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Grow light spectrum guide.

Grow light spectrum is important for plant growth because different spectrums can affect photosynthesis and various stages of plant growth. Choosing the right spectrum for your plants can help optimize their growth and yield by giving them the right light for photosynthesis. This article will help you understand grow light spectrum and how to use it to maximize plant growth and yield.

What is Grow Light Spectrum?

Plants are biologically designed to grow using sunlight, which we perceive as white light, or yellow-tinged white light. It appears white because it contains all colors of the rainbow mixed. A color spectrum is a graphical display of each color in the light. The color wavelength, measured in nanometers, is displayed on the spectrum chart, with longer wavelengths appearing towards the red end and shorter wavelengths towards the violet end.

Grow Light Spectrum Chart

The term "grow light spectrum" refers to the range of electromagnetic wavelengths a light source emits to help plant growth. For photosynthesis, plants need light from the PAR (photosynthetic active radiation) region of wavelengths, which falls between 400 and 700 nanometers (nm). Nanometers are a universal unit of measurement used to measure the light spectrum. Humans can only detect visible light wavelengths (380-740nm), but plants can also detect ultraviolet and far red spectrums. Chlorophyll, the pigment responsible for photosynthesis, absorbs light primarily in the blue and red regions of the spectrum.

What are the types of growth light spectrum?

PAR, or photosynthetically active radiation

PAR is the light range vital for plant growth and photosynthesis. This spectrum includes blue, red, and green wavelengths. UV and infrared light are also sometimes included in a grow light spectrum.

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UV light spectrum (100–400 nm)

UV light spectrum can improve plant defense mechanisms and terpene production but can also damage plants if used excessively. Plants like cannabis may benefit from a small amount of UV light, as it can improve trichome development and enhance flavors and aromas. However, it's important to monitor the levels and ensure they don't exceed safe limits for your plants.

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Blue Light Spectrum (400–500 nm)

Blue, green and red light falls under the PAR light spectrum. This light spectrum is vital for vegetative growth and promotes healthy leaf development and chlorophyll production. Blue light can also improve plant defense mechanisms and increase essential oil production in plants like herbs. Moreover, it is also important for overall plant health and can improve the taste, smell, and appearance of fruits and flowers.

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Green Light Spectrum (500–600 nm)

While it may seem counterintuitive, green light is important for plant growth. It helps regulate the chloroplast and aids in photosynthesis. Green light can also improve the taste and smell of fruits and flowers. The green light should be combined with red and blue light for optimal growth and yields.

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Red Light Spectrum (600–700 nm)

Red light is crucial for the flowering stage, as it promotes bud development and increases yields. It can also enhance flavors and aromas in fruits and flowers. In addition, red light can benefit plants' immune systems and improve essential oil production in herbs. The red light should be used in conjunction with blue light for optimal plant growth.

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Infrared light spectrum (700-1,000 nm)

Infrared (IR) light can increase plant vitality and essential oil production. Another benefit of infrared light is its ability to penetrate deeper into the plant's tissue, making it a useful supplement for plants with thick foliage. Also, infrared light can improve the effectiveness of other wavelengths and stimulate cell growth. However, too much-infrared light can damage plants and result in burnt tips. Therefore, it's important to monitor the levels and adjust as needed.

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Download our complete guide to choose the best grow lights for indoor plants

Grow light spectrum chart

Grow light spectrum chart displays the relative power of each wavelength, allowing you to compare different grow lights and choose one that best suits your plants' needs. In general, the range of PAR (Photosynthetic Active Radiation) is 400-700nm. Chlorophyll absorbs light in this range for photosynthesis. This chart can be found online or in grow light product manuals. It's important to remember that the chart is just a guide, and each plant may have different light spectrum needs. For example, blue light promotes leaf growth with tomatoes, while red light promotes fruit production. On the contrary, red light promotes leaf growth for lettuce, while blue light slows it down.

How to choose the right grow light spectrum?

Choosing the right grow light spectrum for your plants can be overwhelming, but there are a few things to consider. First, consider the stage of growth your plants are in and choose a grow light spectrum accordingly. Next, consider the type of plant you're growing and the spectrum they need for optimal growth. Finally, ensure that the grow light emits wavelengths in the PAR range to promote photosynthesis.

Grow light spectrum charts can also help you choose the right grow light for your plants. These charts display the relative power of each wavelength, allowing you to compare different grow lights and choose one that best suits your plants' needs.

Full-spectrum LED lights are a convenient option for providing balanced spectrums throughout the different stages of plant growth. However, they may be pricier and harder to find than broad-spectrum grow lights.

What is Full Spectrum Lighting?

The peak of photosynthetic efficiency in most plants falls around the red and blue spectrums, but it's also important to have a balanced spectrum that includes some green, yellow, and far red light. This is where full spectrum LED grow lights come in. A full-spectrum LED grow light is a convenient way to give your plants the balanced spectrum they need throughout their growth stages. It eliminates the need for purchasing and switching out different grow lights as your plants progress through their life cycle. These lights often have adjustable spectrums, allowing you to fine-tune the light for your specific plants' needs.

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What is Broad Spectrum Lighting?

Broad spectrum grow lights are not as precise as full spectrum lights and emit a broader range of wavelengths. They can be effective for general plant growth but may not be as optimized for specific plants' needs. One advantage of broad-spectrum lighting is that they are often cheaper and easier to find than full-spectrum lights.

Nonetheless, broad-spectrum grow lights may emit UV and infrared light, which can harm plants if used in excess. So it's important to monitor the light levels and ensure they don't exceed safe limits for your plants.

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Full Spectrum LED Lighting

Full-spectrum LED lighting is now widely used in crop production because they emit wavelengths in the PAR range, allowing for optimal photosynthesis. They also have the ability to replicate natural sunlight and provide adjustable spectrums for different stages of plant growth. Full spectrum LED lights are also energy efficient and have a long lifespan, making them a cost-effective option for growers. Also, LED lights emit less heat, reducing the need for ventilation systems and lowering the risk of plant stress or damage. Moreover, they don't contain harmful gases like HID lights. These LED lights don't emit as much heat, reducing the need for ventilation systems and lowering the risk of plant stress or damage.

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Grow Light Spectrum and Cannabis

Cannabis plants have specific light spectrum needs at different stages of growth. The vegetative stage requires mostly blue light, while the flowering stage requires more red light. Full-spectrum LED grow lights can provide a balanced spectrum for both stages and optimize photosynthesis for healthy plant growth and high yields. However, it's important to note that cannabis plants are sensitive to excessive light and may require lower light levels than other plants. Also, because of their unique light spectrum needs, it's important to carefully monitor the level and intensity of light during the flowering stage to prevent plant stress and maintain high-quality buds.

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Should I use a different light spectrum for different plants?

Different plants have different light spectrum needs and may not thrive under the same lighting. It's important to research your specific plants' light requirements and adjust the grow light spectrum accordingly. Full-spectrum LED lights offer versatility and the ability to fine-tune the spectrum for each type of plant, making them a convenient option for growers with a diverse range of plants. On the other hand, investing in lights with tailored spectrums for each may be more effective if you have a small number of specific plant types. It's ultimately up to the grower to determine their plants' needs and choose the right lighting option.

How Does the Grow Light Spectrum Guide Compare to the Use of Plasma Grow Lights in Horticulture?

The grow light spectrum guide provides valuable information for horticulturists looking to optimize plant growth. However, the future of horticulture may see a shift towards plasma grow lights. These innovative lights offer a wider spectrum of light, leading to enhanced photosynthesis and potentially higher yields for growers. Plasma grow light future horticulture looks promising.


Choosing the right light spectrum for your plants can seem daunting, but with a bit of research and understanding, you'll be able to provide them with optimal lighting for healthy growth and bountiful yields. Full-spectrum LED lights offer versatility and can tailor the spectrum for each plant, while specialized grow lights may work better for specific plant needs. Ultimately, it's up to the grower to determine their plants' requirements and select the best lighting option.


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