pH and Cannabis Plants: What you need to know

How Does pH Affect My Cannabis Plants?

pH levels that are out of balance can cause the growth of your plants to suffer, resulting in a lower yielding crop. But don’t worry, if you monitor your plants pH levels and address any readings of concern you can take action to put the pH levels back in balance, and grow a healthy successful crop.

What Items Do I Need To Measure and Adjust the pH of my Cannabis Plants?

How Do I Measure the pH of My Nutrients?

Step 1: Mix up your nutrients and water

Step 2: Use the pH Pen to test the solution. Make sure to keep the pen in the solution for 1 – 2 minutes for the reading to stabilize.

***Note: It is a good idea to keep a pH Test Indicator on hand incase you encounter trouble with your pH Pen, such as dead batteries. In a pinch the pH Test Indicator can be used to measure pH levels. To use just add a sample of your nutrient / water to the tube provided and add a few drops of the solution. Next match the colour of your water to the corresponding list on the box to determine if any pH adjustments need to be made. This method is less accurate than using a pH Pen, but will be helpful in an emergency.

How Do I Adjust the pH of My Nutrient Solution?

Step 1: Based on your reading, decide if you need to add either pH up or pH down to the solution, to achieve your desired pH level (Usually between 5.8 – 6.3 is ideal)

Step 2: When adding pH Up or pH down, start off slow until you know the amount you need. Different brands of pH Up or pH Down have varying levels of strength, and the size of your reservoir also matters. Always be very cautious when adding pH Up or pH Down to your water and start with just a drop or two, until you determine the amount that is right for you and your nutrient mixture. It is recommended that you begin with a brand that has a weaker formula. A guideline for the strength levels of different brands is provided below:

BrandStrength Level
Advanced NutrientspH Up and pH DownStrong
Green PlanetpH Up and pH DownStrong
General HydroponicspH Up Liquid and pH Down LiquidWeak
Bumper CroppH Up and pH DownWeak
TechnaflorapH Up and pH Down Weak

***Ensure you stir thoroughly when adding the pH up or pH down to your solution.

Is There Organic pH Up and pH Down?

Yes, there are options for organic pH adjustments. While it is nice that they are natural, they do have their own drawbacks. The main issue when using organic pH adjusters is that they do not hold the pH for very long, so more frequent testing and adjustments are required. If you are looking for an organic option try Earth Juice Natural pH up and down.

Calibrating Your pH Pen

You will need to calibrate your pen at least once per month. To do this, add some pH 7 solution to a 250 ml cup. Put your pH Pen into the solution. If your Pen is calibrated you should get a reading of 7. To ensure you are properly calibrated you may repeat the above using the pH 4 Solution, achieving a reading of 4.

A reading that is 0.2 out is acceptable (for example you are using pH 7 and get a reading of 7.2)

Be careful not to cross contaminate your cup or pen when switching from calibrating with the pH 7 and pH 4. It is important to properly clean the cup and rinse the pen well in between using the pH 7 and pH 4 solutions.

Storing Your pH Pen

As well as calibrating your pH Pen, proper storage is important. To properly store until your next use, add 1 – 2 ml of Storage Solution into the cap and close.


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