Cannabis growing topics

Understanding Lighting & Cannabis, The Basics

Understanding Lighting & Cannabis, The Basics
  • PAR (Photosynthetically active radiation)
    Photosynthetically active radiation (PAR) is the range of light wavelengths that enables photosynthesis in cannabis and other plants.  This is between 400 and 700 nanometers (NM)
  • Moles (1 mole = 1 million umlos)
    A unit of light measurement.
    • Umlos (Micromoles) (1,000,000 umlos = 1 Mole)
      Umols are the units used to measure PPF.
    • PPF (Photosynthetic Photon Flux)
      Light is photons. This tells us how many light photons the lighting unit emits per second. Basically how intense the output of the light is from the base of the light. These are measured in umols.
    • PPFD (Photosynthetic Photon Flux Density)
      PPFD is used to measure how many actual photons of light your plant is getting. The farther your plant is from the center of your light the less PPFD you will get. These are also measured in umols.
  • DLI (Day Light Integral)
    DLI is the amount of light you give your plant over the time that your lights are on.

Cannabis and most plants like a PAR in the range of 400 to 700 nm. The lower 400’s being best used for the vegetation stage.  While the high 600’s up to 700 nm being better for the flowering phase. The middle of the spectrum is mostly reflected off by cannabis.

Ultraviolet & UV-A

UV-A is found in the 310-400 nm range and is actually harmful to your cannabis plant. But in small amounts it has the benefits of triggering your plants defences making it more resistant to insects.  UV-A has also been known to increase terpenes and CBD/THC potency.

Infrared (IR)

IR is another damaging light spectrum coming in at 730 nm on the lighting spectrum and is needed only in small amounts.  With the right amounts IR can help with bigger yeilds, strong stems and a more well developed plant.

Example of the light spectrum 


When looking at lighting you want to make sure it has a good PAR/PPFD (umols) rating. Good LED lights will have a couple IR and UV-A emitting lights on them.

PPFD rating is very important.  You want to make sure the light you are buying puts out enough umols at the height you want it at.  Look at the manufacturer’s specifications and look at its lighting coverage charts. That will show you how much PPFD you get at different heights and outside the center of the light.
The higher you hang your light the more coverage you will get but the light will be less intense.  Giving off less umols. The closer your light is the more intense it is but has a smaller coverage area.  Also the farther the plant is from the center of the light the less umols you will get.

Also think of

  • The space you are using. Is it a small or hot space?, you may want to go with LED lighting for less heat. 
  • How much electricity can you safely draw?
  • How much cannabis are you trying to yield?
  • What is your budget?

Example of a PAR/PPFD chart

Cannabis is recommended to use between 20 and 40 Moles of light per day. That would be 20 to 40 million micromoles(umols). 1 mole = 1,000,000 umols
If you wanted to give your plant the minimum 20 moles (1million umols) a day in a 12 hour lighting time you would need to give it 463 umols a second of light.

  • For Clones and seedlings
    you can use your normal grow lights if you don’t have T5 or CFL lighting.  But we recommend using a CFL or T5 light for these as you can put the inches away from your clone/seedling and not damage them. Seedlings and clones dont need alot of umols very early on.
  • Vegetative stage
    A range of  310 umols minimum to 616 umols a day maximum
  • Flowering stage
    A range of 465 umols minimum to 920 umols maximum

To Calculate your DLI (Day Light Integral) you need to calculate how many moles a day you want to give your plant.  
you will need to do this:

  • Divide how many moles you want your cannabis to get by how many hours you have your lights on.  Then divide that by minutes in an hour (60).  Then divide that by second in an hour (60). This will give you your PPFD/PAR (umols) rating you will see on the charts.Example during vegetation (18hr lights on) with a target of 30 moles of light a day
  • 30 moles = 30,000,000 umols.  Now take your umol and divide that by your lighting time. 30,000,000 umols divided by 18hrs(18) = 1,666,666 umols. 
  • Now divide that by how many minutes in an hour (60). 1,666,666 umols divided by 60 = 27,777 umols.
  • Then divide that by how many seconds in a minute (60). 27,777 umols divided by 60 = 462 umolsExample in Short form
  • 30,000,000/18/60/60 = 462

That sums up the very basics of choosing lighting for cannabis. There is a ton more research and information on this subject we will bring you later.  Always remember to research and ask questions if you are ever unsure of something. The Happy Buddha & cannabis community love to help!

One thought on “Understanding Lighting & Cannabis, The Basics

  1. edward september says:

    Wanna buy one of these growing pots

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