Introduction

Choosing the right spectral range to promote healthy plant growth requires considering the photosynthesis needs and growth stage of the plant. Photosynthesis is the process by which plants convert light energy into chemical energy, in which different wavelengths of light have different effects on plant growth and development.

Generally speaking, plants have higher requirements for red and blue light. Red light (wavelength range of 610-720nm) promotes flowering and fruiting of plants and can extend the flowering period1. Blue light (wavelength range of 400-500nm) helps plant growth and leaf formation. Therefore, when choosing a spectral range, make sure to include red and blue light.

Different plants have different light needs at different growth stages. For example, during the growth stage of a plant, blue light is more important for the growth and development of seedlings, while red light is more important for flowering and fruit development. Therefore, the spectral range can be adjusted according to the growth stage of the plant to meet its specific needs.

This article will introduce the spectrum and explain how the spectrum affects plant growth, list the spectral parameters, and then teach our readers how to use the right light color to promote plant growth.

Understanding the Light Spectrum

Full-spectrum LED lights are based on the understanding of how various light wavelengths influence plant health and growth. Plants primarily use light for photosynthesis, a process in which they convert light energy into chemical energy to promote development. Different light wavelengths elicit specific responses in plants, including:

Blue light (400-500nm): Encourages vegetative growth, ensuring plants remain strong and compact.

Red light (600-700nm): Boosts the flowering and fruiting stages, leading to more vibrant blooms and increased yield.

UV light (280-400nm): Stimulates the production of protective substances, helping plants resist pests and diseases.

IR light (700-1000nm): Supports efficient photosynthesis and overall plant metabolic processes.

How A Light's Spectrum Affects Plant Growth

Different wavelengths have different effects on plant growth and development, and on stimulating and controlling the differentiation of plant tissues and organs. Therefore, the solar spectrum determines the external morphology and internal structure of plant organs to a certain extent, and plays a role in morphological construction. In addition, different wavelengths of light also have an impact on the photosynthetic products of plants, such as red light is conducive to the synthesis of carbohydrates, and blue light is conducive to the synthesis of proteins and organic acids.

The Spectrum of LED Grow Lights

Spectrum is the pattern in which the dispersed monochromatic lights are arranged in sequence according to their wavelength (or frequency) after the complex light is split by a dispersion system (such as a prism or grating). The full name of the pattern is optical spectrum. The largest part of the spectrum, the visible spectrum, is the part of the electromagnetic spectrum visible to the human eye. Electromagnetic radiation in this wavelength range is called visible light.

Full spectrum: Full spectrum refers to the spectral curve that includes ultraviolet light, visible light and infrared light. The red, green and blue ratio of the visible light part is similar to that of sunlight, and the color rendering index is close to 100. The spectrum of sunlight can be considered as the full spectrum.

Effects of different wavelengths of light on plant growth:

280 ~ 315nm: Minimal impact on plant morphology and physiological processes.

315 ~ 400nm: Chlorophyll absorption is low, affecting the photoperiod effect and preventing stem elongation.

400 ~ 520nm: (blue) Chlorophyll and carotenoids have the largest absorption ratio and have the greatest impact on photosynthesis.

520 ~ 610nm: The absorption rate of the pigment is not high.

610 ~ 720nm: (Red) Chlorophyll has low absorption rate and has a significant impact on photosynthesis and photoperiod effects.

720 ~ 1000nm: Low absorption rate, stimulates cell extension, affects flowering and seed germination.

＞1000nm: converted into heat (infrared light, thermal effect).

Visible light wavelength range: 380-780nm

The wavelength range corresponding to each monochromatic light is:

Purple light 400~435nm

Blue light 450~480nm

Blue light 480~490nm

Blue green 490~500nm

Green light 500nm~560nm

Yellow green 560~580nm

Yellow light 580nm~595nm

Orange light 595~605nm

Red light 605~700nm

Chlorophyll mainly absorbs red light and blue-violet light. Carotenoids mainly absorb blue-violet light, and absorb less light of other wavelengths, with green light being the least absorbed. So the color of the leaves we see is green.

Invisible light, such as ultraviolet light of a certain intensity, can also promote plant growth. Long ultraviolet rays can stimulate plant growth, increase crop yields, and promote the synthesis of proteins, sugars, and acids. Exposure to ultraviolet light can increase the germination rate of seeds.

What Color Light Is Best for Plant Growth?

For optimal plant growth, blue light and red light are the most important colors in the light spectrum.

Blue Light (400–500 nm):

Promotes vegetative growth (leaf development).

Helps plants produce chlorophyll, which is essential for photosynthesis.

Encourages strong, healthy stems and leaves.

Often used in the early stages of plant growth, such as germination and seedling development.

Red Light (600–700 nm):

Essential for flowering and fruiting.

Encourages plants to bloom and produce fruit.

Works well in combination with blue light for overall growth.

Full-Spectrum Light:

A mix of blue, red, and sometimes other colors (like green and yellow) provides a natural sunlight effect.

Many grow lights are designed to mimic natural light for more balanced plant growth across all stages.

In general, combining both blue and red light is considered the best approach for most plants, with blue light being especially crucial for vegetative growth and red light for blooming and fruiting.

Final Thoughts

When choosing LED grow lights, it's important to match the spectrum to your plants' special needs at each growth stage. Graceehomes LED grow lights offer a balanced spectrum with red, blue, white, and IR light, making them ideal for all stages of growth, from seedling to harvest. With different red-to-blue ratios, growers can select the best option for optimal results. Mars Hydro also offers targeted spectrum lights, including UV and IR, for specific plant growth needs. Explore our LED Grow Lights collection and contact us for more details.