Understanding Light Spectrum and LED Grow Lights

Understanding light spectrum can be a little tricky due to the vast amount of information out there, but it's also essential when selecting the correct grow lights for your applications. If you've researched grow lights, you've likely read information about PAR values, color temperature and maybe even seen graphs and charts demonstrating what spectrum a particular grow light produces.
Unfortunately, much of this information goes unused or untrusted, thanks to a lack of understanding and in some cases mis-representation by light manufacturers.

However, at TSRgrow, we've been exhaustively researching and studying the light spectrum for years and have developed our LED grow lights to offer the greatest spectrum for optimal plant growth.

Still, we don't just expect you to take our word for it. Let's explore together what the light spectrum is, how it affects your indoor or greenhouse horticultural applications, and how we've designed our lights to maximize your plants' true potential.

What is the Light Spectrum?

The term light spectrum refers to the band of electromagnetic radiation which is visible to the human eye. Though the electromagnetic radiation spectrum is incredibly broad, and all of it can be considered "light" in some regard, most of it is invisible to humans. The visible light spectrum consists of those bands of electromagnetic radiation whose wavelength vibrates at a frequency that can be interpreted by our eyes.

Measured in nanometers (nm), the visible light spectrum is actually relatively narrow, occurring between the wavelengths of 380-760 nm, though waves at either end of the spectrum may be difficult or impossible to see.

At the lower end of the visible light spectrum, around 400 nm, is violet light, and beyond the visible spectrum on this lower end, we find invisible ultraviolet light. On the other end, around 660-700 nm, we encounter red light; beyond the visible range on this end, we find far-red and infrared light, also invisible to the human eye.

While we think of the visible light spectrum as encompassing all light that we can see with our eyes, plants interpret light differently. Understanding how plants react to light throughout the spectrum is important when selecting grow lights, as the spectrum produced by grow lights can fluctuate significantly from model to model and brand to brand.

How the Light Spectrum Affects Plant Growth

Plant-Response-Light-Spectrum-1Plants utilize a wide spectrum of light, ranging from ultraviolet to far-red and everything in between. Unfortunately, many grow light manufacturers only account for specific wavelengths of visible light, between 400-700 nm. This spectrum of light is referred to as Photosynthetically Active Radiation (PAR), so-called because it is the spectrum of light that plants can use for the process of photosynthesis or the conversion of light energy into growth. Chlorophyll, the molecule responsible for photosynthesis, tends to absorb light from the blue and red spectrums best, both present in PAR lighting.

There is mounting evidence that light beyond PAR wavelengths is also critically important to plant growth and health - far red as an example can help trigger flower development when used in the right ratio to red (660nm). There is evidence that plants do make use of UV and far-red light, but to what degree it is just now being learned and studied in more depth.

Additionally, plants interpret various colors of light from throughout the spectrum as signals to begin different stages of growth. While it is well-known that shortening a plant's photoperiod, or the amount of time it receives light each day, can induce flowering, it is not as commonly understood that the onset of the bloom period is dependent upon the light spectrum as well.

Here is a quick breakdown of various light spectra and the colors with which they correspond:

  • UV light (100-400 nm) - Ultraviolet light, as any beachgoer knows, can cause significant tissue damage in humans through prolonged exposure. The same is true for plants: too much UV light can cause damage. In moderation, though, UV light has been shown to have surprising benefits: increase in color and aroma while also proving beneficial to fighting microbes and pests.
  • Blue light (400-500 nm) - Blue light is essential for vegetative growth, as it signals the plant to produce dense and thick foliage and aids in CO2 uptake.
  • Green light (500-600 nm) - Though not as significant in photosynthesis as blue or red light, green light still plays a role in a plant's metabolic processes and should be supplemented. Unlike other colors, green light possesses the ability to penetrate a plant's canopy and is useful for working on plants during their night period.
  • Red light (600-700 nm) - Red light is the most absorbable by chloroplasts (cells responsible for photosynthesis), making it crucial to all stages of plant development. Increased red light, however, is crucial to flowering.
  • Far-red light (700-850 nm) - Though beyond the visibility of our human eyes, plants still make use of far-red light, interpreting its presence as a signal to spur on shoot and stem development, as well as to trigger flowering.

In natural sunlight, plants receive a changing spectrum of light as the year wears on. During the summer, when the sun is at its peak, the majority of the sun's rays pass through the atmosphere, signalling to outdoor plants that it is time to build lots of dense foliage and fortify for the coming bloom.

As the sun dips lower in the coming autumn sky, more of the sun's blue light is reflected away by the atmosphere, allowing for greater penetration of red light to plants. Outdoors, plants interpret this increased red light as a cue to begin flowering; indoors, this cue must be provided by the grower.

This is why, with traditional high-intensity discharge (HID) horticultural lighting, growers were forced to switch bulbs as they transitioned their plants from one growth phase to another. These changes are always an effort to emulate natural lighting and the shifting of seasons. Since different bulbs emit different spectrums, it was formerly necessary for a grower to accommodate their plants by offering up bulbs that contained greater amounts of red spectrum light, typically high-pressure sodium bulbs.

Thanks to significant advancements in LED grow lighting technology, these adjustments and bulb switches are now nearly obsolete.

The Spectrum of LED Grow Lights

Every light source will produce its own unique spectrum of light. Full-spectrum light from the sun contains all wavelengths within the visible light spectrum, but for horticultural lighting purposes, achieving a full spectrum of light can be extremely difficult. It's important to consider the conditions in which your plants will be growing when selecting a lighting setup, as many factors may influence the necessary lighting conditions, such as whether your grow room is fully indoors or you're growing in a greenhouse.

Fortunately, our LED grow lights can be attuned to any circumstance no matter how you are growing.

LED grow lights boast the specific advantage of being able to incorporate various colors into a single unit. This is particularly poignant to cannabis growers, as it allows for the incorporation of additional light spectra beyond those contained within a standard diode.
TSRgrow's LED lights contain far-red and UV diodes to aid plants in receiving the necessary non-visible light.

The inclusion of various spectra into a single light allows the grower to enhance their plant's blue light saturation during vegetative growth and red light saturation during flowering. Switching to TSRgrow LED lighting systems can spare the grower the troubles of climbing on ladders precariously perched above their canopy, as well as eliminating the need to ever change bulbs again.

Selecting the Correct LED Grow Lights

The best LED grow light is the one that produces the best crops and highest yields with the greatest efficiency. While lighting must be combined with many other elements for a successful grow, choosing the best lights possible makes it easy to maximize your production.

At TSRgrow, we've made it our mission to offer the highest quality LED lighting to our customers. Our lights are capable of producing a full spectrum of light tuned to plants, allowing growers to tailor our lighting solutions to fit their needs. With our Lighting as a Platform (LaaP) technology and remote power servers, we've made the customization and automation of our products even easier by incorporating critical environmental monitoring and control functions.

With a wide variety of products and configurations, we've put complete control of the grow room, not just the lighting, back in the hands of the grower. Be sure to check out our TOTALgrow Solution to see how we can help you design the best, most efficient LED lighting solution for you. 

If you have any questions about light spectrum or TSRgrow's advanced LED lighting solutions, please visit our website or contact a growing specialist today.


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