. It is direct or indirect.
These factors are likewise affected by:
- How big your window is
- What side is the window facing
- How far away from the window’s opening did you place your plant
Whew, that’s a lot.
The good news is, all these variables allow you to adjust them in order to get the best results
Unfortunately, I haven’t found a simple way to do this. That’s because the time of day can affect how much sun it gets.
That said, here are two ways I’ve found to be very effective.
The Shadow Test
This is a simple test you can do by observing the shadow cast by your plant.
- Dark, defined shadow means that it’s getting bright, strong/high light.
- Blurry or weak shadow means it’s likely getting medium light.
- Faint shadow that’s blurry or almost not defined means it’s in a low light position.
Sound simple, right?
The problem is that you’ll need to check the shadow every hour or so for an entire day to get a better idea. Doing this will help you figure out whether that location is getting 3, 6 or more hours of sunlight and at what intensity of light.
I highly suggest jotting things on a piece of paper so you can analyze everything at the end of the day.
Using a Light Meter
If you’re into gadgets, you may have a light meter. This is a more accurate way of figuring out how much light your plant gets.
My friend who’s a camera geek also showed me that you can pretty much do this with an SLR camera. Although, there are a few more technicalities involved there since you need to use the right settings.
In any case, a light meter easily does this for you.
A light meter measures the intensity of light in a given location. It does so using foot-candles.
A foot-candle is the unit that’s used to measure light intensity. In general,
- Bright light plants like around 300-foot candles or so
- Medium-light plants prefer 150 to 300-foot candles
- Low light plants are happier with 50 to 100 or so foot candles.
What Direction Should Your Houseplants Face?
One of the things that beginners often overlook is how they position their houseplants.
Often, you’d think that as long as you place your plant by the window, it should get enough sunlight, right?
That’s because the sun moves throughout the day. As such, the amount of sunlight each side of your home actually gets is different.
Add to that the fact that the sun rises and in the east and sets in the west changes how much light each side gets depending on the time of day.
So, what’s a home gardener to do?
Pull out your compass.
If you don’t have a compass, take out your smartphone and click on a compass app. It will show you where’s north, east, west and south, relative to your location.
Why is this important?
That’s because different areas get varying amounts of sunlight. To make it simpler, here’s a quick guide to help you.
North Facing Indoor Plants
Windows facing north receive indirect sunlight. You can likewise call this norther exposure depending on what you prefer.
In general, indirect light isn’t as good direct light. It’s lower in intensity and provides a lower amount of light exposure to your plant.
Most plants aren’t a fan of this condition. It will prevent them from reaching their full potential. For many it will cause them to grow poorly.
The situation also gets worse if you live in a city with four seasons. That’s because the light significantly decreases during the winter months.
As such, you’ll want specific plants that can tolerate low light conditions or prefer indirect light here.
Some examples include the cast iron and snake plants. In case you want to find more options, here are the best low light plants.
If you do decide to grow your houseplants facing north here are a few things that help:
- Place them as near the window as possible for maximum exposure
- Add artificial lighting if your houseplants aren’t getting enough exposure
- Mirrors help in reflecting light
- White surroundings also help the light bounce across the room
South Facing Indoor Plants
For most plants, southern exposure is a very good scenario.
That’s because you get a lot of sun. In fact, of all the four sides, this gets the most exposure.
As such, they’re perfect for plants that like full sun. This includes succulents, citrus, and hibiscus.
The extra sunlight also allows you to adjust things. By this, I mean you’ll be able to reduce the amount of exposure they get. That’s not true for areas that get little light since it’s impossible to boost sunlight manually.
That said, not all plants like tons of sun. At least not for days on end and for long hours.
So, if your plant is getting too much sun, you can:
- Move it farther from the window
- Adjust its position so it doesn’t get complete exposure
- Add blinds or curtains
- Place some objects that will partially block the sun
Doing any of these helps your plants receive bright light that’s filtered. This reduces their intensity.
East Facing Indoor Plants
The window facing east is a great spot for most plants.
It’s perfect for plants that like bright light but aren’t fans of full sun. It also works well for those that prefer moderate to low light conditions.
That’s because the sun rises in the east. As such, they get a lot of bright morning sun. The morning sun is also less harsh than that in the afternoon. So, it reduces the risk of too much intensity.
This makes it also perfect for plants that are prone to sunburn. Or, those that prefer cooler climates.
Depending on where you are and what time of year it is, the amount of sun in the mornings can vary. As such, exposure also varies.
Come afternoon, the sun moves towards the west. As such, the east gets a lot less exposure. But, it still receives ample indirect light. This makes it ideal for plants that enjoy low to moderate lighting.
West Facing Indoor Plants
The west is another compromise to the full sun of the south.
But, it’s hotter than the east side. And, you get more intense sunlight during the afternoons.
As such, it’s a better spot for plants that like warmer temperatures.
And, those that prefer bright indirect light that isn’t susceptible to sunburn.
The reason behind this is that these plants don’t get a lot of bright sun in the mornings. But, come afternoon when the sun is the hottest, they get direct exposure.
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A Few More Houseplant Lighting Tips
Here are a few more extra tips on light and your houseplants.
It’s also worth noting that plants that are known for their flowers are best positioned within a few feet of an open window that receives a lot of sunlight. Some examples include orchids, African violets and gardenias.
16 Hours Maximum
While most plants love sunlight, too much light is counterproductive as well. As a general guideline, don’t exceed 16 hours of light exposure.
This isn’t much of a problem when it comes to the sun since you don’t get much more than 16 hours of sunlight each day. But, when you factor in artificial lighting, that’s when you run the risk of overdoing things.
Rotate Your Plants Regularly
Whichever position you decide to place your plant, you’ll soon realize that one side will likely receive more light than the other. This is less of a problem with artificial lighting since you’re able to strategically position the light source from above.
But, with plants that primarily get their light from the sun, it’s a good idea to rotate your plants once in a while. This allows each side to get an ample amount of light. In doing so, you encourage even growth on all sides.
Think of it like getting a sun tan at the beach. You don’t want to stay in one position too long such that one side of your body is tan and the other one is white.
Too Much or Too Little Light
Like people, your plants will tell you if they’ve had enough or too little of something. The same is true with light exposure.
- Lack of light. This causes your plant’s leaves to shed, turn yellow or not grow. Similarly, lack of exposure also keeps it from flowering as much as it should. Often plants will also tilt towards the direction of the light if they don’t get enough of it. This is called
- Too much light. This will scorch your plants’ leaves (sunburn). In some cases, they also become dull and bleach.
How Do Indoor Plants Survive Without Sunlight?
What happens if you fail the light tests above?
Does that mean you can’t grow an indoor garden?
Luckily, sunlight is not the only way to provide light to your plants. While it’s the best source because it’s natural light, there are alternatives you can turn to.
Here’s where artificial lighting comes in.
Basically, artificial light is just like the lights you turn on at home at night. But, they’re designed to help your plants grow.
That said, like most tools and equipment, you’ll want to understand their specifications before rushing to the store to buy them.
With artificial light, it comes down to three things.
- This refers to how strong the light is. Unlike the sun where you can somewhat gauge its intensity by how bright the rays are, artificial lights don’t work that way. Some bright lights aren’t as intense as lighter ones.
- The sun is the best source of light because it combines the entire color spectrum. You probably remember the mnemonic ROYGBIV (red, orange, yellow, green, blue, indigo and violet). With artificial lights, you’ll need to figure out which ones to get. That’s because these lights can only give you a few of the lights in the color spectrum. Just as importantly, plants at different stages of growth require different colors.
- Red and orange lights help flowering plants bloom
- Blue is perfect for leaves and beautiful foliage
- Red and Blue are important for plant growth
- This is why you’ll see grow lights in different designs and color combinations. Each of these has varying effects on your plants.
- How many hours a day does your plant receive light. In general, artificial light provides lower quality light compared to sunlight. As such, you’ll be able to make up for that by shining the light for longer periods of time. The good news is, grow lights come with timers. So, you don’t need to manually monitor the duration.
Best Types of Artificial Lights for Houseplants
So what kind of grow lights are available?
Here’s a breakdown of the different types. And, a brief explanation of each of them to help you understand them better.
You’re probably familiar with these as you’ve seen them in homes and offices.
Fluorescent lights have white bulbs. They often come in long tubes and produce a slightly bluish light.
These lights are popular with beginners because they’re cheap and require very little installation.
They do well for seeds and can work for plants that are foliage dominant.
One of their biggest advantages is that they don’t produce a lot of heat. So, you can place them near your plants, as close as 5 or 6 inches.
It’s also worth noting that there’s more intensity in the middle and less on the sides. So, do position your plants accordingly.
Incandescent grow lights are another option. But, they’re more ideal for low light plants because they aren’t the most efficient in terms of illumination.
Another option is to use them to supplement locations that are getting some sunlight but not enough for your plants to grow optimally.
These are similar to the bulbs you have a home.
And, if you’ve noticed these bulbs can get hot. In fact, they’re better at getting hot than they are at producing light.
Thus, do keep them at least 18-24 inches away from the plant.
HID (High-Intensity Discharge) Lights
If you want high brightness, HID lights are the way to go. These are much better in terms of quality compared to fluorescent and incandescent grow lights.
They produce their lights by using gases in the center of their tubes. And, different combinations produce different colors.
As you’d expect they cost more as well. Additionally, you can’t just plug them in like you do the other two. HID lights require the installation of special fixtures.
That said, you’ll find two kinds of HID lights: metal halide and high-pressure sodium.
Metal halide lamps emit bluish white light. This makes it ideal for plant that are in their vegetative growth stage.
It’s also worth noting that they lights don’t run as long as high pressure sodium lamps. To give you an example, a 250 watt metal halide lamp will give you about 10,000 to 15,000 hours of light.
High pressure sodium lamps are better if you want to promote flowering. That’s because the light they emit is red orange.
Similarly, they produce more lumens per watt compared to metal halide lamps. This means for the same amount of wattage, these lamps are brighter than their metal halide counterparts.
And, they last longer too. A 250 watt high pressure sodium lamp will give you about 12,000 to 24,000 hours of light.
LED lights use the same technology that you have in your digital devices. And, when used as grow lights they’re able to produce similar results to HID lights.
Larger units can be expensive. But, there are cheaper ones as well. Their biggest advantage over HID lights is that they’re cheap to operate.
LED lights also don’t get hot. So, you can set them up within 12 inches from your plants. Their efficiency and quality beat fluorescent lights as well.
Their downside is that they’re more like spotlights. As such, they’re better for one or a small group of plants.
Below is a summary chart of the different types of artificial lights. It lists down the bulb types, their intensity and where you can use them.