What Is Light Spectrum?

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The light spectrum is the range of waves within the electromagnetic spectrum that is visible to us as humans. Measured in nanometres (nm), the visible spectrum sits between 380nm to 750nm on the scale. This means the blue end (bottom) of the visible spectrum has a slightly shorter wavelength than the red side (top).

The sun emits solar energy, of which a very small portion ends up reaching Earth. This is because the ozone layer absorbs and reflects back most of the harmful waves, allowing life to thrive. Waves that filter through the ozone layer are between 300nm - 1100nm, so the spectrum entering the atmosphere is wider than we have the ability to see.

Outside of the visible light spectrum we have gamma waves, x rays, ultraviolet waves, infrared, microwaves and radio waves. Ultraviolet waves and infrared waves sit at either end of the visible spectrum meaning they are included in the wavelengths that penetrate the ozone. Both are useful for plants in some ways.

• UVC (180 - 280nm) - Includes harmful ultraviolet waves that are blocked by the ozone layer. Causes serious burns.
• UVB (280 - 315nm) - Can burn skin but only small amounts reach earth. Higher altitude areas will have higher levels of UVB.
• UVA (315 - 400nm) - Always present in the atmosphere but not visible. 95% of ultraviolet waves getting through the ozone are UVA.
• Visible Light (380 - 750nm) - The range of the electromagnetic spectrum that we can see as color.
• Infrared (700 - 1100nm) - Invisible to the human eye but can be felt as heat.

Why Light Spectrum Is Essential

Marijuana plants require the right kind of light to grow to their full capacity. Without the right spectrums of light, plants can underperform, growing small and generating low yields. Luckily, indoor growing methods have allowed us to mimic the most vital elements of the sunlight received by plants outdoors.

Outdoor plants receive the full spectrum of light provided by the sun. In the spring, the spectrum of light that infiltrates the atmosphere results in a bluish color. The blue spectra is what enables plants to produce strong foliage during the early stages of growth.

As the summer arrives, the sun is higher in the sky and more light passes through the atmosphere. By the time fall arrives the sun starts to dip, when the red spectrum is most prominent. Red wavelengths signal the end of summer so plants grow flowers in an effort to pollinate before winter.

How Cannabis Plants React to Light

Cannabis plants can thrive well under blue and red lights provided they receive the right spectra within the color band. By singling out these wavelengths, plants have better access to the kind of light they need. This is one of the reasons why indoor plants can be grown smaller than outdoor plants, because they do not need to expand in search for the required spectra.

• Blue (400 - 500nm) - Blue light is needed for plants to grow strong leaves and branches during its vegetative cycle. Supplying large quantities of blue results in short, bushy plants, which can be useful for growers trying to avoid tall plants with long branches. Suggested for seedlings, especially if you are growing indoors.
• Red/Infrared (620 - 750nm) - Red is important for expanding plant structure and promoting bud production. Naturally, plants utilize red light to identify when it is day or night. Small amounts of infrared make its way through the atmosphere during sunrise and sunset when wavelengths are longer. Marijuana plants grow taller under infrared until visible red becomes more direct.

Photoreceptors in a marijuana plant's leaves are constantly working to comprehend the light spectrum surrounding them. Leaves will turn to face the light during the day. When there is no light cannabis plants preserve their energy by 'relaxing' their leaves, making them sag slightly. Photoreceptors do not really turn light into energy, which is more to do with photosynthesis.

How a cannabis plant reacts to light will also depend on the strain and where it comes from. Some genetics have been brought from high altitude areas where the light is more powerful and there is a higher presence of UVB rays. It has been argued that exposure to more UVB can increase THC production, although this theory is inconclusive and needs to be researched further.

Finest Spectrum to Grow Marijuana

It is tough to say exactly which part of the color spectrum is best but a large part of it relates to the type of light your marijuana plants are grown under. Not all lights give off the same spectrum so choosing will depend on the results you are trying to accomplish. The key is that your garden has enough blue light during the vegetative cycle and sufficient red light for blooming.

You might be planning to grow indoors where you can have full control over the light. Or perhaps you're thinking of trying some outdoor plants, much of which will be determined by the sun. Whichever you choose, make sure your plants receive plenty of light.

• CFL (compact fluorescent light) lights are normally measured in Kelvin (K), which tells us the color temperature of a bulb. Cooler, blueish lights have a higher Kelvin reading (6000 - 6400k), whereas a CFL that looks red will have a lower reading (2800k).
• LED (light emitting diode) - LEDs emit a narrow spectrum of light, either in a small band of blue or red. Red, blue and white LEDs are frequently merged to create a 'full spectrum' emission that plants can comprehend for appropriate growth.
• HPS (high pressure sodium) - Yellow/red light can be used throughout the grow cycle, however plants will grow taller with more spacing between internodes. Marijuana plants benefit from HPS lighting primarily in the flowering stage.

If you are growing outdoors, you can expect plants to get larger than they would indoors since the spectrum is broader. Depending on where you live and the time of year, plants will respond to the light in different ways.

The color spectrum of your grow light is important however if you want to produce good harvests, the intensity is also important. The intensity of your light source plays a significant role in plant growth and has to be powerful enough for plants to photosynthesise correctly. If marijuana plants do not receive enough light, it doesn't matter what spectrum they receive, because they won't be able to function.

For all the grow lighting supplies with the best and latest technology in Kansas City, Missouri, contact Grower’s Choice at 909-972-8419 or visit our website at Growersc.com for more information.