LED Grow Light Spectrum Explained

So you’re in the market for a Grow Light huh? maybe you’re an seasoned grower who’s always stuck by the tried and true HPS lighting systems and although you’re interested in LED technology ( and so you should be! ) you’ve heard through the grapevine of their shortfalls and high pricing and with all the conflicting information out there making it hard to decided which you to go for, leaves you more skeptical than excited? or maybe you’re just new to growing and want to make sure you’re starting out with best practices and ensuring your Grow Light system will actually do the trick and grow your plants to resemble mini skyscrapers.

Well, regardless of all that this article is simply to introduce you to the world of LED Grow Lights and hopefully shed some light on the light spectrum's and what the hell they actually mean, how to read them and what your plants actually care about.

An Introduction to the Color Spectrum


When we talk about the colour spectrum, we are referring to the chart below it is basically a way to measure what you see when you shoot sunlight through a prism.

The chart below is displaying the spectrum for our new upcoming 4Seasons XP35 Gen 7 COB @ 3500k cct.


This is the range of wavelengths that our light source produces as you can see at the bottom of the chart. As humans, our vision is limited within this range as we can’t actually see Ultraviolet and Infrared or more specifically what we see is within the range of 380nm to 740nm. 

With that being said obviously what you’re after is how this will influence your plants  and not yourself, however, it is interesting none the less!

Plants pick up on a lot more than we can including ultraviolet such as 260nm - 380nm PAR range  400 - 700nm  and Far-Red  700 - 850nm. You have to remember that as we are looking for an LED Grow Light to use as a sole lighting source, meaning we won’t be able to use anything else, we need to make sure the spectrum is suitable.

An Insight Into The Grow Light Spectrum

Light spectrum refers to the range of wavelengths that can be produced by a certain light source.

Light refers to the visible wavelengths of the electromagnetic spectrum that humans can see, and this ranges from 380 to 740 nanometers this is also known as the PAR range ( Photosynthetic Active Radiation )

The Way Plants Respond to Light

Plants, in every case, use light for their photosynthesis and photomorphogenesis process.

Photosynthesis is the way organisms convert light energy into chemical energy.

Photomorphogenesis is the way plants modify their growth in response to the light spectrum that they are receiving.

Remember that light affects a plant's development stage such as flowering.

It is important to note that plants' use of photosynthesis ranges from 400 to 700 nanometers, while photomorphogenesis happens at around 260 to 780 nanometers. 

The Importance of the Light Spectrum During the Growth Process of Crops

All plants feature photoreceptors that can be triggered through different growth characteristics.

These are commonly activated through photons of specific wavelengths. 

Controlling the light spectrum can affect the way a plant grows.

Some important characteristics that are affected include flowering yield, rate of growth, fruiting, root development, compactness, nutrition, flavor, color and plant health.

Keep in mind that actuating a plant response while using a certain light spectrum is only a single component of a much larger process and the result can differ tremendously depending on the different factors such as the growth environment, plant species and the light intensity itself.

This concludes part 1 of this 2 part article, working through the New Zealand lock down has been absolutely mental so I will aim to finish Part 2 in the coming week.