How to Develop Autoflowers in the Best Light Spectrum

How to Develop Autoflowers in the Best Light Spectrum

How to Develop Autoflowers in the Best Light Spectrum

Providing different spectrum at different stages of the process can have an impact on the consistency of your crop.

When growing auto-flowering plants indoors, it’s important to mimic their natural environment. Humidity, temperature, and, most importantly, light are all parts of the atmosphere.

For growing plants indoors, the strongest grow lights for autoflowering spectrum is one that is as similar to the spectrum of the sun as possible or a complete spectrum.

Whether you use light bulbs or LED’s, the right spectrum of light is required at each stage for optimal development.

1. What exactly is the Light Spectrum?

The light spectrum refers to various colors (or wavelengths) that a light source can produce. Nano-meters (nm) are the units of measurement for light, and each nanometer reflects a band of light (a band of light is a section in the color spectrum). Humans can only see a small portion of the spectrum, reaching from 380 to 780 nano-meters, which means we can only see violet to red colors.

The sun, including its white appearance, is a full spectrum light source that comprises all spectral wavelengths. Rainbows appear as a result of this. You can see all the colors (visible to humans) that make up the sunshine as raindrops refract light into individual wavelengths.

Visible Spectrum [380nm-780nm]

Cannabis plants flourish in the sun and absorb the entire spectrum of wavelengths. This means that in order for our cannabis plant to thrive, we must have as much wavelength as possible.

Although it is not needed, providing the best light spectrum to stimulate plant growth is recommended.

Remember that this is not a rule; you will cultivate your cannabis plant from seed to harvest using any light spectrum or amount of light, but this would have a significant impact on your yield.

2. Each Stage’s Light Spectrum

The best range of light for rising plants.

Cannabis in the wild requires blue wavelengths to develop high, tall, and encourage leaf growth during the vegetative stage. We want to grow as many leaves as possible while growing indoors. Through more leaves, there is more surface area available to capture light, ensuring that our plant grows a solid stem and branches in preparation for flowering.

The best spectrum of light for blooming plants.

Cannabis in the wild uses red wavelengths to encourage bud formation as it enters the flowering stage. We need to give the plant red wavelengths if we want to grow thick buds and improve yields. This would increase the rate of photosynthesis, which will increase bud development.

Use “red” light when playing with training to help plants grow taller, making it easier to practice.

The general theory is that “blue” light produces shorter and stronger plants with more leaves, while “red” light produces taller and weaker plants with fewer leaves (when opposed to plants grown under “blue” lights).

3. Different types of light bulbs and LED’s are the two most popular types of cannabis grow lamps.

Light bulbs have a small wavelength range, which means they don’t emit any of the colors in the light spectrum, making them narrow-spectrum lamps.

LEDs are full-spectrum lights, and they emit nearly all the colors in the spectrum. They are made up of blue, red, and white diodes, allowing them to emit all the wavelengths in the spectrum.

Light Bulbs vs. LED’s

LED’s vs Bulbs

  • Expensive                 Cheap
  • More efficient            Consume more electricity
  • Take less space        Need more space
  • Runs cooler               Emit a lot of heat

HPS, MH, CFL, and HID light bulbs are available.

  • Metal Halide (CMH),
  • High-Pressure Sodium (HPS), 
  • Compact Fluorescent Lights (CFL),
  • High-intensity Discharge (HID)

Mentioned above are the four types of light bulbs available (HID).

Since they emit a “gray” glow, MH lamps, which have a Kelvin rating of about 6500, are often used for cannabis in the vegetative stage (aka colder light).

HPS lamps, which have a Kelvin rating of 2000, are often used for cannabis in the flowering stage because of their “red” glow (aka warmer light).

CFLs are measured at about 5000 Kelvin and emit a very faint “gray” light. They can only be used for cannabis seedlings and clones for the first few days since they only need to produce roots. Once the vegetative stage starts, they should be moved to a growing space with better lighting.

They are similar to HPS but contain xenon inside, emitting a different light spectrum and are more effective despite being more lightweight. HID can cover a temperature range of 3500 to 5000 Kelvin.

Tip: You should cultivate your plants with both CMH and HPS bulbs, which is known as a mixed light spectrum and will yield a stronger crop.


  • LED lamps are less expensive than standard LED lights.
  • You don’t have to install the whole fixture; just replace the lamp.

Negative aspects:

  • As compared to LED’s, the cost of electricity is higher.
  • Additional cooling equipment is needed.
  • Before approaching the flowering stage, bulbs must be changed (CMH to HPS).

Infrared and UV lights, as well as full spectrum LED’s

Unless otherwise specified, all LED’s are full-spectrum lights; they do not include all wavelengths but will emit the appropriate amount for each level of cannabis plant development. Unlike light bulbs, you won’t need to adjust anything except your timer while you’re approaching flowering.

If full-spectrum LEDs with UV and infrared diodes are not available, LEDs optimised to emit such spectrum are available. They aren’t widely used in cannabis indoor cultivation, but they are said to be beneficial to farmers.

Cannabis plants, like all else on the planet, are harmed by so much UV light, but just in the right quantity. It may encourage the development of trichomes, which cannabis plants grow to shield themselves from too much sun.

Infrared lights, like UV lights, can damage the plants if used in excess, but when used in moderation, they can enhance photosynthesis, improve yields, plant growth, and plant health.


  • Used in the life cycle.
  • It is energy-efficient.
  • Lasts longer than candles.


  • The price is higher.

Note: Having UV and Infrared lights is unusual; they’re costly and aren’t needed for good flower growth. They’re best suited to more seasoned growers who choose to try out new spectrum.

4. The Best Auto-flower Spectrum of Light

As most of you are aware, cannabis plants have two stages: vegetative and flowering, both of which necessitate a distinct light schedule and a spectrum.

Autoflowers, unlike photoperiodic cannabis plants, spontaneously reach the flowering stage and depend solely on the age to begin growing buds.

As a result, it’s important to carefully choose the cannabis light spectrum; we consider using a combined light spectrum with warm and cold light bulbs (CMH and HPS) or a full-spectrum LED during your auto-flowering entire lifecycle.

This ensures that the plant receives a full range of light, resulting in the best flowers and highest yield.

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