How the Color Spectrum Affects Plant Growth
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What Type of Light is Essential for Healthy Plants?

Companies that manufacture LED grow lights have a lot of different ideas about what types of light are needed during the growth process, and while we’ve looked at the idea of how different types of light affect plant growth elsewhere on this site I thought it would be a good idea to take a closer look at this topic. The sun itself doesn’t discriminate between different types of light – it simply emits its light and how living things on the earth process that light is entirely up to them. It turns out plants are quite particular in which parts of the light from the sun they use during the photosynthesis process and that’s what we plan on taking a look at here.

At the lower end of the visible light spectrum are lights in shades of blue; as you move towards longer wavelengths of light eventually you get to the red end of the spectrum. Most people working with indoor plant operations are more familiar with blue and red lights, but it’s a good idea to understand how the overall color spectrum affects plant growth. If we start at the blue end of the spectrum and move towards the red we’ll get a good idea of how light in different parts of the spectrum influence plant growth.

Blue Light

Blue light is essential at the beginning of a plant’s growth cycle as this is the type of light that plants first absorb to help with chlorophyll production. Your plants need lots of blue light during the seeding process and right through the first part of their growth cycle to ensure healthy roots, strong stems, and healthy leaves as well. Without blue light your plants will never get out of the ground, so any lighting system that you put together should include a healthy dose of exposure to this type of light.

Purple Light

As we move up the light spectrum you move into purple light, and while this may not be familiar to most of us it can certainly help your plants to grow. Purple light has a much shorter wavelength than red light and it can be just as effective in helping your plants through the vegetative growth process as blue light. This type of light is very energetic and that energy can be used by your plants, although it won’t be overly effective by itself.

Green Light

While there has been some debate recently on the merits of green light during a plant’s growth cycle there’s a good reason plants normally have green leaves – that’s because they are least effective at absorbing this type of light. In general, plants use less of the green light they absorb than any other part of the spectrum and that’s why your plants appear green, but that doesn’t mean they don’t use any green light at all during the photosynthesis process. Some green light is retained by your plants for photosynthesis; leaving this part of the spectrum out altogether can negatively affect the growth of the plants.

Yellow or White Light

Yellow light isn’t the most effective part of the spectrum for plant growth, but it is still present in sunlight and so it’s still important to ask the question of how plants use yellow light during the process of photosynthesis. It turns out there are a lot of people that are convinced it doesn’t do much at all and that by removing yellow light altogether from your indoor grow lights you can actually produce plants that are healthier than plants grown outdoors. This is certainly debatable, but what is certain is that yellow light is one of the least effective parts of the spectrum during your plants’ growth cycle.
It might seem intuitive to assume that yellow and white light are close to each other on the spectrum, but that’s not the case at all. White light is actually made by combining other colors on the spectrum such as red, green, and blue. Therefore white light will actually be much more beneficial for the photosynthesis process than yellow light.

Red Light

Red light has longer wavelengths than blue light and is therefore a lot less energetic. It’s important that your plants are exposed to red light during the blooming or flowering stages, but this type of light is not essential during the vegetative stage of your plants growth – in fact if you were to use only red light during the initial stages of the plants growth cycle your results would not be very positive at all. It’s best to use red light towards the end of the growth cycle in combination with some blue light as well.

A Full Spectrum of Light

For the healthiest plants you really need to include light from right across the color spectrum. While it’s true that certain types of light may be more effective at different stages of the growth cycle, your plants still need light from across the spectrum at any stage of their growth. If you concentrate your light too much on one end of the spectrum you probably won’t like the results.

Focused Intensity

If you expose your plants to higher concentrations of certain types of light at different ends of the growth process you’re likely to get the best results. As we’ve mentioned elsewhere on this site and touched on in this article as well, blue light is very effective during the vegetative stage of the plants growth cycle, but you should introduce more red light during the blooming stage.

Different Light at Different Stages

Understanding how the color spectrum affects plant growth may seem a little overwhelming at first, but once you get the basics down it’s pretty straightforward. Essentially, there are different types of light that are more important at different times during the plants growth cycle. In an indoor grow operation you can manipulate the type of light your plants are exposed to in order to optimize their growth; just don’t eliminate other light altogether at any stage and you should be just fine.

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