A ‘full spectrum’ grow light is a light source suitable for growing plants through it’s full life cycle from seed to harvest. As lighting technology has advanced it has become possible to tailor the light recipe for plants. The mixing of this recipe comes in many forms and we are looking at the three main options for small to medium sized home growers:
Fluorescent Tubes (T5) and Compact Fluorescent Lights (CFL)
In order to achieve a full spectrum of light the fluorescent grow light manufacturers mix tubes of two colours; a cool white (6800K colour temp) and a warm white (2700K colour temp). With a standard fluorescent tube, like a T5, they mix the tubes in the fitting.
The development of the compact fluorescent allowed larger power units to fit smaller spaces. The coiling of the tube allows a long tube into a small space. Dual spectrum CFL’s use a warm white (2700K) and a cool white (6800K) tube in the same fixture and mix the light together. The spectrum it produces is a mix of blue, green and red light close to the spectrum mix of the sun.
Red/Blue(Burple) LED panels
In the early days most LED grow lights used many small Red and Blue LED’s (Single Mounted Devices, SMD’s) mounted on panels and usually in fan cooled boxes.
These low power red and blue LEDs were the only efficiency sources available at the time. They are still being used and the spectrum output will vary depending on the colours and mix of LEDs chosen for the grow light. Usually they are limited to using Red and Blue LEDs but some of them include white LEDs or Infra Red or Ultra Violet LEDs also.
COB (Chip On Board) LED grow lights
The yellow surface of the COB LED is a phosphor coating over many small blue LED’s packed together. The phosphor coating converts the blue light into white light with all the wavelengths of colour from deep blue to far red.
The other major advantage of COB LED’s is their efficiency. High efficiency COB LED grow lights are 50% more efficient than Red/Blue panel LED’s and 300% more efficient than Fluorescent tubes.
Overall comparison of the ‘Full Spectrum’ grow lights
The simplest way to compare the spectrum outputs of the grow lights is to show their Blue, Green and Red light content in percentages and compare them to the suns output.
You can see that the Red/Blue LED panel grow lights like the UFO do not contain a similar light output to the sun. They lack the green light which is great for canopy penetration and healthy growth.
The dual spectrum fluorescent lights have a good mix of Blue, Green and Red light but they are now far surpassed in efficiency terms with LED’s being at least twice as efficient and, in the case of COB technology, three times as efficient. They are cheap to buy but, due to low efficiency, very expensive to run.
The COB LEDs produce a full spectrum light with all of the wavelengths of colour from Blue to Red for full and healthy growth. The best aspect of COB LED’s is that they are among the most efficient lighting sources available today.