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Growing marijuana under LED lights: Spectrum and wavelengths

In recent years the popularity of LED bulbs for growing marijuana has increased. But whether these bulbs can produce the best lighting for our cannabis?

With the growing popularity of LED bulbs for growing, manufacturers and distributors tend to invent new ways to capture your attention. They like to mix some real science with a healthy dose of marketing in the hope that they will tarry long enough to impress you with the latest exaggeration. There are so many terms thrown around, so it's hard to separate reality from exaggerations for marketing purposes.

When it comes to LED lights, one of the common ways that marketers try to get the customer's attention is by talking about The wavelength of light And on Spectrum.

Here's a simple list of what's important and what's less, to help your LED grow to its full potential.

LED lamp spectrum

When dealing with light, the term "spectrum" simply refers to the wavelength range of visible light from the entire electromagnetic spectrum. Besides the visible light, the electromagnetic spectrum includes various forms of energy (radiation): radio waves, microwave, infrared, ultraviolet, X-rays and gamma rays.

The plant uses mainly the blue and red parts of the spectrum
The plant uses mainly the blue and red parts of the spectrum

Incidentally, the plural form of the word Spectrum is spectra rather than Spectrums.

In any case, growth lamps use mainly the visible spectrum, and sometimes the spectra are used in the infrared and ultraviolet regions.

Wavelengths of growth lamps

In terms of LED growth lamps, or any other light for that matter, the term "wavelength" refers to the distance between peak and low points in a wave. Light wavelengths behave in a manner similar to waves in water and peaks can be close or distant from each other.

This is the feature (distance between points) that determines which light is visible: from red (long wavelength) to blue (short wavelength). Any shade of light along the visible spectrum can be measured in nanometers in the range of 380nm to 780nm, from purple / blue to red, respectively.

The energy from the visible spectrum is all that plants need to perform photosynthesis and grow. The knowledge of the reaction of the plants to the different wavelengths is the basis for the development of LED growth lamps.

How LED growth lamp promotes growth

Although the high-pressure lamps tend to have a certain edge of the spectrum (red - HPS / NGL, and blue - MHL / lade metal), they emit light throughout the spectrum exactly the same way a normal light bulb is. In general, plants will always respond to all wavelengths, but will maximize the benefits of blue and red wavelengths. Accordingly, they will see low benefit in the yellow and green wavelengths reflected back.

Notice the color differences in this LED light
Notice the color differences in this LED light

At first, the makers of LEDs thought that all that was needed was a single wavelength of blue and a single wavelength of red - at different stages of growth - that would give success. This method did work with limited tests on simple plants such as grass, but failed (or resulted in undesirable results) in more complex plants such as tomatoes and, of course, cannabis.

This did not stop some manufacturers from selling in the first days of the tumor lamps from badly designed models, which is why this industry is still trying to break itself off from the bad reputation created.

Required field / spectra and wavelengths for LED growth lamps

The first users of LEDs saw them as promising potential and luckily continued pushing the technology further. What they found was that the first models were at least partly complex - they had the correct ratio of red / blue - but they failed at the level of practical performance.

It was found that additional wavelengths were required to atone for the faults of the primary models. When you look at an active photovoltaic (PAR), you can see clear peaks in the visible light from which the plants use most of the energy for the photosynthesis process. It is clear that blue and red are needed, and until further research was done, it was estimated that orange light was also needed. The fact is that all that is needed are two wavelengths in the red field and two wavelengths in the blue field to provide the plant 95% of the energy it needs for all stages of growth and flowering.

Some manufacturers also add ultraviolet and infrared to increase Resin output And inflorescence.


There are six main photosynthetic pigments in vascular plants (cannabis in them) that drive growth, flowering, and reproduction. Different pigments in the plant absorb wavelengths at different points on the visible spectrum - red and blue together - in the growth and flowering stages.

For example, let's take the most common pigments in the plant, chlorophyll A and B. The absorption range of chlorophyll A is also between 400 and 450 nm (purple / blue) and between 650 to 700 nm (red and deep red) and chlorophyll B between 450-500 and 600-650 Nm - So, when red is necessary for bloom is also necessary for growth. In addition, it is found that it is absorbed in plants less well (compared to blue light), then it needs more of it in bloom.

What the future holds for LED lamps and cannabis

What we have now are Beld growth lamps adapted to a complete life cycle; Increases To bloom.

simply, Light from the blue side of the spectrum is consumed mainly at the growth stage - which makes plants strong and healthy with dense foliage. In contrast, The red light is necessary for flowering and reproduction - which creates a rich inflorescence with large, dense flowers along all the splits that were created, in part, as a result of the blue light.

But remember, it is not recommended to use a LED bulb with a single wavelength (for example, all blue or all red) because you need to balance all stages of the plant life cycle.

Find the differences: LED bulb vs. LED bulb
Find the differences: LED bulb vs. LED bulb

Last week, the Royal Academy of Sciences in Stockholm, Sweden, announced that the winners of the Nobel Prize in Physics for 2014 would be three Japanese researchers - for their contribution For research and development of LED technology.

Thanks to Yair Segal for translating this article. source.

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