Grow Light Color Temperature – What is The Best For Plants?

Last Updated on January 31, 2023

Are you ready to learn about growing light color temperatures for plants? Let’s get started. When it comes to indoor hydroponic gardening, one crucial aspect is the growth light color temperature. A grow light provides plants with light that mimics natural sunlight so that the plants can still be able to carry out all the processes required for photosynthesis to facilitate growth and development.

For plants in hydroponics to grow well, you need to get the right to grow light color temperature for the specific growth stage they are at.

It can be quite confusing to understand these different light requirements. However, all hydroponic growers need to understand all your plant’s light needs. This is why we will be enlightening you on color temperature, light spectrum pigments, their requirement for various plant growth stages, and more. So, read on to learn.

The Light Color Spectrum

Let’s talk about the color spectrum of sunlight. Normally, plants make use of natural sunlight to photosynthesize, when planted where they can access it. The colors we see sunlight produce are usually white light or yellowish-white light.

These white colors the sunlight produces are a mix of several colors of a rainbow and the mixture gives the white or yellowish-white colors. Therefore, the graphical display of all these colors is known as the light color spectrum.

Sunlight Color Spectrum

Grow Light Color Temperature

Plants develop and progress throughout their life cycle from the seedling stage to the vegetative phase, flowering, and then to the fruiting phase. Therefore, different colors of light are required for all these stages of a plant’s life cycle.

The grow light color temperature comes in different hues of spectrum required for your various plant growth stages.

The color temperature of any light source is the tones or colors of light seen by the human eye. We measure the light from the bulb of these grow lights by color temp and color temperature is measured in degrees Kelvin.

Kelvin Scale Of Temperatures

Let’s take a look at the Kelvin scale which is expressed in color temperature. From the Kelvin scale, we can see the soft tones of the red light spectrum at the lower end. These red light tones are required for the flowering and fruiting phases of the plant’s growth cycle.

Kelvin Scale Of Temperatures

There is the tone of the blue light spectrum on the other end of the Kelvin scale. The vegetative phase of a plant requires this light. Grow light such as HID and fluorescence makes use of this scale.

Grow Light Color Temperature: HID & Fluorescence Grow Light

HID (high-pressure sodium and metal halide) lights are the traditional grow lights we know of. They are pretty different from LED grow lights in that they don’t give out single colors the way LED lights do.

For these HID and fluorescence grow lights, the light they emit usually has yellowish soft hues. The grow light fluorescence bulb has its color temp as either cool white (which has more blue hues) or warm white (which has more red hues).

Grow Light Color Temperature: LED

LED grow lights are one of the most precise types of lighting. This is because they will supply you with the exact or accurate grow light color temp your plants need. The LED grow light will offer your plants a full spectrum. This implies there’s no stress of changing the lights as your plants progress through their flowering and fruiting stages.

PARFACTWORKS RA1000w LED Grow Light Hydroponic Full Spectrum

An appropriate LED should possess these colors for all your plant life cycle in the right measurements: Red LEDs (600 to 700 nm), Blue LEDs (400 to 500 nm), white LEDs, and infrared LEDs (700 to 800 nm).

Light Color Spectra Pigment That Plants Use

Plants make use of light for the photosynthesis process and this is made possible by some chemicals or pigments present in the plant leaves. Examples of these pigments include Chlorophyll A and B, carotenoids, etc.

So, let’s take a look at what some of these pigments do with light:

  • Chlorophyll: plants are quite rich in chlorophyll. Chlorophyll is one crucial pigment that plants use for photosynthesis. They use chlorophyll and light energy to produce plant energy for use in growth and production.
  • Carotenoid: another abundant chemical or pigment found in plants is the carotenoid. It works hand in hand with chlorophyll. They help plants absorb light at the same time sending the energy back to chlorophyll. Carotenoid also serves as protection for chlorophyll from photodamage especially when the plant is predisposed to too much light.

3000K vs 4000K grow light, Which One is Better For Plants?

Two of the most popular color temperatures for grow lights are the 3000K and the 4000K. The 3000K is slightly warmer than the 4000K. The colors of the 4000K are also slightly warmer but still yellow. If we put the two lights side by side, the 3000K has a slightly darker tone of yellow-white light, while the 4000K appears to have a lighter shade. 

So when is the time to use 3000K and when to use 4000K lighting? Both lights produce relatively warm light, but if your plants are in the vegetative and flowering phases, the 3000K light is better suited. If you only need the light for the vegetative stage of growth, then the 4000K lighting is the best of the two options. Both lights will work well, but the 3000K is better for encouraging flowering.

Lights in the 3000K and 4000K are great for plants as they are slightly cooler. Anything beyond 4000K and the blue color starts dominating, which is not ideal for the vegetative and fruiting stages of plants. Lights with 5000K and 6000K are closer to white, daylight color light.

Best Color Temperature For Grow Lights

Light is electromagnetic energy that is measured in wavelengths. Interpreting it this way just makes it easier to make distinctions between the different regions of the wavelengths, by assigning color temperatures to them to understand their different roles or functions in plants. To better understand the relationship between color temperature and wavelength, you can read more here.

So why is light important to plants and why do they have different preferences for the color of the light? Well, color affects plant growth in different ways. As we have already mentioned, blue light is important for vegetative growth while red light helps to promote flowering and fruit production. The color temperature of a grow light helps you to understand whether the output of the grow light leans more toward blue or red.

While plants primarily use the blue and red light spectra, there is research that suggests that some species of plants perform best with the full spectrum of light. This may suggest that it can be helpful to choose a grow light that has the full spectrum for your plants. 

Choose a full spectrum to grow light that has a color temperature in the blue (in the range of 5000 – 7000K) for the vegetative phase of growth and a color temperature in the red range (5000 – 7000K) to help promote the fruiting and flowering phases of growth.

When you purchase your grow lights, remember that different plants have different Kelvin preferences for growth, so if you are unsure, it might be best to consult a grow light specialist who will be able to provide more insight and help make you more comfortable with your purchase.

Conclusion – Grow Light Color Temperature

The plant life cycle will require the various color of light for different stages of the life cycle. All hydroponic gardeners need to know about growing light colors and their suitability for the different stages of growth, so they can get the best production out of their plants. 

So, we do hope you have learned some things on grow light color temperatures.

Happy growing!


What is the best color temperature for grow lights?

The best color temperature for growing plants is between 4,000K and 5,500K. The range of light that a plant needs to survive is 4,000K to 8,000K. This range is called the "thermal optimum" range. Plants are much more sensitive to light than you might think. For example, if you move a plant from a low light setting to a bright, high light setting, it will usually not die, but it may have to adapt.

If you are unsure of what color temperature to use, just use the color temperature on a light that is as bright as you can get it. You do not need to worry about the color temperature. As long as the light you are using is in the thermal optimum range, your plants should be fine.

If you move a plant from a high light setting to a dimmer light setting, it can die. This is why we often see plants in florescent lights, which provide very little light, and grow more vigorously than they would if they were in regular fluorescent lights. If your plant is getting too much light, or is receiving no light at all, it will stop growing.

What kind of light source should I use?

LEDs are an excellent option for growing plants because they last longer than HID and CFLs. You can purchase LED bulbs in both high intensity and low intensity. Low intensity bulbs provide lower light output, but are more efficient.

High intensity bulbs provide higher light output, but are more expensive. The most important thing to consider is the number of watts you need. LEDs have a lifespan of 25,000 hours. This means that you can use them for 20 years or more if you use them sparingly. LED bulbs also have better heat dissipation. CFLs and HIDs have a lifespan of 1,000-2,000 hours. If you have a room with no ventilation, you may want to use HIDs or CFLs.

What does color temperature mean?

The color temperature (K) of a light bulb is the perceived color of the light as compared to the other colors in the spectrum.

For example, a 3000K light is orange/yellowish and will warm up the color of your plants. A 5500K light is more blue/purple and will cool the plant down. The difference between the two would be like going from a 4000K light bulb to a 2000K light bulb. The same goes for the grow tent, which is probably similar to having a 4000K grow light but without the ability to adjust it. You could also get a grow light with an adjustable color temperature and use it in conjunction with a grow tent that has an even higher color temperature.