What Light Color is Best for the Plant’s Growth?

Indoor grow lights

For once, we all must have wondered why plants need light and how exactly different light colors help with their growth?

Let us share with you that plants absorb light for Photosynthesis, and the range of light colors play a vital role in helping the plants produce food and energy.

Plants grow well in full-spectrum lighting, a combination of blue and red wavelength (400-700nm) with smaller amounts of green, yellow, and Infrared wavelengths to help with Photosynthesis.

Pothos in Sunlight
The indoor plant taking in natural light (Source: Pexels)

Most growers imagine the light that mimics sunlight as the best source for plant growth, but it is not exactly true.

A plant will only use a few light colors emitted by the sun while offsetting the rest because some light colors are harder to absorb or simply redundant.

Therefore, you should know what different light colors are helpful to plant, especially if you intend to use artificial grow lights.

Does the Color of Light Affect Plant Growth?

The common question asked by growers is whether a light color positively affects the plant’s growth.

The answer is Yes!

One of the significant factors contributing to plants’ healthy growth is the light color.

Although the availability of carbon dioxide, watering, and a source of nutrition is equally essential, light colors play a vital role in ensuring the plant’s healthy growth.

photosynthesis process
A diagram of the Photosynthesis process (Source: Gifer.com)

Photosynthesis is a process that converts light and water into carbohydrates as a form of energy, which is then released to the rest of the plant for even growth.

A report by the University of Minnesota points out that without adequate light, carbohydrates cannot be manufactured, the energy reserves are depleted, and plants die.

However, the color of light more than the light itself will determine a plant’s growth.

The light that plants use for photosynthesis is called photosynthetically active radiation, which happens to be the same spectrum of light that we can see.

They absorb light colors by using pigments called chlorophylls, but they do not take in all of the available colors.

Plants naturally need more blue and red light colors to produce lush, green foliage, which helps regulate their growth by creating sturdy stems and assisting with chlorophyll production.

chlorophyll
Plants are perceived as green because chlorophyll absorbs mainly the blue and red wavelengths but the green light. (Wikimedia)

However, plants use different colored light for various purposes, and not all plants use the same amount of colored light.

Is the Wavelength of Light the Same as the Light Color?

Yes, it is the wavelength that gives different light colors.

It is from these wavelengths that plants get most of their energy.

Among all the visible light colors, red has the longest wavelength with 700nm, while blue is the shortest wavelength with 400nm.

Light Spectrum Wavelength
Light Spectrum Wavelength (Source: ScienceLearn.org.nz)

The longer the wavelength, the lesser the energy; hence, red has the least power among all the visible colors.

When all the color wavelengths are combined, they produce white light typical with sunlight or natural light source.

Do Different Light Colors do Different Things?

Although the plants are genetically programmed to grow solely using sunlight, many growers mistake white light that mimics sunlight as the best light source for the plant.

Instead, a plant only absorbs a few light colors emitted by the sun, depending on the plant type and growth stage, while reflecting the rest.

What is a Color Spectrum?

It is a graphical display of each color in the light visible to human eyes.

A color spectrum comprises all the light colors emitted by sunlight or ones you generally see in a rainbow.

According to Sciencing.com, a color spectrum consists of a rainbow of electromagnetic spectrum colors ranging from blue to red, with yellow, orange, green, and multiple variations sandwiched between them.

The light’s wavelength determines the color: the higher the wavelength, the hotter the color (Red), and the lower the wavelength, the colder the color (Blue or Violet).

Let us look at different light spectrum colors and how they impact the plant’s growth.

1. Violet (380-430nm)

Violet has the shortest wavelength but relatively high energy compared to other colors in the spectrum.

The wavelength ranges from 380nm to 430nm. When combined with blue and red light colors, it helps the plant attain its color and aroma.

The higher amount of energy emitted by violet color helps enhance plant color, fruiting, and vegetable.

Moreover, it may help enhance the flavor and the number of antioxidants in the plant stems.

2. Blue (430-500nm)

Blue is a cold, light color and one of the most critical light colors for plant growth.

With the short wavelength range between 430-500nm, it is readily available for absorption by chlorophyll.

Although one of the actual light colors that assist with Photosynthesis, it is not nearly as effective on its own as when combined with red.

A study concludes that, In addition, blue light regulates the opening of stomata, which are the tiny openings on leaves that control both water loss and the uptake of carbon dioxide.

Moreover, plants that quickly absorb blue light are usually compact and thicker with darker green leaves, preventing lanky stem growth.

3. Cyan and Green (500-565nm)

Cyan refers to greenish-blue with a wavelength range between 500-520nm, a combination of green and blue light colors.

Green, on the other hand as a wavelength range between 520-565nm.

Cyan and green are less helpful to chlorophyll, but they may help the plant reach its full potential.

Green is considered the least effective light color for plants’ growth.

However, the plant’s photoreceptors responsible for photosynthesis may absorb some green light for consistent growth.

4. Yellow (565-580nm)

Yellow is the most visible color of the light spectrum, but it is naturally the least used light color by a plant.

Plants absorb light yellow color to help with the photosynthesis process, but it may not be helpful in itself.

Especially, seedlings given yellow light color alone will not create carbohydrates and will fail to grow.

5. Orange (580-625nm)

Like yellow, orange is one of the most visible colors of the light spectrum that does not help much with the plant’s development.

Most plants quickly absorb orange color without doing much damage, so you need not worry about limiting their intake.

6. Red (625-740nm)

Like the color blue, plants mostly take in red to help with the photosynthesis process but may not be effective on their own.

Plants grown under red light solely may produce stretched, elongated appearance with thin leaves.

However, it will help the plant reach its flowering stage, mainly for maturation.

A report concludes that the pigment phytochrome mediates the flowering of plants with a photoperiodic flowering response.

It wonders when combined with a blue waveband, generally in the range of 5:1, to enhance foliage and flowering.

You should also note that the red wavelength usually promotes germination or seedling.

7. Far-Red (740-10,000nm)

Far-red or Infrared (IR) with 740-10,000nm is the longest wavelength from the visible light color spectrum.

It helps with the seedling or germination process, where the IR signals the seedling to start germinating and lessens the time it takes for the plant to flower.

It also passes through dense upper canopies to support the foliage growth on the underside of the plant.

The amount of red light relative to the amount of far-red radiation (R: FR) also has a pronounced effect on leaf expansion and stem elongation

8. UV Ray

The least effective of the light color wavelengths is the UV ray. Yet, it is the most damaging wavelength for plant growth.

A wavelength of anything under 380 may consist of Ultra Violet rays.

The high energy radiated by UV rays may quickly burn plant leaves and stems.

In a rare case, UV may help a plant, especially cannabis production. It triggers the plant’s stress response system to protect itself from abiotic stress; short-wavelength irradiation.

What Color of Light is Best for Plant Growth?

The colors blue and red are considered the best for a plant’s growth and development.

Chlorophylls quickly absorb these color combinations to produce food and energy for the plant; hence, directly helping with the photosynthesis process.

Plants enjoy a higher amount of red, up to 5 times as much as blue.

Blue wavelength helps with root development and strong stem growth, while red wavelength helps flowering.

However, blue has a relatively high amount of energy that can easily damage the plant’s growth with the shortest wavelength among the two.

Therefore, it needs to be carefully mixed with red to limit its overexposure. On the other hand, too much blue light may stunt the root proliferation and prevent vertical growth.

Color spectrum nM range
Color spectrum nM range (Source: GrowLightInfo)

Here is an exciting surprise for you!

Plants only use blue and red light colors for growth is a myth!

Plants are grown with 80-90%red light and 10-20% blue light helps achieve fuller plants with lush thick foliage and appropriate stem lengths.

You may find some artificial grow light to be purple, which contains a combination of red and blue lights.

It is known to be beneficial during the vegetative cycle of plant growth.

However, they emit a higher level of lumens, are quite expensive, and only emit a combo of red and blue, which may not be effective for even plant growth.

A plant requires a combination of various light colors throughout its life span.

Keep this in mind, especially if you are trying to grow plants with the assistance of artificial grow lights.

Color Spectrum for Grow Lights

Since red wavelengths are essential for plant growth to blue light, most grow lamps would contain more red than blue.

However, they should also compensate on other color spectrums for even plant growth.

As per LuminGrow, The light that plants predominately use for photosynthesis ranges from 400–700 nm, containing red, blue, yellow, and green wavebands.

Also known as Photosynthetically Active Radiation, these light wavebands help substitute the exact growing condition provided by natural lighting.

Photosynthetically Active Radiation
Photosynthetically Active Radiation (Source: CollegeDunia)

Q: Do the plants with different lighting requirements take the same amount of grow light?

Nope, they absorb the light in varying amounts and intensity depending on their need.

A whole sun plant with higher lighting requirements, such as Olive and Russian sage, should take more extended lighting than those with less lighting requirement.

Grow Lights Best for Plants

Grow lights do the same thing as the sunlight by providing a plant with different color spectrums to assist with photosynthesis.

There are three different types of grow lights available for plants.

These include fluorescent grow lights, LED grow lights, and High-Intensity Discharge lights.

1. Fluorescent Grow Lights

Compact fluorescent bulbs (CFLs) produce low heat levels and proper color temperatures ranging from 2700-10,000K.

The fluorescent growth lights are categorized into three types: T5, T8, and T12.

T5 is more efficient than T8 and T12. Although 40% smaller than T8 bulbs, they contain just as much more light.

T12 is an older generation fluorescent bulb effective as grow light but may require more maintenance than the rest.

A single bulb contains between 30 lm/W and 90 lm/w luminance, effective for growing young seedlings or plant starters.

However, the weak light intensity makes it less reliable as a primary light source. Hence, you can use them for supplemental lighting instead.

CFL grow light
CFL grow light (Source: Wikimedia)

2. HID Grow Light

High-Intensity Discharge (HID) was initially used to replace fluorescent bulbs before the advent of LED grow lights.

They produce significantly bright light with consistency.

HID grow lamp
HID grow lamp (Source: Wikimedia)

However, they are costly, consume a lot of electricity, and emit a lot of heat harmful to plants.

Although most HID grow lights were dumped for more energy-efficient LED grow lights, they are still in some places for large-scale growing.

You could find two different types of HID grow bulbs.

Ceramic Metal Halide (CMH) Grow BulbsHigh-Pressure Sodium (HPS) Grow Bulbs
Made from metal salts and mercury vapor, they produce white light that closely resembles natural sunlight.Made from high-pressure sodium, they produce extremely bright light with more reds and oranges.
Best for growing all kinds of plants in any vegetative stage.Best for growing flowers and fruits.
It uses up a lot of energy.It emits a lot of heat and soaring temperature.

3. LED Grow Lights

Light Emitting Diode (LED) is an eco-friendly choice compared to fluorescent.

Although they are considerably expensive than fluorescent, they tend to be more energy-efficient and significantly lower heat output.

LED light bulb
LED light bulb (Source: Wikimedia)

LED lightings are preferred as primary grow lights because they offer greater light intensity and varying light wavelengths appropriate for plant growth at different stages.

Some of the advantages of using LED grow lights include:

  • They are eco-friendly and energy-efficient.
  • They are more durable than primary lights because of continuous high light intensity.
  • In addition, they offer an ideal light spectrum range (400-700nm) required by the plants for growth.
  • You can customize them to emit different light wavelengths, from blue to red or in a combination, to influence vegging or flowering stages as per your need.

The energy-efficient grow lights, you can leave them on even for over 16 hours a day, without worrying about soaring energy bills.

Here are a few recommendations for LED grow lights.

LED LightsFeaturesImage
MARS HYDRO TS-1000 Led Grow LightA hydroponic grow light provides 3x3-ft coverage and offers dimmable full spectrum lamps.

It offers 660-665nm Red IR/3200-4200Knm/5200-6800Knm, close to natural light.
BESTVA Led Grow Light (2000 Watts)Hydroponic grow lamp with 5x4-ft coverage and full-spectrum lighting.

Choose from the VEG mode for vegging and BLOOM mode for flowering.
SPIDER FARMER SF-2000 (200 Watts)Hydroponic grow lamp with dimmable quality and 24-ft coverage.

It provides full-spectrum lighting between 660nm to 760nm.
MAXSISUN PB4000 (400 Watts)Hydroponic grow lamp with 4x4-ft coverage, remote controllable feature, and dimmable quality.

It provides between 660nm to 730nm color spectrum.

Note: Incandescent lights are good for lighting up a room but are less useful in helping with plant’s growth. They emit only about 10% of their energy as light while 90% is heat.

Factors Other than Color that Play a Role

However, the correct light color is not everything a plant requires for healthy growth and development.

Every plant has a different requirement for lighting for different stages of development.

Here are a few factors that equally contribute to plants’ growth.

1. Light Intensity

Not all plants need the same light intensity for healthy growth.

Plants such as Cacti and succulents have a higher need for high lighting intensity than other plants.

They would naturally require growing lights that offer high lighting intensity without the risk of burning their leaves.

Lux meter checking the light intensity
Lux meter checking the light intensity (Source: Amazon)

Otherwise, you can adjust the intensity as per your need by changing the settings, if there are any.

Alternatively, consider keeping your plant close to the light source to increase the effect of light intensity. Likewise, move them as far as the light source if they prefer moderate to low lighting.

The light level for normal office work is more common in the range of 500-2000 lux but it may significantly increase when used as the grow lights.

A low-light plant may need around 100-5000 lux, while a full-sun plant may need 35,000-60,000 lux of the light level.

2. Distance Between the Light Source and Plant

Determining how far to keep the light from the plant will depend on the grow light, wattage, and heat output.

HID produces more heat than LED and CFL; thus, they should be kept farther from the plant.

Grow LightsDistance
HID Grow Lights (400W)12”-19” away from the plant
HID Grow Lights (600W)14”-25” away from the plant
LED Grow Lights (240-400W)16”-30” away from the plant
LED Grow Lights (450-550W)20”-30” away from the plant
CFL (200W)6”-10” away from the plant

Here is an insightful video highlighting how far to keep your grow lights from your plants.

3. Light Duration

The duration of artificial lighting will entirely depend on the plant’s growth and requirement.

A vegging plant would require at least 12 hours of light each day, while a flowering plant would require 18 hours.

Light duration may depend on the plant type
The light duration may depend on the plant type (source: Unsplash.com)

Generally, the illumination duration for most houseplants ranges between 12 and 16 hours, with at least 8 hours of darkness.

The illumination ensures that the plant produces food and energy for its upkeep, while the darkness helps the plant break down the food and fuel for consumption.

4. Heat or Temperature

This is another crucial factor for the plant’s growth because a plant will fail to develop despite proper lighting when the temperature is too low or high.

Most foliage and flowering plants require between 70-80 degrees temperature during the day and 60-68 degrees at night.

Light Temperature Scale
Light Temperature Scale (Source: Wikimedia)

Although an LED grows light provides some heat to the plant, it does not necessarily compensate for the adequate heat required.

If your indoor plant has a higher heat requirement or growing a large number of plants, consider using HID bulbs that would be more effective than installing multiple LED and CFL bulbs.

Otherwise, place heat mats under the containers or heat lamps and programmable radiators around the plant to generate adequate heat required by the plant.

What Type of Grow Light is Best for Growing Plants Indoors?

As previously mentioned, plants prefer lighting that mimics the natural sunlight with an appropriate color spectrum (400-700nm).

If you are still confused, choose to grow lights that offer the best full-spectrum lighting, which provides a combination of red, blue, violet, yellow, and orange.

Moreover, ensure that your grow light produces a calm and warm light temperature that can be adjusted according to the plant’s needs.

Growing seedlings using grow lights
Growing seedlings using grow lights (Source: Unsplash)

To Sum it Up

Do not worry about matching the sunlight because plants do not take in all the light color spectrums produced by natural light.

Instead, you can focus on conditioning the lighting to match the correct color spectrum between 400-700nm that a plant quickly absorbs.

Better place your plants under natural sunlight to provide a conducive growing environment at no cost at all.

Otherwise, you can resort to appropriate grow lights at different times of the year to compensate for the lack of sunlight.

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