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Managing pH in my cannabis grow: How to check and adjust the pH of water


Why is pH important when growing marijuana?

It all has to do with nutrients. Different nutrients get absorbed at different pH ranges.

You see, he pH of your marijuana plant's root zone is very important to preventing nutrient problems with growing marijuana. This is because when the pH is too high or too low, the plant's roots will not be able to absorb nutrients properly.

Take me straight to the marijuana root pH Charts!

As a result of the pH being too high or too low, cannabis plants may start showing signs of nutrition deficiencies even if the nutrients are available in the growing medium.

Glistening trichomes on Northern Lights buds - most growers need to check pH to grow buds this happy

Yes, that's worth repeating. You will prevent nutrient problems by checking and adjusting your pH in your marijuana grow.

In fact, feeding your plant with the incorrect pH is one of the most common reasons that plants develop a cannabis nutrient deficiency. At least when growers write in to us, incorrect pH is the cause of a nutrient deficienty at least half of the time.

So if you want to see glistening trichomes on your marijuana, like the picture to the right, make sure you check and adjust the pH of your water and marijuana root zone.

How to Test the pH of your Root Zone

You can test the pH of a water sample using a pH Kit or a pH Meter. If growing your weed in water, take a sample of the water and then test the pH of your sample .

If your weed is growing in soil or another sort of medium, the easiest way to get a ball-park figure of the root pH is to test the water going into the plant as well as the water that runs out of the bottom.

You can assume that the pH of the water that runs out the bottom of your plant is about halfway between the pH of the water you put in and of the pH of the root zone.

So for example, if you water your plants with water that has been pH'ed to 6.0, and the water that comes out the bottom has a pH of 6.5, you can assume the pH of your root zone must be around 7.0, because the water that came out was 6.5, which is halfway between 6.0 and 7.0.

When trying to adjust the pH of your root zone, make sure to do all changes slowly. It is actually worse for your plant to have the pH change drastically than it is for the plant to have roots in the wrong pH.

Adjust the pH of your Water to Correct Root pH

You will need to add all of your nutrients to your water first before checking and adjusting the pH. Your nutrients will affect the pH of your water so it's important they get added before making any adjustments. 

It's a good idea to let the pH cover a range instead of always adjusting to the exact same pH number. Some nutrients are better absorbed at slightly higher pH readings, while others are absorbed better at lower pH readings. 

If your marijuana plant roots are experiencing the wrong pH, the most important thing to remember is to make all pH changes to the root zone slowly (never more than 0.5 points in a day) because rapid changes will hurt the plant much worse than being at the wrong pH.

For soil an optimum root zone pH is between 6.0 and 7.0, with the most time spent with a pH between 6.2 - 7.0.

Growing marijuana in soil pH Chart

For hydroponics an optimum root zone pH is between 5.5 and 6.5. With hydroponics, it's especially important to allow the pH to range slightly, as some nutrients can only be absorbed at higher or lower pH's.

Growing marijuana in hydroponics pH Chart (including soilless mixes that include coco coir, vermiculite, perlite etc)

The thing to remember with pH is that you don't need to be exact. What you do need is to be consistent in keeping the pH from creeping too high or too low in your plant root zone.

Here is a video by me, Nebula Haze, which shows you how to easily check the pH of your water before you use it with your marijuana plants.

Buy a pH Kit from General Hydroponics which also comes with a dropper.

Watch my video on how to manage your pH on Youtube!

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