Grow Tip: The Importance of the pH Level

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Grow Tip: The Importance of the pH Level

Way back in school you may have learned about a little something called pH. Well, it’s time to put that knowledge to use, because you guessed it, pH is important if you want to grow good cannabis.

Learning about pH, and how it affects cannabis, can make all the difference if you are looking to hone your cultivation skills. Sure, you can get by without knowing about it, but monitoring and controlling it can go a long way to help push you into the echelons of veteran growing.


For those of you who can’t remember those bygone days of sitting in the science lab at school, pH is a scientific measurement used to define how acidic or basic (alkaline) a substance is. This measurement uses a scale, ranging from 1-14. Anything below 7 is considered acidic, and anything above 7 is considered alkaline. 7 itself is neutral.


Knowing what the pH of your growing medium is, and how to control it, is all very important if you want to increase your chances of a successful grow. This is because pH effects the ability of a cannabis plant to absorb nutrients; if the pH of the plant’s growing medium strays outside of what is considered safe, nutrients begin to become unavailable for absorption, no matter how many are present.

Why? Well, let’s consider soil that has become too acidic. In this situation, acidic salts within the soil will bind to nutrients also present, fundamentally changing them and making them impossible for the roots to absorb. As such, a problem that may appear to be a nutrient deficiency could actually be caused by an uncontrolled pH. It is something that often catches novices out, making them think their plants need more feeding, which only leads to more problems.

So if your cannabis ever looks like it has a nutrient deficiency, always check you pH first!

The ideal pH for soil is 6.5-7.0.

The ideal pH for a hydroponic system is 5.5-6.0.


The good news is that it is actually very simple to monitor the pH levels of your cannabis grow.

The simplest and most accurate method is to use an electronic pH reader. These are super easy to use, and can be quite cheap, costing anything for €5-€60 depending on how fancy you want to get. You simply pop the probe in a wet growing medium, and you get a pH reading on the dial.

There are other methods, such as using pH paper, but this is a much more antiquated method, and open to a lot of error.


Loads of things effect the pH of your growing medium, even tap water will alter it. For this reason, it is important to know how to control it.

The best way to do this is use shop bought pH-up and pH-down. These are excellent ways to control the level of your pH no matter what growing medium you are using. They are inexpensive, and are often simply added in with the next watering. However, they can be very strong, so be sure to follow the manufactures instructions precisely!

An alternative method when growing in soil is to use dolomite lime. Dolomite lime has a pH of 7, so can easily bring your soil back into balance no matter what its current pH is. For soil, it may actually be worth using this first a couple of times before considering pH-up or pH-down, as it is much more natural. However, dolomite lime contains quite a large amount of magnesium and calcium – more than your cannabis is likely to need. So if you use dolomite lime all of the time, it could cause a nutritional imbalance.

If you are feeling confident in your abilities, you could even try making your own fixing solution. All natural plant feeds and natural soil additives have an effect on pH; if you can get a reading from some of the resources you have on hand, and know how to mix them for cannabis, you can exercise a great deal of control of the pH situation. Heck, even coffee granules have been known as a garden remedy for certain pH levels.

What is important is that you know that pH is something that effects your grow, and that you need to monitor it. Once you realize this, you have won half the battle, and can actively work to control it. Good luck!