Hello everyone!

 

Welcome to Platinum LED’ s new blog where we plan on discussing a variety of key topics on grow lighting, grow tips, and general industry information.  For our first entry we will discuss white light LEDs and how they can be used most effectively for growing plants.

 

Is the spectrum of light generated by white LEDs ideal for growing?  This is not a simple yes or no answer!  Let’s take a moment and look at the science behind it without all the all the hype.

 

White light is a combination of lights of different wavelengths in the electromagnetic spectrum. White light can differ based on the specific Correlated Color Temperature (CCT) of light that is being produced.  Here is an image CCT chart in Kelvin that shows what type of light is produced at different Kelvin temperatures:

The lower the Kelvin temperature the more red or infra-red light is produced. The higher the Kelvin temperature the more blue light or UV light is produced.  Depending on the light source and color temperature of the light different types of whites are available.  An example of this is the CREE XM-L2 LED chip that is available in three full spectrum white varieties:  Warm White 2700-3750K, Neutral White 3750-5000K, and Cool White 5000-8300K.  The color temperature of daylight can vary depending on time of day, part of year and cloudiness.  5200-6000K is the color temperature used mostly in photography and film for true white light (sunlight at noon).

 

Photosynthesis is the basis for plant development and uses multiple pigments within a plant to absorb light.  Green Chlorophyll A and B are the most prominent pigments within a plant and mostly collect blue (400-500nm) and red light (600-700nm) for energy. Green light (510-580nm) is mostly reflected back and has weak light absorption by chlorophyll and little morphogenetic effect.

 

But that doesn’t mean that green light isn’t used in plant development!  Accessory pigments such as Carotene and Xanthophyll, aid in the photosynthetic process, and do absorb certain levels of green light, just not in great quantities.

 

Absorption Vs.  Action Spectrum

 

Action spectrum for Cannabis sativa L.

 

There is quite a bit of debate about the Action spectrum and Absorption spectrum when it comes to cannabis development. The Action spectrum is the range of wavelengths of light that are used in the light dependent reactions within plants.   The Absorption spectrum is the range of wavelengths of light that are absorbed by green chlorophyll and other chloroplast pigments.   The Action spectrum leads us to believe that cannabis plants need more white light, which includes a combination of all the different light wavelengths, but that is not the case.  Plants do need green light (510 to 580nm) for different pigments used in photosynthesis, just not in high intensities or in all stages of plant development.

Absorption spectrum for chloroplast pigments

 

Cannabis clones and seedlings need less intense light and grow much better under the Action spectrum, which is a whiter light.  In fact, intense blue or red light is potentially harmful to the plant at this stage of development.   Once cannabis plants move into the vegetative stage, they require less white light found in the Action spectrum and more blue focused light for photosynthetic response.  Likewise when cannabis plants move into the flowering stage they need more focused red light for photosynthetic response. You can see the focused blue (400-500nm) and red light (600-700nm) both peak in the Absorption spectrum. In short, baby plants (clones & seedlings) love Action spectrum, while adolescent and adult plants (vegetative and flowering stages) love the Absorption spectrum.

 

 

White LEDs & COBs

There are two types of LED technologies that produce white light that generally used to grow plants, white LEDs and COB (Chips on Board).  White LEDs can be found in a variety of different CCT ranges and a most commonly produced by using a blue LED with a phosphor coating that emits yellow light.  The blue light emitted from the blue LED hits the phosphor coating, which releases some yellow light. The yellow light mixed in with residual blue light that has not been absorbed by the phosphor makes a shade of white light.

 

Another way less common way in which white LED’s are produced is by combining 3 colored LED’s into one diode, normally red, green and blue (RGB), producing the white light.

 

Platinum LED uses the CREE XM-L2 warm white light (2700-3750K) diode for supplemental light in the XML2 series of panels.  The XM-L2 diodes can be turned on separately with the BOOST switch for supplemental white (full spectrum) light.  As mentioned above clones and seedling grow most effectively under the Action spectrum which contains more full spectrum white light.  We recommend using only the BOOST switch for that stage of plant development.  The BOOST switch can be used with the VEG and/or BLOOM switch for extra intensity during the vegetative or flowering stages of plant development.

 

Platinum LEDs (P-Series and the XML2-Series) all use a 12 band spectrum of light.  Each diode has a specific nm range where is focuses the most intensity, but also has bleed-over 20 to 30nm on each side of the wavelength.  Our P-Series lights offer a full spectrum of light because of the 12 bands and their proximity to one another with the bleed-over effect.

 

Finally, COB (Chip on Board) is a new LED technology that is used to produce full spectrum white light.  COBs are produced by packaging multiple diodes together on one chip, with a yellow phosphor coating making an intense white light.  Here is an example of a popular COB grow light color spectrum:

5COB chips can produce a great amount of PAR, but also waste a tremendous amount on energy in the green spectrum (510-580nm) range, as you can see in the image above.

 

While COB and white light LEDs can grow plants, with all of the energy wasted in the green spectrum they aren’t necessarily the most efficient.  White LEDs only produce 40% of usable light and the rest is wasted in power consumption and heat.  Platinum LED believes mixing LED diodes that target the nanometer (nm) ranges plants love, is the most effective and efficient way to grow plants.  White LED’s and/or COB can be effective if they are used sparingly as supplemental lighting within an LED panel or specifically for seedling and clone development.

Summary:  While white LEDs can provide good response and growing power in very young/immature plants, the most efficient, powerful way to fully grow plants is to tailor the spectral output of an LED grow light to the Absorption spectrum by use of narrow banded LEDs in a perfected balance.  White LEDs by nature are and inefficient and wasteful when used as the primary source of light in an LED grow light.  This inefficiency goes against the very core principle of the concept of LED grow lights which is producing 100% usable light by way of a perfected spectral output as it pertains to the rate of spectral absorption by green chlorophyll.  Not only has scientific research shown this, but actual results of growers worldwide have proven this time and again.  Not only this, but due to the very nature of how “white” LEDs are actually a phosphor coated blue LED, they will never reach the same intensity level as a quality narrow banded LED.  When you filter light, you lessen it’s intensity.  Since intensity spectral output are what actually grow plants, these are not only the most important factors in an LED grow light’s power, they’re the only factors with regards to growing power.