The Importance of pH Levels When Growing Cannabis

Let me teach you about the importance of pH levels when growing cannabis plants. The pH levels of your soil can make or break your grow. You can technically grow plants without pH balancing your water. But, it is highly recommended as pH levels are directly connected to nutrient absorption. It is a good idea to create slight variations (0.1-0.2) in your waters pH levels within the range as different nutrients absorb at different levels of pH. By ensuring the correct pH range is given to your plants, you can rest assured that you’ve reduced your chances for nutrient lockout and nutrient deficiencies. Your ideal pH range also depends on your growing medium.

Ideal pH Levels for Your Plants:

  • Soil/Compost – 6.0 – 7.0
  • Coco coir/Soilless medium – 5.5 – 6.5
  • Hydroponics/DWC – 5.5 – 6.5

Testing Your Waters pH Level

There are a couple different ways to test the pH level of your water.

  • Digital pH pen
  • pH testing kits with drops/test strips

Digital pH Pen

Digital pH pens are relatively cheap and easy to find online or at your local hydroponic store. They also require you to purchase calibration fluid. You need to regularly calibrate the pH pen to ensure it’s accuracy. You do this by adding the calibration fluid to a cup of distilled water and then you adjust it with a small screwdriver until it reads the correct reading. It is the more expensive option but offers a more accurate reading.

To test your water using the digital pH pen:

  • Gently shake or stir your water
  • Add some water to a small glass
  • Place digital pH pen into glass of water and let it sit until the reading stops fluctuating; this final number is your pH reading

Test Strips/Drops

Test strips or pH testing drops are a cheaper alternative that offer a slightly less accurate reading. The test strips and drops both have different colours that they change depending on the pH level. But, unlike the pen which gives you an exact reading (ex. 6.3). The test strips and drops give a colour with a reading (ex. Light green 7.0, Dark green 8.0) and any in colour variations in between are up for interpretation. You make a estimation based on the colour.

To test your water using the test strips:

  • Gently shake or stir your water
  • Add water to a small glass or testing container if provided
  • Place test strip in water for the suggested length of time
  • Compare colour to the scale given

To test pH using the drops:

  • Gently shake or stir your water
  • Add some water to the testing container provided
  • Add 3-5 drops of pH testing liquid to the water sample
  • Close testing container and gently shake to mix
  • Compare colour to the scale given

pH Up & Down

Both methods of testing pH levels may require you to use a pH up or pH down. There are store bought pH up & down solutions but you can also use lemon juice as a pH down for an all natural option. A little goes a long way for lemon juice so be careful and add very little at a time. I personally have never had to pH up fighting my entire first grow but that was because our tap water was about a 7.0 on its own. So, it’s definitely worth it to test your water before buying your pH up & down solutions.

* I use 2ml per gallon of water to bring the pH down about 0.5*

Testing Your Runoff

If you’re using soil, it’s a good idea to occasionally check your water runoff from watering your plants. This will give you a better idea of the pH of your soil. Once you get your pH fine tuned, you won’t really need to do this unless you suspect a pH issue.

Now, you should have a better understanding of the importance of pH levels when growing cannabis. You will be better prepared to check your pH, pH balance your water and pH up & down with ease.

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