Direct vs Indirect Sunlight

Last Updated on February 7, 2022 by Grow with Bovees

When it comes to the cultivation of plants, whether they are indoor or outdoor plants, one of the biggest aspects of plant care is light.

Some plants prefer to receive direct sunlight, whereas others thrive better in natural light that is indirect, and then you also have those plants that enjoy a bit of both.

But, when it comes to lighting for plants, what is the difference between direct sunlight and indirect sunlight?

The light that comes through a window can also be measured as direct or indirect. The light differs depending on the direction that the window is facing.

In this article, we will provide you with some information on the differences between direct and indirect sunlight and how you can easily provide your collection of plants with the best lighting conditions for them by identifying the perfect spots in your house.

The Difference Between Direct and Indirect Light For Plants

Just as the color of light affects plant growth, the proper amount of light is also a very important aspect of growing a vibrant and healthy plant. Although the lighting requirements of types of plants differ, most varieties of houseplants thrive best in indirect lighting.

There are some indoor plant varieties, however, that tolerate direct light. These include cacti, snake plants, croton and succulents — just to name a few.

Finding the right light for your greens has a lot to do with direction, but before we get into that, let us define what direct and indirect light is.

Direct Sunlight

Direct sunlight is quite a straightforward term to explain. It is exactly what the words say it is.

This is when a shrub gets direct light, without anything obstructing or blocking the sunlight it receives.

There are a few things that can be in the way of sunlight, blocking it from reaching the plant directly. You may not think of all the obstructions, but if you observe you will find some. These could be houses, trees or their branches or other objects that are higher than the plant itself.

So, we could say that light without obstruction is the key part in this case. Keep in mind that direct sunlight shining through a window is weaker than direct sunlight shining on plants outside.

Indirect Sunlight

If a plant is given indirect light, it means that it is placed in an area that is bright, but the rays of the sun are not in direct contact with the foliage.

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This could be light that is shining on plants through a sheer curtain, for example. Placing your shrub in a bright but shaded area is also considered to be an area where it can receive indirect sunlight.

Direction

Now that we know the key differences between direct and indirect light, let us talk about the importance of direction.

By placing your plant into the correct facing window, you can control how much light — whether it be direct or indirect — it can get.

To find the correct location for your shrub, it is good to understand the windows in your house and which direction they are facing.

Continue on as we elaborate on the different directions that your windows are facing and the kind of light that they provide for your plants.

North-Facing Window

Windows that are facing to the north do not get direct sunlight. They are considered to be lovely cool and shaded areas with indirect sunlight, which makes them the perfect spot to grow low-light plants.

Placing indoor plants with low light requirements — such as ferns — in north-facing windows is perfect. Be careful, however, when winter starts.

During these colder months, you might have to provide supplemental lighting to your plants standing in a northern window with some extra light, as they will then receive even less light than they already do. Use a grow light — commonly used by hobby plant growers — or place them in a brighter window during winter.

Even low-light terrarium plants need enough light to grow.

East-Facing Window

An eastern window has the best of both worlds. It can provide plants with both direct or indirect sunlight.

During the early morning hours, east facing windows allow lots of direct sun to come through. But as the day approaches the afternoon, this light turns into bright indirect light.

Morning sunlight is great as the sun’s rays are not as intense or hot as the light of midday or afternoon. This makes it less likely for leaf burns to occur.

The ideal plants to place in an eastern window are those that thrive well in bright but moderate, indirect light. An east-facing window is ideal for most types of houseplants.

South-Facing Window

Opposite to the light of a north-facing window, the light that passes through a southern window is considered to be not only the brightest but also the most intense. This amount of ambient light makes it the perfect location for an indoor plant that requires good amounts of direct sunlight.

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The southern window stays full of light from the early morning hours up until the sun starts setting. It becomes quite hot in this window, so be extra careful with plants that are sensitive to too much direct sunlight. This type of light will easily scorch the green leaves of your house plant.

A lot of flowering plants need good amounts of sunlight in order to make their vibrant blooms and would therefore live well with southern exposure.

There are, however, flowering plants that thrive better in areas of low light. One example is the Peace lily. To be on the safe side, always research the light requirements of your flowering plants.

West-Facing Window

The light provided by west facing windows is opposite to the light received by an eastern window. The light coming through a west-facing window remains indirect during the first part of the day, turning into direct sunlight during the afternoon hours, beginning at mid-afternoon and lasting until the sun sets. This is a great setting for tropical plants, for example.

The direct sunlight coming through in the afternoon, means that it is less intense and less hot.

If you were to place your shrubs in a western window, you could expect that they receive about 3-6 hours of bright and direct light every day.

Be aware that the temperature in a west-facing window increases during the afternoon due to the direct rays of the sun. If your plants burn easily, simply move them a couple of feet away from the window.

Measuring Light Levels of Direct And Indirect Sunlight

If, after the above elaboration on different window directions, you are still unsure of how to classify different light levels in your home, there are some methods you can make use of to measure the light.

Continue on as we take you through two methods you can use to measure the level of light present in areas of your house.

Light Meter Method

A light meter is a tool that you can purchase or an app that can be downloaded onto your smartphone, which is able to estimate the amount of light in a given location, by measuring the number of foot-candles.

A foot-candle is a measure of illumination where one unit is equal to the light given off by one candle at a distance of one foot.

The light meter tool is used by first exposing the sensor of the gadget and then pointing it towards the direction of the light. It will then provide you with a reading of the light level in that specific location.

For a more accurate reading on the light meter tool, we suggest that you purchase a rapid response model. It has a rotating sensor which requires you to only aim at the direction that you want to measure.

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If you are making use of the light meter app on your phone, make sure that the settings are set for outdoor measurements. This also applies when you are measuring indoors. Measure the light by pointing the camera lens towards the window or any source of light that you wish to measure.

Understanding Sensor Readings

Continue below for a list of light meter range readings and their respective light levels. Starting from strongest to weakest light level:

  • 1000+ foot-candles (ftc): direct light
  • 500-1000 ftc: high level of indirect light
  • 100-500 ftc: moderate level of indirect light
  • 24-100 ftc: low level of indirect light

The Shadow Test

By analyzing the shadow that your plant — or any other object for that matter — casts during the brightest time of day, you can determine the level of light in a given location.

Seeing as the movement of the sun creates different light levels, this test should be done a few times throughout the day. Document the results of the tests and use the majority of the same outcome to determine the light levels of that area.

Different Shadows And Their Light Levels

Analyze the shadows and determine the level of light.

If you find that the object is casting multiple faint shadows with its outlines being unclear, you can categorize the light as being low. This kind of shadow appears when the sunlight does not hit the plant head-on.

An area of bright light would cast one or more medium-dark shadows with edges that appear slightly blurred.

If you find a well-defined dark shadow, you can classify the light as being direct sunlight.

Filtered Light

If you find that your house is lacking areas of low to moderate light for those plants that prefer indirect light, simply filter out the direct sunlight in order to create more indirect light indoors.

Using A Sheer Curtain

Put up a sheer curtain to block out any direct and harsh rays, This will still allow the sun to pass through, filling the area with bright indirect sunlight.

Using A Window Film

Window films are great at blocking UV rays. When applied to a window, this easy-to-apply film is able to block out 45-85 percent of sunlight, making it a more hospitable environment for house plants that thrive best in areas of indirect light.

Conclusion

This brings us to the end of this article covering direct vs indirect sunlight.

Remember to always study the plant care descriptions of the type of plant in question and then place them in a spot with the ideal level of sunlight.

We hope this helps!

References;

https://extension.missouri.edu/publications/g6515

https://play.google.com/store/apps/details?id=com.tsang.alan.lightmeter&hl=en&gl=US