pH and PPM: Knowing What Your Plants Are Eating and How Much They Can Handle

pH and PPM: Knowing What Your Plants Are Eating and How Much They Can Handle

Your Ph and PPM help you to know what your plants are eating and how much they can handle in terms of additional nutrients.  If your Ph or PPM is off, your plants are going to experience nutrient lockout.  This occurs when your plants are unable to absorb the nutrients they need because your water is too acidic or possesses too much alkaline.



When people refer to your pH level, they are talking about the acidity of your water.  pH is measured by analyzing the amount of hydrogen in your water.  Once this data is gathered it is then put into a mathematical equation.


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This equation will produce a number that can be categorized into one of these sectors below.  Take notice that there is a large jump between the values of each pH.  This means being off just one point of one number on your pH can make a huge difference.


Pure water has a pH of 7 and is considered neutral.  Depending on your growing medium, you will have to drop this pH level down to allow your plants access to all of the nutrients in your feed. 



If you are growing in soil, a pH between 6.0 - 6.5 is going to work best.  This is the range that your plant's nutrients are water-soluble, so you will want to maintain this level.  In a hydroponics setup, you will need to adjust your pH further down to around 5.5.


The only way to test your pH is by using meters or test papers, the latter being less reliable.  A good pH meter can help you to dial in the perfect settings to give your plants the optimal growing environment.




Your Parts Per Million or PPM reading is very important in helping you to determine what nutrients your plants need most.  Your PPMs tell you what the particle density is in your feeding solution and helps you to avoid over or under feeding.  Your PPM reading does not account for the fact that some particles are harmful and as result of this, you will usually have to readjust your pH after getting your PPMs on target.  This process can take a little getting used to but once you have your mixture correct; you will be able to dial into your specific needs with ease.  Below are the ideal PPM readings for Cannabis.



100 - 200

Early Veg Cycle

300 - 400

Late Veg Cycle

450 - 700

Early Flowering Cycle

750 - 950

Late Flowering Cycle

1000 - 16000


To help ensure your PPM meter isn't getting inaccurate results you will want to use some sort of filtration to clean your water.  A triple osmosis filter can be a great option to consider but you should be aware that this type of filtration could also remove some helpful nutrients such as calcium and magnesium.  You will want to re-add these nutrients into your water prior to feeding.  Cal-Mag is a popular product used to correct this problem.


Use your PPM meter first to set up your feeding supply and then next use it on the water after it has passed by the roots.  You will notice a dramatic reduction in your PPM's.  This can tell you how much nutrients your plants are absorbing at that time, so you can determine the best possible feeding solution.

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  • David Hamilton
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