We recently received a query from one of our green thumbed readers in regards to what PPM (parts-per million) levels are considered ideal for each growth stage of cannabis.

So, we thought we would not only list the idyllic levels for each phase of a cannabis plant’s life, but also do our best to define parts-per million (PPM) and the role it plays in cannabis cultivation.

What is PPM?

Technically speaking, the parts-per notation is a set of imitation elements commonly used in the fields of science and engineering in order to illustrate diminutive values of various dimensionless quantities. A dimensionless quantity is a quantity to which no physical dimension is applicable. In addition, parts-per million is used as a way to calculate minute levels of pollutants in air, water, plant water runoff, etc.. From a mathematical standpoint, parts-per million is the mass ratio between the pollutant component and the solution, and PPM is defined as:

PPM = 1,000,000 mc / ms         (1)


mc = mass of component (kg, lbm)

ms = mass of solution (kg, lbm)

PPM can be also be expressed as:

  • 1 PPM = 0.0001 %
  • 1, 000 PPM = 0.1 %
  • 10, 000 PPM = 1%


Say what?

I know, right?

In layman’s terms, PPM is a way of expressing very dilute concentrations of substances. For example, per cent means out of a hundred, therefore parts-per million or PPM means out of a million. The notation more often than not describes the concentration of something in water or soil. One PPM is equivalent to 1 milligram of something per liter of water (mg/l) or 1 milligram of something per kilogram soil (mg/kg).

What role does PPM play in cannabis cultivation?

First of all, one must possess a meter designed to gauge PPM in order to determine what their particular level of particulates indeed are. Once you’ve obtained said meter, it’s then used to not only help measure the levels of nutrient and/or fertilizer solution you’re using per gallon of water, but it’s also used to determine what rate of particles are present in the water you’re using to feed your crop.

Before deciding the amount of nutrient solution you’re going to mix per gallon of water, it’s best to measure the PPM level of your water supply in advance in order to determine the proper ratio of nutrient solution per gallon of water you’re going to use. For example, let’s say you want your solution mixed with water to be at approximately 850 PPM. So, if your water is testing at 120 PPM you would need to have a nutrient solution level of around 730 PPM in order to reach your desired reading.

Although knowing the exact levels of PPM can be instrumental when attempting to determine how much nutrients/fertilizers to feed your cannabis crop (especially for those using a hydroponic gardening system), it’s suggested to let the plant(s) tell you how much nutrients/fertilizers it needs.

Not all strains of cannabis require the same PPMs. So, rather than attempting to use a PPM meter to establish the amount of nutrients/fertilizers you’re feeding your ladies, use the meter to keep track of your milliliters to gallons ratio in order to dial in your feeding schedule. It’s highly recommended that you start by feeding your crop a weak nutrient/fertilizer per gallon of water ratio and continue to slowly increase the amount as your plant(s) begins to show you their dietetic requirements.

PPM levels chart:

  • Seedlings, Early Sprouts – 100 to 250
  • Early Veg’ Stage – 300 to 400
  • Full Vegetation Stage – 450 to 700
  • Early Blooming Stage – 750 to 950
  • Full Mature Bloom/Ripening Stage – 1000 to 1600

Do you have question concerning cannabis cultivation or anything related to weed?

Then drop us a line anytime at erik@the420times.com 😉

Grow on and keep it green!

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