Grow Lighting PAR, What Does PAR Mean

Cannabis grow light technology is always changing. Grow lighting PAR, is something that growers have never really had to pay attention to before.

Now there is so much choice, and hundreds of different models of LED lighting, you have to know more about lighting to make sure you’re not being ripped off.

In this guide, we will go through what Grow Lighting PAR is, what it means, and how it affects plant growth. It may get a bit complicated, but as usual, this guide will be broken down to make it as simple to understand as possible.

There is one sentence that is going to make this whole guide a whole lot easier to understand:

Lumens are for humans, PAR is for plants.

What is PAR

Lighting intensity is measured in lumens. One lumen is equal to the light given off by, 1 birthday cake candle, 1ft away.

what lumens means, 600 lumens is equal to 600 candles,

For example:

A bulb emitting 600 Lumens, is as bright as 600 candles, one foot away.

Lumens will tell you how bright a light is, but, plants will not use light the same way our eyes do. They will only use different colours of light, to do different things. This is where PAR comes in.

PAR stands for ” Photosynthetic Active Radiation “. This is light that is used by a plant, for photosynthesis.

You see, a plant makes sugars and starches for energy out of light. When a photon ( a small packet of light) hits a leaf, it will excite certain molecules. The energy provided by this photon, helps water ( H²0) and carbon dioxide (CO²) react together to give the plant carbohydrates.

A plant will use the carbohydrates to process nutrients, and grow bigger and stronger. The more light you can provide to the plant the better, but it should be the right kind of light.

Plants can be grown under any colour of light. Red, Blue, Yellow, they will grow, but they will not flourish the way you want them too. A plant needs a good mixture of different spectrums of light.

This is why it is important to get a light, thats has a range of colours in it. For example, you may see a blue light, that has a ridiculously high amount of lumens. It may be very bright, but your plant needs more than just blue light to grow properly.

Light Spectrums for Cannabis Plants

light spectrums and PAR, Par Grow Lighting

There is a range of light called visible light. This is the spectrum of light that can be seen by humans. It is white light, that consists of all of the colours of the rainbow.

When you head out of the visible light spectrum, you start to get to the infra red, or on the other end, the ultraviolet. Some grow lights now add these spectrums into their models.

Light will change colour, depending on the wavelength. The bigger the gap is between each wave of light, the more red that light will be. Also, the closer together the waves are, the more blue the light will be.

The gaps between these waves are so small, they are measured in centimetres, nor millimeters. The gaps in between waves of light are measured in “nanometers”


This can get complex, but it is essentially, the size of gap between the peaks or troughs of two waves.

PAR, nanometers light charts,

Blue light has a smaller wavelength in nanometers (400 nm), which means the waves are close together. Alternatively, red light has a bigger wavelength (700 nm), this means the waves are further apart.

Outside of the visible light spectrum you have UV ( Ultra Violet), X Rays and Gamma Rays. On the other end, there is Infrared, Microwaves, and Radio waves.

They all make up part of the light spectrum, a small part of it can be seen by humans, and a small part of it can be used by plants. Finding a light that is designed to deliver not only bright light, but the right light to your plants, is key to growing the best plants.

LED grow lighting is very efficient, and gives your plants the exact light they need. You just have to make sure you buy one that has the right PAR.

How to Tell if a Light Has Good PAR

how plants use light spectrums, Grow lighting PAR

When you first look at a new grow light, you will need to look at two things:

1: The light intensity, this is how bright a light is and how many photons are produced by it.

2: The Quality of the Light. For example how much red, blue, green, yellow, and different combinations of light it emits. Some grow light will only emit a thin part of the spectrum, usually blue mixed with red, and this isn’t good enough for growing healthy plants.

Most grow light will emit light that are in the visible light spectrum. This is light between 400nm and 700nm, that can be seen by the human eye. But, some grow light will go into the Infrared or Ultraviolet.

Each colour, has a different wavelength in nanometers, with the lowest wavelength being in the blue spectrum, and the highest being in the red. As you can see in the picture above, Indigo, is between 430 and 450 nanometers, but red ranges from 650-700 nm.

The most important wavelengths of light for a plant, are between 400, and 700 nm, this is what PAR is, photosynthetically active radiation. .

It is important to note that in this PAR range, there is green light. Many growers will suggest that a cannabis plant doesn’t use green light, but there is plenty of evidence to suggest differently.

Growers for decades have used blue lighting for vegetative growth, and red lighting for flowering. But it is now suggested that full spectrum lights may the best lighting for your plants.

There is also plenty of evidence to suggest that ultraviolet light, and far red, have some effect on plant growth too. So though we may not see the light, the plant may find it useful.

What Spectrum of Light is Best for Plant Growth

Photosynthetic absorption rate, grow lighting par,

You may have seen charts like this whilst looking for new grow lights. This chart shows how much light of a certain wavelength, different types of chlorophyll absorb.

Plants seem to absorb light best in the blue, and red spectrums. But looks to be very low in the green and yellow wavelength. Because of this, growers for decades have grown plant in veg under blue lighting, and plants in flower under red lighting.

But recent studies suggest, that this is wrong, and a plant actually absorbs much more green than initially thought. Though a plant reflects a lot of green light, it also uses a substantial amount if it too. Removing it from the spectrum all together, can be detrimental to the plants growth.

Research suggest, that rather than giving your plant more of a certain spectrum of light, a full spectrum light can give the plants the light energy it needs in all different wavelengths. So to give the plant a good mix alot across the 400-700 nm spectrum (PAR) will be best.

Even adding some supplement light for extra deep red, or blue will help the plant grow. The more a grow light can imitate sunlight, the better, as this is the light plants have evolved with for millions of years. They know how to use it.

How to Choose the Right Light By its PAR

When you are looking to buy a new grow light, or bulb, grow lighting PAR is an important factor. You can find out what PAR a light covers, usually from a graph on the side of the box.

The graph, or chart, will look similar to these:

mh light spectrum graph

Metal Halides. Blue spectrum lighting, that will give a spectrum similar to this chart.
You can see it has more blues and greens, but very little red.

hps light spectrum graph

High Pressure Sodium. Used for flowering plants, and is heavily in the red spectrum.
As you can see the is very little blue.

Before you buy a light, look for a graph like this somewhere on its box, or on the manufacturer’s website.

Look for a light that give of the most amount of light in the right spectrums, this should be between 400 and 700 nm.

White light, or full spectrum light will give the plant all of the light is needs to do whatever it needs to do. This is what you should be looking for when buy LED lighting and HID lighting too.

How LED Lighting and PAR Works.

Most LED Lights, will consist of number “Diodes” that emit a particular wavelength of light. Sometimes this can be 3, 4, 5 or a full range of colours.

For example, you may have heard of “3 Band LEDs”. This means, the light emitted from this LED, will come from diodes consisting of three different colours, or wavelengths.

The best LEDs use some diodes that are coated in Phospur. Blue light is emitted from the diode, then pushed through the layer of phosphor. It is then converted into a more white, yellow light.

This is an expensive process, and can make a difference in the price of your lighting. But, it is worth it to get the right light.

LEDs can come cheap, but they wont give your plant what it needs. Buying high quality LED lighting will not only be better for your plants, but will also reduce your energy costs.

Best LED Grow Lighting PAR

The most recent upgrades to LED lighting are from Samsung. They build diodes that emit different wavelengths of light, and cover a great range of PAR.

Samsung LED PAR chart, grow lighting PAR

Samsung insists different perspectives that various wavelengths are actually important for entire plant growth. This has been supported by numerous internal and external experimental studies.

Following its extensive research into the matter, Samsung has determined that a broad white spectrum with selected red spectrum yields better results and allows lower overall costs, in general. Samsung’s broad spectrum of white LED including blue, green, yellow and specific wavelengths of red LED (660nm and 730nm) can provide optimal lighting to make plants grow better.

This is an example of the spectrum of light produce by their diodes. As you can see, it not only provides the plant with light from the whole visible light spectrum, but it also peaks in the red and blues.

Invisible Sun LED grow Lighting uses these Samsung Diodes in their boards. They also offer have red supplement lighting that can be added to their models.

Grow lights from Invisible Sun, use a variety of different diodes from Samsung, to give the best Grow Lighting PAR for growing cannabis plants.

Grow Lighting PAR Conclusion….

PAR is simply, the wavelength of visible light that plant will absorb to photosynthesis. This is between the wavelength of 400-700 nm.

Look for white light, that gives a range of colours across PAR, rather than a light with a selection of a few wavelengths.

Invisible Sun are a sponsor of our site, and we don’t want you to think we recommend them just because they are sponsors. They make quality lights, and have done the research. They are sponsors of our site, because we think they are the best.

If you want the best lights, with the best PAR, then you should consider Invisible Sun Lighting. You can get a ten percent discount code on any light by using our discount code in our cannabis growers forum.

Thanks for reading Percy Growers, happy growing.

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