How Different Colored Lighting Affects Different Plants

Posted by David Jones on

The variety of green and flowering plants in this world assures that everyone can find something to their liking that grows in their climate zone and can thrive under the particular circumstances of their specific home. And there are definitely different purposes for each type of plant, from bearing edible fruits to herbs and spices, medical purposes, and even just plain and simple beauty. But one thing is true of all plants – they require light to grow.

Of course, in nature, plants get sunlight, which provides the full spectrum of color, so many plants grow strong without any special care. At the same time, advances in science and technology have proven that specific colors of light serve a variety of purposes when it comes to plant growth. Understanding these basics can improve the growth of your plants over time, utilizing particular colors of light during certain stages to help produce the largest plants with the greatest health and highest yield.

A Quick Lesson in Light

Sunlight appears 'white' until you push it through a prism. This refracts – or fractures – the light into its color spectrum, otherwise noted as the 'rainbow'. The rainbow, however, is the basic primary range of colors, with others that are invisible to the human eye – infrared on the low frequency or 'red' end and ultraviolet on the high frequency or 'purple' end of the spectrum.


Every object absorbs most colors, leaving it to appear as the color (or combination of colors) that it does not absorb. For instance, a red flower is red because it doesn͛'t absorb the red light but does absorb all other colors from the spectrum. Tree bark appears brown likely due to not absorbing red, blue, and purple. It would take a very specific degree to be able to explain this fully, but basically, everything manmade and natural has a color or colors that are not absorbed, and thus we have the beauty of the world around us.
But colors don't just work for beautification purposes. Most colors have a purpose when it comes to plants, as well. And when you enter into horticultural, it can be extremely beneficial to know how every color of the spectrum will affect your plants and their growth so that you can put into practice a certain regimen and get the best results.

Why Are Plants Green?

As discussed, every object has specific colors that it does not absorb. Plants typically do not absorb green light from the spectrum, which causes the leaves and stems to appear green. While this is likely due to the chlorophyll produced in the process known as photosynthesis, it seems that chlorophyll does not absorb green.


Photosynthesis is the process plants use to create their own food for growth. Using light, they go through a process that creates sugar on which they feed, causing them to grow. During the process, plants utilize a combination of chlorophyll, light, and water to create food that has a green pigment, leading to their coloration, and generate the air that we breathe. It's a digestive process, much like all organisms have, with its own special configuration, and plants can grow stronger and fuller with specific types of LED grow lights provided at the right stages of growth.

Ultraviolet Light

Ultraviolet light(UV rays) is what activates pigment in our skin, causing us to tan. However, it's also detrimental to our health, leading to sunburn and shown to cause cancer. It's essential to realize that plants have weaknesses as well, and ultraviolet light, which is at such a high frequency it's invisible to the human eye, can damage plants in high quantities.


Of course, it has its uses, and you shouldn't deny your plants ultraviolet light. In fact, this part of the spectrum can actually cause your plants to produce anthocyan, a purplish substance that not only helps to protect your plants from damage due to UV light but also from detrimental micro-organisms.


However, you should carefully balance the amount of UV light your plants receive, as too much ultraviolet light can damage the plant DNA, its membranes, and its process of photosynthesis.

Far-Red or Infrared Light

At the other end of the spectrum is the invisible infrared light that we feel as heat on our skin. This is an interesting part of the spectrum in terms of its relationship to plants and growth. Unlike visible red light, plants reflect infrared light, which means that, when there is a high concentration of plants in a particular area, there is little infrared light available.

Plants use this to sense the density of plant population where they grow, which affects germination, or seed production. In fact, low levels of infrared light cause plants to 'pause' the germination process, noting that there is already a large population, and therefore, will not produce seeds under such conditions.
When this happens, you'll find that plants grow quickly, striving to outgrow their neighbors so they can reach above and gather more of the necessary light colors that help fuel the process of photosynthesis. However, this rapid growth in a competitive space can lead to your plants being weaker, with fewer flowers or fruit. In order to avoid this, you shouldn't use traditional incandescent light bulbs for plant growth, since they produce a great deal of infrared light and are not suitable for a high yield product.

Colors That Don't Matter

While use of green light with red can be productive, exclusively green light will do little for plants. This is because plants can only utilize colors to which they are sensitive, or for which they have receptors. These receptors – known as photoreceptors – are specific to colors in the spectrum and are found in the cells of plants, each one a pigment that is receptive of a certain color of light. Think of them as eyes that can only see one color and ignore all others in the spectrum.

Without photoreceptors for green light, there isn't much this color can do on its own for plant growth and production, but consider using it in combination with red light, which is essential during several stages of plant growth. On its own, green light will produce extremely weak vegetation that cannot survive to grow old and fruitful.

Yellow light also has no impact on plant growth, since plants do not absorb yellow light. In fact, a high concentration of yellow lighting, especially in the absence of more beneficial colors, can lead to slow growth or even the prevention of any growth.

While orange light doesn't have an effect on its own, plants tend to perceive it as red light and use it in the same manner. Violet and 'indigo' light are also colors that are absorbed and identified differently, typically seen by plants as blue light, another very important color of the spectrum for plant growth.

Red Light

Plants absorb red light through photoreceptors known as phytochromes, which are pigment that is blue-green in color. Red is perhaps the most vital of colors for all plants to receive in large quantities, since it is essential for size and important to the process of photosynthesis. 
Some of the areas in which red light are necessary include: 

 Hormone production – High levels of red light received during early growth produces meta-topolin, a hormone that prevents the breakdown of chlorophyll. This is precisely what a young 
plant needs to grow larger and stronger, since the chlorophyll is necessary in the process of 
photosynthesis in order to create adequate food (sugars) for the plant as it grows. The excess 
chlorophyll also keeps the plant very green, providing its health during this period. 
 Flowering and germination – Plants 'compare' the amount of red light to the amount of infrared light to determine if it should germinate or flower. If your plants are exposed to excess red light during the 'dark' period, you'll find that you'll have to wait longer to harvest from it, which is definitely not ideal. This is especially true of cannabis, which is part of the reason you'll find it ill-advised to enter the growing space during dark periods. 
 Seed type – Most growers want to produce female seeds (where applicable). While red light is incredibly important to the growth process, you don't want overexposure because too much red light can cause most seeds to grow into male seeds. 
 Flavor – For leafy greens, microgreens, herbs, and cannabis, you'll want to control the amount of red light based on the flavor you want to produce. Large amounts of red light produce larger amounts of certain oils, which can create a specific taste, usually causing
more bitterness in the flavor. While this may be desired in some plants, others will be less desirable. Determine your needs based on the types of plants you're growing.

Blue Light

Much like red light, plants have photoreceptors for blue light, called cryptochromes. As with red light, plants thrive with a good quantity of blue light, though exposure should be calculated differently during various stages of growth. For example, larger amounts of blue light may be beneficial during early stages of growth, as well as during the more 'dormant' periods of plant growth. Consider the following benefits of blue light on plants: 

 Hormone production – While red light produces a hormone that helps with photosynthesis, blue light decreases production of auxin. Auxin controls the growth of the stem as well as controlling the process of apical dominance, or the way a plant controls growth points and keeps buds from intertwining and creating a mess of excess branches. The overall effect of dampening auxin operation is that plants remain shorter and grow thicker and wider, which is 
what you want for sturdiness in the early growth stages. 
 Increased metabolism – The amount of blue light available to a plant determines how far the stomas – or pores in the epidermis or skin of the plant – open. These pores are used to take in carbon dioxide and release oxygen. With more blue light, the stomas are opened wider, which increases the metabolism of the plant, thereby accelerating growth and production. This is important during the flowering stage, creating more buds or flowers for harvest. 
 Growth direction – Blue light attracts plants, so you'll find that wherever the blue light is 
located, your plants 'reach' for it. This can help you assure that your plants are growing 'up'
in the direction you desire. 
 Multiplication and production – Leafy greens will be leafier, and all green will grow thicker with leaves when using the correct amount of blue light. In addition, when producing seeds, blue light will greatly increase your output (and support the output of female seeds where applicable and desirable). You'll find that, when you are lacking in blue light, you reap about 20 percent less in your harvest. This can be detrimental for herbs and especially for cannabis.

The Right Balance

While it is important to balance the full spectrum of light you use for plant growth, making sure you have the correct balance between the most vital colors – blue and red – will lead to the greatest production and healthiest plants. Typically, a 5:1 ratio of red light to blue will create sturdy, productive, mature plants that will germinate properly and produce an excellent crop for harvest. They will grow tall as well as thick, and you'll be able to keep them blooming and fruitful for a great many years.