Is Sunlight Through A Window Direct Sunlight For Plants?

Each houseplant has a different light requirement, and understanding the various types and dimensions of light is important for the best growth of plants. If you are wondering whether sunlight through a window is direct sunlight for plants, you are at the right place.

Sunlight coming through a south-facing window is very close to natural direct sunlight. However, the intensity of light coming from the east and west-facing windows is already low, and the glass from the window filters it down to about 50-75%, so it cannot be considered direct sunlight.

To understand whether your plants get direct sunlight through the window, you must understand the different types of sunlight and which direction gets what kind of light. Let’s understand.

Importance of light for plants

Through photosynthesis, plants absorb the sunlight they receive and convert it into energy they use to grow.

Plants that need full sunlight must be grown outdoors under the sun for their full growth, while houseplants are adaptable to grow in lesser sunlight.

They can grow in direct or indirect sunlight on the windowsill of our homes.

Also read: Do Indoor Plants Need Sunlight?

The different light levels

Understanding the lighting conditions to help your plants thrive can take time and effort.

While some plants cannot grow without a full day of direct sunlight, some can quickly get burnt if the sunlight is too strong.

In incorrect lighting conditions, plants do not show any warning signs immediately, but their growth and health decline over time.

This is why it is essential that you know which place in your house would be ideal for which plant.

Windows facing different directions have different lighting setups.

You can have a huge window and still not enough light if its direction is wrong or if there are obstructions outside.

So to make you understand the scenario better, I will discuss the different types of light and the role of each direction.

The most commonly discussed lighting types are direct, indirect, medium, and low.

Direct vs. indirect sunlight for indoor plants

Indoor plants are mostly adaptable to indirect light.

Direct light is where the sunlight directly falls on the plant through the window, which is required for plants that need direct sunlight, like cacti, flowering plants, variegated plants, etc.

Few homes in our modern apartments have access to direct sunlight.

Indirect light is what most indoor plants grow best in.

Though direct sunlight does not fall on the plant, the sun’s rays indirectly fall on something else before hitting the plant.

Such areas have bright light but not direct sun rays.

What is direct sunlight for plants?

Direct sunlight refers to unfiltered sunlight directly falling on the plants.

It hits the plant without any obstruction or barriers between the source and the plant.

Though it is more appropriate in outdoor setup, some homes have access to direct sunlight – like open balconies, patios or big glass windows, etc.

The south-facing windows have the longest access to direct sunlight unless there are barriers or obstructions outside the window.

East-facing windows get direct sunlight in the morning, and west-facing windows get direct sunlight in the afternoon.

Plants that require full-day direct sunlight, like fruits, flowers, and vegetables, cannot be grown on any other side except south-facing windows if it has full access to direct sunlight.

Most indoor plants do not need a full day of direct sunlight.

Too much direct sunlight can burn the leaves of your plants.

However, some plants with variegation require 3-4 hours of direct sunlight to grow.

Certain houseplants that prefer growing in indirect light can find direct sunlight damaging as it can burn their leaves.

Plants that require direct sunlight

Here are a few plants that thrive in direct sunlight:

• Most vegetable plants
• Succulents
• Begonias
• Hibiscus
• Desert rose
• Aloe vera
• Yucca
• Croton
• String of bead
• Jade
• Most flowering plants

What is indirect sunlight for plants?

Indirect sunlight is the light that passes through a filter before reaching the plant, like the leaves of a tree or a sheer curtain.

In nature, those plants that grow under bigger plants on forest floors in the wild are accustomed to indirect light.

Most houses in our modern-day compact apartments receive more indirect light than direct.

Most plants adaptable to partial or low light can live in indirect sunlight. 

Plants that thrive in indirect sunlight

Here are a few plants that prefer indirect sunlight:

• Calathea
• Ferns
• Alocasia
• Schefflera
• African violets
• Spider plants
• Orchids
• Snake plants
• Pothos
• English ivy
• Chinese evergreen
• Philodendron
• Peace lilies

Bright indirect light

In a window receiving direct sunlight, if there is a curtain or film, the light becomes bright indirect, or filtered light.

Also, if you move the plant a few feet away from direct sunlight, the light becomes bright indirect.

Here though the direct sun rays do not fall on the plant, they receive the sunlight’s warmth and brightness.

Variegated plants like pothos or philodendrons do well in bright indirect sunlight.

Also read: What Does Bright Indirect Light Mean For A Plant? (With Examples)

Indirect light vs. shade

Shade and indirect lights are similar terms used to denote spots where direct sun rays do not reach.

Outdoors shades are areas with barriers like trees and buildings that block the direct sunlight.

Technically all indoor spots are shades, as there are ceilings and walls to cover them from direct sunlight.

While buying indoor plants, buy the ones marked as shade-loving or indirect light tolerant.

What is partial sunlight?

Partial sunlight refers to locations that receive direct sunlight for only some parts of the day, around 4-6 hours.

For example, the eastern windows that receive direct sunlight during the early morning of the day remain shaded from the stronger intense afternoon sunlight.

Most foliage plants or variegated plants can be fine in partial sunlight, but flowering and fruit-bearing plants may find the light too less.

What is low light?

Low-light areas are where the natural sunlight is quite low, and you may need to turn up electric lights even in the daytime.

Think of rooms without windows or windows in high buildings or windows with trees outside that completely block sunlight from getting in.

Few plants, like the ZZ or snake plants, can adapt to low light conditions. 

Though their best growth occurs in more bright light, they can tolerate low light, but their growth will be slower.

How do I know if sunlight through the window is direct or indirect?

Understanding the lighting levels throughout the home can be difficult for a beginner or a novice.

You should use multiple scientific methods if you want to get a better understanding of the subject.

1. Shadow test: When the sun is bright, hold up your plant to observe the shadow that determines the light.

• Direct light will give a clear, well-defined shadow outline.
• Bright indirect light will cast a slightly lighter shadow with slightly blurry edges.
• Low light will result in a faint shadow with indistinct outlines.

Following the above test, you can position the plants according to the light situation of the plant.

2. Light meter: If you are one of those who only rely on scientific devices to show you the answers, a light meter is what you need to invest in.

It is a device that measures the number of foot candles, a unit to measure light intensity.

Set the light meter app on your phone, put it at the location you want to measure, and face the camera towards the light source.

The device will show the light level of the location.

The measurement of foot candles is as follows:

Light level	Measurement
Direct sunlight outdoors	5000+ foot candles
Direct sunlight indoors	2000-5000 foot candles
Bright indirect light	1000-2000 foot candles
Medium indirect light	500-1000 foot candles
Low light	250-1000 foot candles
Deep shade	50-250 foot candles

3. Plant growth/Appearance: You can determine the light levels by noticing your plant’s signs.

However, plants take months before showing the warning signs, so this not be very successful.

Plants in low light may show signs like:

• Leggy or sparse growth
• Smaller leaves
• Constantly wet soil
• Variegations turning green
• No new growth
• Bending towards the light source

Plants getting too much light show signs like:

• Sunburn
• Brown yellow edges
• Dry, crispy leaves
• Foliage color fading

Is light through my window direct sunlight?

Quite technically, sunlight through a window is not 100%direct sunlight.

The light shining through the window is partially obscured and refracted.

But in outdoor conditions, like open terraces, patios, and lawns, you can achieve direct sunlight without interference.

Outdoor plants that need full sunlight to bloom or grow might not survive in windows even if the sunlight hits the plant directly.

But for houseplants, direct sunlight in the windows can be sufficient.

It is because indoor plants are adapted to lower levels of light, and direct sunlight in the windows is the most intense and highest amount of light available indoors.

Impact of directions

Understanding the different directions and their impact on the plants is the best way to understand what kind of light they get.

South-facing windows – Direct sunlight

The south-facing windows in our homes in the Northern hemisphere have the brightest and most intense sunlight.

This is the idle place for any plants requiring maximum sunlight.

The south-facing windows also have sunlight from sunrise to sunset for the longest hours of the day.

The south-facing windows can become quite hot in certain areas when the summers are scorching and can lead to sunburn in the plants.

However, plants that thrive in full sunlight enjoy the southern windows. 

West-facing windows – Direct and indirect

West-facing windows get indirect sunlight in the morning and direct sunlight for about 4-6 hours during the afternoon.

Western windows are also quite warm, though not as hot as southern windows.

The intensity of the sunlight in the windows rises from the afternoon till sunset, as the afternoon sunlight is stronger than the morning sunlight.

Certain delicate plants get scorched during the afternoon if the sun is too hot, so you might need to provide filters to reduce the intensity of the hot sunlight. 

East-facing windows – Direct and indirect 

East-facing windows in the Northern hemisphere provide a perfect spot for most medium sunlight-requiring houseplants.

The eastern windows get direct sunlight in the first half of the day and indirect sunlight for the rest of the day.

The early morning sunlight in the eastern window through direct is much milder than in the south or west-facing windows.

This does not burn any of the plants.

However, plants requiring intense full-day sunlight do not thrive on the eastern windows.

Otherwise, for most foliage plants that survive in low, medium, or indirect sunlight, eastern windows are quite ideal. 

North-facing windows – Low and indirect

Homes or rooms with north-facing windows in the northern hemisphere have the least light.

They are cooler than the other directions and get no direct sun rays.

During summers, plants that thrive in the shade and low light stay comfortable in bright north-facing windows.

However, winters in colder regions can be too harsh in this direction.

You will need to add artificial grow lights to dispel the cold during winter and keep your plants warm if you do not want to move them to a sunnier place.

Even the low-light plants might show signs of stunted growth or wilt in northern windows, so you need to keep an eye on the plants there.

Which direction gets the most light?

For those residing in the northern hemisphere, a south-facing window gets the most light because it stays closest to the equator.

Similarly, a north-facing window gets the most light for those in the southern hemisphere.

South-facing windows are best for houseplants due to the bright light throughout the day, which helps almost all kinds of plants thrive.

However, if you live in a hot region and the sunlight is too burning for the plants, you may decide to shift it to other windows or put in some filters. 

What if the sunlight from the window is too direct for the plants?

Sometimes the direct sunlight during summer through the windows can get too strong for the plants, which can burn their delicate leaves.

Do not fret because there are multiple ways to filter the sunlight so that they become softer and indirect not to scorch the leaves.

• Sheer curtains: Putting up sheer curtains is an effective way to reduce the intensity of sun rays. It allows the warmth and light of the sun to get inside the room but reduces its intensity. Thus protecting the plants from burning due to too much sun. They do not cost a fortune and can be used to add an aesthetic element to the room.
• Move the plant away: If you think the sunlight is too intense, you can move the plant back a few feet from the window. This reduces the intensity of the sun hitting the plant. 
• Apply window film: Window films are easy to apply and block around 45-85% of the sunlight during the summer. They also help keep the homes cooler, thus improving energy efficiency by keeping them cooler in the summer.

Final words

Whether sunlight through the window is direct or indirect depends on the direction of the window. Any blockages between the sunlight and your plants can also determine this.

Most houseplants will not react well to intense direct sunlight, so make sure you protect them from such conditions. You can either use curtains or blinds to make the sunlight indirect or move the plants a few feet away from the window.

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Sources: University of Minnesota, David H. Trinklein, Horticulture State Specialist, The University of Georgia, The Royal Horticultural Society.