How Many Hours A Day Does A Greenhouse Need Sun?

Imagine having your own greenhouse, filled with lush plants and flowers thriving under the perfect amount of sunlight. But you may be wondering, just how many hours of sunlight does a greenhouse need each day? In this article, we’ll explore the ideal amount of sun exposure for greenhouse plants and uncover some helpful tips to ensure their healthy growth. So sit back, relax, and get ready to learn all about the essential sunlight requirements for your very own greenhouse oasis.

Factors Affecting Sunlight Requirements

When it comes to greenhouse gardening, providing the right amount of sunlight is crucial for the growth and development of your plants. Several factors influence the sunlight requirements of plants in a greenhouse. Understanding these factors will help you create the optimal growing conditions for your crops.

1. Plant Type

Different plants have varying sunlight requirements based on their natural habitats and characteristics. Some plants are sun-loving and thrive in direct sunlight for a significant part of the day, while others are shade-tolerant and prefer filtered or indirect sunlight.

Understanding the specific sunlight requirements of the plants you are growing is essential for achieving optimal growth and yield. Sun-loving plants such as tomatoes, peppers, and cucumbers require at least 6-8 hours of direct sunlight each day. On the other hand, shade-tolerant plants like lettuce, spinach, and herbs can thrive with less sunlight and may only need 3-6 hours of direct sunlight.

It is important to research the sunlight needs of the specific crops you are growing in your greenhouse and plan your greenhouse setup accordingly.

2. Season

The season in which you are growing your plants also affects their sunlight requirements. The intensity and duration of sunlight vary throughout the year, and plants need different levels of sunlight at different stages of growth.


During the spring season, the days are gradually getting longer, resulting in increased sunlight exposure for your plants. However, the intensity of sunlight may still be lower compared to the summer months. It is crucial to monitor the sunlight hours and make adjustments to provide adequate light for new seedlings or young plants.


Summer is characterized by longer days and higher intensity of sunlight. Most crops thrive during this season and require a significant amount of sunlight. However, it is important to ensure that excessive heat and direct sunlight do not cause heat stress or scorching of the plants. Implementing shading techniques and proper ventilation becomes essential during the hottest summer days.


As the days become shorter in the fall, the sunlight hours decrease. This reduction in sunlight availability can affect the growth and development of your plants. Prioritize providing supplemental lighting or consider transitioning to shade-tolerant crops during this season.


Winter is the season with the lowest sunlight levels in many regions. Depending on your geographic location, you may experience shorter daylight hours and less intense sunlight. Providing adequate lighting with artificial sources becomes crucial to meet the sunlight requirements of your plants during this season.

3. Geographic Location

The geographic location of your greenhouse has a significant impact on the amount of sunlight it receives.


The latitude at which your greenhouse is situated affects the angle of the sun’s rays and the number of daylight hours. Greenhouses located closer to the equator receive more direct sunlight throughout the year, while those located near the poles receive less sunlight, especially during the winter months.


Altitude also plays a role in sunlight availability. Higher-altitude locations may receive more intense sunlight due to decreased atmospheric interference. However, extreme altitudes can also have adverse effects on plant growth, such as increased UV exposure and temperature fluctuations.

Your greenhouse’s geographic location determines the amount of sunlight it receives, and considering these factors can help you plan and adjust your greenhouse setup accordingly.

4. Greenhouse Orientation

The orientation of your greenhouse plays a crucial role in maximizing sunlight exposure. Proper orientation ensures that your plants receive the optimal amount of sunlight throughout the day.

North-South Orientation

Greenhouses with a north-south orientation receive more uniform sunlight exposure throughout the day. This orientation allows for maximum sunshine coverage, especially when the sun is at its peak. It also minimizes the risk of one side of the greenhouse blocking sunlight from reaching plants on the other side.

East-West Orientation

Greenhouses with an east-west orientation provide different lighting conditions throughout the day. They receive more intense morning sunlight from the east, which can be beneficial for certain crops. However, they may also experience more shading in the late afternoon when the sun sets in the west.

Partial Shade Areas

In some cases, your greenhouse site may have areas with partial shade due to nearby structures or trees. It is important to plan your greenhouse layout accordingly and ensure that these shaded areas do not obstruct sunlight from reaching your plants. Utilizing shading techniques or considering alternative locations for more light-sensitive crops may be necessary.

5. Greenhouse Covering Material

The material used to cover your greenhouse affects the amount and quality of sunlight that reaches your plants. Different covering materials offer different levels of light transmission and diffusion.


Glass is a traditional greenhouse covering material that provides high light transmission and clarity. It allows most of the sunlight to pass through, providing excellent lighting conditions for plants. However, glass may not offer as much light diffusion compared to other materials.


Polycarbonate is a popular greenhouse covering material known for its durability and light-transmitting properties. It offers good light diffusion while still allowing a significant amount of sunlight to pass through. Polycarbonate panels can help reduce the intensity of direct sunlight, which can benefit plants that are sensitive to excessive light or heat.


Polyethylene is a lightweight and cost-effective covering material commonly used for temporary or smaller greenhouses. While it provides good light transmission, it may not offer as much durability or insulation compared to other options. Polyethylene might need to be replaced more frequently to maintain optimal light transmission.


Acrylic is a versatile and transparent material commonly used in greenhouses. It offers good light transmission and durability. Acrylic panels can provide diffused light, reducing the intensity of direct sunlight and allowing for more even distribution of light throughout the greenhouse.

Shade Cloth

Shade cloth is a versatile covering material that can be used to filter or reduce the amount of sunlight that reaches your plants. It comes in various densities, allowing you to customize the shade levels based on your plants’ needs. Shade cloth can be particularly useful in regions with high temperatures or intense sunlight.

Choosing the right greenhouse covering material is crucial to ensure your plants receive the appropriate amount of sunlight while protecting them from excessive heat or harsh environmental conditions. Consider the specific needs of your crops and the climate of your region when selecting the covering material for your greenhouse.

6. Shading and Light Diffusion

In addition to adjusting the amount of direct sunlight that reaches your plants, shading and light diffusion techniques can help create a more optimal growing environment.

Natural Shading Techniques

Natural shading techniques involve using natural elements to filter sunlight. This can include strategically planting trees or erecting structures to provide shade during the hottest parts of the day. Utilizing shade-loving plants or trellises can also help create shaded areas in the greenhouse.

Artificial Shading Techniques

Artificial shading techniques involve the use of materials or devices to filter or reduce the amount of sunlight reaching your plants. This can include applying shading paint or installing shade cloths or screens. These techniques are particularly useful in regions with high temperatures or intense sunlight, allowing you to control the amount of light your plants receive.

Light Diffusion Benefits

Light diffusion refers to the scattering of light throughout the greenhouse, reducing the intensity of direct sunlight. Diffused light creates more even lighting conditions and helps prevent excessive heat and shadows. This can improve plant growth and reduce the risk of sunburn or heat stress. Greenhouse coverings that offer light diffusion, such as certain types of plastics or acrylics, can be beneficial for creating a more balanced light environment.

7. Artificial Lighting

In cases where natural sunlight is limited or insufficient, supplemental artificial lighting can be used to meet the sunlight requirements of your plants.

Supplemental Lighting

Supplemental lighting involves using artificial light sources to provide additional light for your plants. This is particularly important during the winter months or in regions where sunlight hours are limited. Supplemental lighting can help make up for the lack of natural sunlight and ensure that your plants receive the necessary light for photosynthesis and growth.

Photoperiod Extension

Photoperiod extension refers to artificially extending the daylight hours using artificial light sources. This technique can be used to manipulate the flowering or fruiting stages of certain plants that require specific day lengths to initiate flowering. By extending the photoperiod, growers can control the timing of blooming and harvest.

Grow Lights

Grow lights are specialized artificial light sources designed to provide the specific light spectrum required for plant growth. They produce light that closely resembles natural sunlight and can be adjusted to suit different crops and growth stages. Different types of grow lights, such as fluorescent, LED, or high-pressure sodium (HPS) lights, offer varying levels of energy efficiency, light spectrum, and intensity.

Types of Artificial Lighting

There are various types of artificial lighting options available, each with its advantages and considerations. Fluorescent lights are energy-efficient and suitable for starting seedlings or providing general illumination. LED lights are highly efficient, have a long lifespan, and can be customized to emit specific light spectrums. High-pressure sodium (HPS) lights are known for their intense light output and are often used in commercial greenhouse settings.

Consider the specific needs of your plants and the cost-effectiveness of different lighting options when incorporating artificial lighting into your greenhouse setup.

8. Temperature and Humidity

Temperature and humidity levels within a greenhouse can impact the sunlight requirements of your plants. Understanding these factors will help you create the ideal growing environment.

Temperature Requirements

Different crops have specific temperature requirements for optimal growth. While sunlight is necessary for photosynthesis, excessively high temperatures can lead to heat stress and negatively affect the overall health of your plants. Monitoring and controlling the temperature within your greenhouse is crucial to ensure your plants thrive. Proper ventilation, shading techniques, and temperature management systems, such as fans or evaporative cooling, can help regulate the temperature and create a more favorable environment for your plants.

Humidity Requirements

Humidity levels also play a significant role in plant health and growth. Some plants thrive in high humidity environments, while others prefer drier conditions. Maintaining the appropriate humidity levels within your greenhouse can support the health and growth of your plants. Tools such as humidifiers or dehumidifiers, along with proper ventilation, can help you regulate humidity levels.

Effects of Temperature and Humidity on Sunlight Needs

Temperature and humidity levels influence the rate of evaporation and transpiration in plants. Higher temperatures and low humidity can accelerate moisture loss, increasing the plant’s demand for water. This, in turn, affects the plant’s ability to utilize sunlight efficiently. By managing temperature and humidity levels, you can ensure that your plants have the optimal conditions to make the most of the available sunlight.

10. Crop Stage

The sunlight requirements of your plants may vary at different stages of their growth and development. Understanding these variations is essential for effectively managing your greenhouse.

Germination and Propagation

During the germination and propagation stages, plants require sufficient light to support healthy root development and early growth. Providing the appropriate amount of light during this stage can help promote robust seedling growth and increase the chances of successful establishment.

Vegetative Growth

During the vegetative growth stage, plants require adequate light to support leaf and stem development. This is the stage where most of the photosynthesis takes place, and plants need a balanced level of sunlight exposure to maximize their growth potential.

Flowering and Fruiting

The flowering and fruiting stages are critical for many crops, as they determine the yield. During these stages, plants require an appropriate balance of light and darkness to trigger and support the flowering and fruiting processes. Adjusting the photoperiod using supplemental lighting techniques can help ensure that plants receive the necessary amount of light to initiate and sustain the flowering and fruiting stages.


Dormancy is a stage during the plant’s life cycle when it goes into a resting phase, often triggered by changes in temperature and light. Some plants, particularly those grown in colder climates, go dormant during the winter months. During this stage, reduced sunlight levels are usually acceptable, as the plant’s metabolic processes slow down and the focus shifts to energy conservation.

Understanding the specific sunlight requirements of your crops at each stage of growth can help you implement appropriate lighting and gardening techniques to optimize plant health and yield. It is advisable to research the specific needs of the plants you are growing and seek guidance from experienced growers or horticultural experts to ensure the best results.

In conclusion, providing the right amount and quality of sunlight is essential for successful greenhouse gardening. Factors such as plant type, season, geographic location, greenhouse orientation, covering material, shading techniques, artificial lighting, temperature, humidity, greenhouse design, and crop stage all influence the sunlight requirements of your plants. By understanding and effectively managing these factors, you can create the optimal growing conditions for your crops and maximize their growth, health, and yield in the greenhouse.

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About the Author: Jake Scott