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What light is best for plants to grow in

Pink grolys lamp
The best light for plants is sunlight, but if the sun is absent, artificial light, and here's a full spectrum white grow light, the most similar to sunlight. 
 
The right light and brightness are crucial for plant growth and development. It is necessary for photosynthesis, the process by which plants convert light energy into chemical energy in the form of glucose.
 

In this article, I will explore the different types of light, their pros and cons, and how they affect plant growth.

The goal is to provide a clear understanding of what light is best for plants to grow in.

Basics about Light and Plants

Photosynthesis is a process that takes place in the leaves and stems of plants. It requires light, water and carbon dioxide to produce glucose and oxygen. Light is needed to activate chlorophyll, the green pigment in plants that absorbs light and uses it to convert carbon dioxide and water into glucose.

There are two main types of light sources that can be used to grow plants: natural sunlight and artificial light.

sunflower field

Sunlight as a source of light

Natural sunlight is the most ideal light source for plants, as it contains all the colors in the light spectrum (from 400nm to 730nm) that are necessary for plant growth. It is also free and easily accessible (in summer).

Benefits of natural sunlight

Natural sunlight is the most ideal and efficient light source for plants for several reasons:

  1. It contains all colors in the light spectrum: Sunlight contains all the colors in the light spectrum, from ultraviolet to infrared. This is important because plants use different parts of the spectrum for different processes. For example, plants use blue light for leaf and stem growth and red light for flowering and fruiting.
  2. It is free and easily accessible: Sunlight is a natural resource that is available everywhere and requires no cost. This makes it an economically viable option for plant cultivation.
  3. It has the right balance between light intensity and duration: Sunlight has a natural cycle of daylight and darkness that plants have adapted to over millions of years. This makes it the most natural and healthy light source for plants.

Although natural sunlight is the best light source for plants, it is important to note that it is not always available or appropriate. For example, in the winter months or in areas with very cloudy weather, it may be necessary to supplement with artificial light. In addition, some plants may require specific lighting conditions that cannot always be met by natural sunlight alone.

Disadvantages of natural sunlight

Although natural sunlight is the most ideal light source for plants, there are some disadvantages to consider:

  1. It is not always available: In some parts of the world, especially in northern and southern regions, daylight is very limited during the winter months. This makes it difficult for plants to get the necessary amount of light to grow properly. In addition, in some areas there may be periods of very cloudy weather, which also limits the amount of sunlight that reaches the plants.

  2. It may be too intense for some plants: During the summer months, especially in tropical and subtropical regions, sunlight can be extremely intense. This can cause damage to plants that are not adapted to such conditions. For example, too much direct sunlight can cause leaf burn, dehydration and even permanent damage to the plant.

  3. Micro greens: Direct sun will dry out the tender plants in a matter of minutes if planted directly in the sun. Microgreens can thus be grown with advantage under artificial grow lights. 

These disadvantages make it necessary to take precautions when growing plants in natural sunlight. It may be necessary to supplement with artificial light during periods of limited daylight, or to provide shade for plants that are sensitive to intense sunlight. It is also important to choose plants suitable for the light conditions available in your area.

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Artificial grow light

Artificial light as a source of grow light

Artificial grow lights are a good substitute for natural sunlight, especially when sunlight is not available. There are different types of artificial light, such as fluorescent light, LED grow light and incandescent lamps.

Advantages of artificial light

Artificial light has several advantages that make it a valuable resource for plant growing:

  1. It is available all year round: Regardless of the season or the weather, artificial light can always be supplied to your plants. This is particularly important during the winter months or in regions where daylight is limited for long periods.

  2. It can be controlled in terms of intensity and duration: With artificial light, you have full control over the light intensity and how long the plants are exposed to the light. This makes it possible to tailor the light conditions exactly to the needs of your plants and can help to optimize their growth and development.

  3. It can be adjusted to match the optimal light spectrum for a specific plant type: Different plants have different needs for light spectrum. For example, some plants need more blue light, while others need more red light. With artificial light, you can adjust the spectrum of light to suit the specific needs of the plants you grow.

These advantages make artificial light a very useful resource for plant cultivation, especially when natural sunlight is insufficient or unavailable. However, it is important to use artificial light correctly to avoid damaging the plants. For example, too high light intensity can cause leaf burn, and too long light duration can cause stress on the plant. It is also important to choose the right type of artificial light, as some types of light can produce too much heat.

Disadvantages of artificial light

Although artificial light has many advantages, there are also some disadvantages to consider:

  1. It can be expensive to buy: Quality light sources and the necessary equipment to operate them can be expensive to acquire. This includes the cost of the light sources themselves, as well as the cost of installation and the necessary equipment such as reflectors, ballasts and timers.

  2. Expensive to operate due to high electricity prices: Operating artificial lights requires electricity, which can be expensive, especially if you grow many plants or need to provide light for long periods of time. This is particularly a disadvantage in areas where electricity prices are high.

  3. It can produce heat that can damage plants if not managed properly: Some types of artificial light, such as incandescent lamps and some types of halogen lamps, produce a significant amount of heat. If this heat is not managed properly, it can cause damage to the plants, such as leaf burn or dehydration.

These disadvantages make it necessary to take precautions when using artificial light for plant cultivation. It is important to choose the right type of light source, control the heat correctly and take into account the costs of both acquisition and operation. It is also important to consider whether the advantages of using artificial light outweigh the disadvantages in your specific situation.

DLI for plants, learn about light for plants

Light Spectrum and Its Meaning

Light spectrum refers to the different colors or wavelengths of light. Plants use different parts of the light spectrum for different growth processes. For example, plants use the most blue light and Red light for photosynthesis, while green light is reflected by the upper layers of the plant, and thus provides photosynthesis in the deeper layers of the leaves and the plant, which is why plants look green.

Without the green light, you will get a plant that becomes more frail and does not develop as many leaves, which therefore cannot perform at its best.

Optimal light spectrum for plants

The optimal light spectrum for plants varies depending on the plant type and growth stage. In general, plants need more blue light in the growth phase to avoid too much stretching and more red light in the flowering phase.

Having said that, virtually all plants thrive quite well underneath white full spectrum light in all growth phases.

Light intensity and its effect on plants

Light intensity refers to the amount of light hitting a surface per second. unit of time. It is usually measured in lumens if people or PPFD – photons per square meters per second if plants. Too high or too low light intensity can have a negative effect on plants.

The effect of too low light intensity

The effect of too low light intensity on plants is clear and can have serious consequences for their growth and development:

  1. Slow growth: Insufficient light intensity means that the plants cannot carry out photosynthesis efficiently. Photosynthesis is the process by which plants convert light energy into chemical energy in the form of glucose, which is necessary for growth. Without sufficient light, the plants will not be able to produce enough energy, resulting in slow growth.

  2. Weak and thin stems: Plants will stretch towards the light source if the light intensity is too low. This results in long, thin and weak stems as the plant uses its energy to grow in height instead of developing a strong trunk.

  3. Stretch: This is a phenomenon where plants grow longer stems in an attempt to reach a better light source. This is a clear sign that the plant is not getting enough light. Stretching results in weak plants with thin stems and smaller leaves.

  4. Small leaves and flowers: Insufficient light intensity will also affect the development of leaves and flowers. Plants that do not get enough light will often have smaller leaves and flowers as they do not have enough energy to support their development.

These effects show how important it is to ensure that your plants receive sufficient light intensity. It is important to consider the location of your plants, the type of light source, and the amount of light they receive each day.

The effect of excessive light intensity

Excessive light intensity can have harmful effects on plants:

  1. Burnt or discolored leaves: Overexposure to light can cause damage to the plant's leaves, resulting in burnt or discolored areas. This affects the plant's ability to carry out photosynthesis and thus its ability to produce energy.

  2. Premature aging of the plant: As with too long light duration, too high light intensity can speed up the plant's aging process. This can result in a plant that looks older than it actually is and may not produce as many flowers or fruits as expected.

  3. Decreased photosynthesis due to damage to chlorophyll: Chlorophyll is the pigment in plant leaves that absorbs light and uses it for photosynthesis. Too much light can damage the chlorophyll, reducing the plant's ability to carry out photosynthesis and thus produce energy. Seen especially with lamps that only consist of red and blue diodes (pink light).

It is therefore important to control the light intensity correctly to ensure healthy growth and development of plants. This may involve using shade cloth or adjusting the distance between the light source and the plants.

Note, however, that when using white full spectrum grow light this problem is rarely seen, as it penetrates further into the leaf end and where the energy is deposited evenly over the entire plant.

Light duration and its influence

Comparison of different light sources

Light duration refers to the amount of time a plant is exposed to light during a 24-hour period (read more here DLI – Daily Light Integral). It is also known as photoperiod. Different plants have different needs for light duration.

The importance of light duration

  1. Affects plant growth and development: Plants use light for photosynthesis, the process by which they convert light energy into chemical energy in the form of glucose. This is necessary for the growth and development of the plant. If a plant does not get the required amount of light (DLI), it will affect its ability to produce energy and thus affect its growth and development.

  2. Affects flowering and fruiting: Light duration also affects a plant's flowering and fruiting cycle. Some plants, known as short-day plants, flower when the days are short and the nights are long. Other plants, known as long-day plants, bloom when the days are long and the nights are short. There are also plants that are day neutral, meaning that their flowering is not affected by the duration of light.

It is important to understand the light needs of the specific plants you are growing and to adjust the light duration accordingly. For example, if you are growing a long-day plant, make sure it gets enough light each day to promote flowering. If you are growing a short-day plant, you may need to limit the amount of light it receives to promote flowering.

The effect of too short light duration

The effect of too short light duration on plants is significant:

  1. Insufficient Photosynthesis: Light is essential for photosynthesis, the process by which plants convert light energy into chemical energy. If a plant does not receive sufficient light, it will not be able to carry out photosynthesis efficiently, resulting in insufficient energy production.

  2. Slow growth: Inadequate energy production due to insufficient photosynthesis will result in slow growth. The plant will not have enough energy to support healthy growth and development.

  3. Lack of flowering or fruiting: Light duration affects a plant's flowering and fruiting cycle. If a plant does not get the necessary amount of light, it can prevent it from flowering or setting fruit.

It is therefore important to ensure that plants receive the necessary amount of light each day to support healthy growth, flowering and fruiting.

The effect of too long light duration

The effects of excessive light duration on plants include:

  1. Stress on the plant: Plants need a period of darkness to rest and repair themselves. Constant lighting can cause stress on the plant as it does not get a chance to rest.

  2. Premature aging of the plant: Constant exposure to light can accelerate the plant's aging process. This can result in a plant that looks older than it actually is and may not produce as many flowers or fruits as expected.

  3. Decreased photosynthesis due to overexposure to light: Although light is necessary for photosynthesis, too much light can actually slow down the photosynthesis process. This is because too much light can damage the chlorophyll in the plant's leaves, which is necessary for photosynthesis.

It is therefore important to find the right balance between light and dark for your plants to ensure healthy growth and development.

Natural sunlight is the best light source for plants, as it contains all colors in the light spectrum and has the right balance between light intensity and duration. But it is not always available and sometimes it can be too intense for some plants.

Artificial light is a good substitute for natural sunlight, especially when sunlight is not available. It can be controlled in terms of intensity and duration and can be adjusted to match the optimal light spectrum for a particular plant type. But it can be expensive to buy and run, and it can produce heat that can damage plants if not managed properly.

Tips for choosing a light source for your plants

When choosing a light source for your plants, consider the following factors:

  • The type of plant and its light requirements – See PPFD & DLI.
  • Growth stage of the plant – sprouts, growth phase or flowers/fruit.
  • The availability of natural sunlight.
  • Your budget – Buy quality, cheaper in the long run.

In general, it is best to use natural sunlight whenever possible and supplement with artificial light when necessary.

Frequently Asked Questions (FAQs)

Which light is best for my plants?

Natural sunlight is the best light source for plants, as it contains all colors in the light spectrum and has the right balance between light intensity and duration. However, if natural sunlight is not available, artificial light is a good substitute.

Is artificial light harmful to my plants?

Artificial light can be harmful to plants if not controlled properly. Too high a light intensity or too long a light duration can cause stress on the plant and reduce photosynthesis.

How much power do grow lights use?

A 100-watt grow light lamp that is on 10 hours a day uses 1 kilowatt-hour (kWh) per day (100 watts x 10 hours = 1,000 watt-hours, or 1.0 kWh). If you pay DKK 2 per KWh, you thus use DKK 2 per day on having your lamp on.

Conclusion

Light is essential for plant growth and development. Natural sunlight is the best light source for plants, but artificial light is a good substitute when sunlight is not available. It is important to choose the right light source for your plants and manage the light intensity and duration correctly to ensure optimal growth and development.