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Ever Wondered What the Right PH Balance for Growing Cannabis is?

If you want nothing less than a healthy, thriving and productive crop, then you need to dial in your PH (potential hydrogen) properly. In this article, we discuss everything from the importance of getting the PH balance right to the optimal PH balance for hydro and soil as well as ways of ensuring that you have the ideal PH balance at all times.  

Getting the PH right is the key to productive cannabis growing because it plays a governing role in how well nutrients are absorbed and metabolised – which in turn, affects the overall health and development of your plants.  

PH – also known as power of hydrogen – is a numerical scale through which the acidity or alkalinity of a medium or solution can be determined – in this case, the medium or solution on which your marijuana plant is growing.  

Getting the PH values correct is absolutely critical as it impacts the roots system of the cannabis plant as well as its nutrient uptake capabilities. Therefore, when this value is ideal, growers can enjoy optimal growth for their plant along with superb yields.  

In addition, the correct PH values are also directly responsible for prevention of diseases and deficiencies – forging the pathway for vigorous and hardy plants that are also far less likely to be attacked by pests.   

PH values range from 0 to 14, while substances and mediums that are tested as ‘7’ are neither acidic nor alkaline (neutral value). In any case, the more values slide toward 0, the more acidic your soil or medium is; the higher this value slides toward 14, the more alkaline your solution or medium is.  

PH values can vary according to your substrate; they are generally a lot easier to monitor in soil due to its buffering capacity, as opposed to a hydroponic setup – owing to the fact that the growing medium is a lot more unstable than soil – meaning that minerals interact very quickly and any shortcoming need to corrected equally fast.  

Despite this game of ‘gentle PH balancing act’, even if you’re starting out as a beginner grower, the proposition of PH levels shouldn’t deter you – a basic understanding along with the correct equipment for measuring PH balance will make managing PH levels in your medium a walk in the park. 

Getting the PH Values Right 

Your cannabis plant growth medium requires two things to function at its full potential: PH balance and nutrient concentration. Imagine for a second that your growing medium is a transistor radio – dial in the correct numbers and you’ll have a yield that’s nothing short of excellent.  

No matter what your growth medium is – soil or soilless – we now understand that the correct acidity/alkalinity levels directly control how well your plant absorbs nutrients. Cannabis plant roots generally prefer an acidic environment, just so you know.  

If you’re growth medium is soil, you should aim for a PH range of 6-6.8. If your growing cannabis plants in a soilless medium, the ideal PH values should be between 5.5 and 6.5. In cases where your medium’s alkalinity level rises above 7.5, the roots will not be able to absorb the available manganese, zinc, iron, copper and boron ions from it.  

Subsequently, if the PH level shifts toward the acidity scale and goes reasonably below a value of 6, the roots won’t be able to absorb the magnesium, calcium and phosphoric acid because the minerals would have lost their solubility.  

Furthermore, if temperatures soar above 26°C and your medium’s PH drops to 5-3, the possibility of your plant getting attacked by fungal diseases becomes very real.     

Plants that are watered with the wrong PH level over the course of many days will not only grow at a significantly slower rate but also develop nutritional deficiencies. They will, therefore, be a lot more likely to get attacked by pests and pathogens. If this stroke of bad luck has already hit you, then a visual inspection will show weak and dull-looking plants, yellowish to brownish spots all over and generally discoloured leaves.  

Regulating PH in Soil  

The first thing to carefully consider here is to choose the right soil, or better yet, make your own. Remember that the substrate must be homogeneous – it should contain all the right elements in order for the PH to register a neutral value, which is typically 7 but can range between 6.5 and 7. One of the keys to a successful crop yield is the substrate.  

It is important to understand that PH levels are generally more consistent in organic substrates because they contain a range of natural elements which are responsible for regulating acidity and alkalinity levels – keeping the soil neither too acidic nor too alkaline. As an added bonus, they also play the role of a buffer to protect the root system. To ensure that you don’t run into any PH issues, it is always a good idea to thoroughly mix the soil until it is nice and stable, as well as homogenous.  

On the other hand, if you choose to grow your plants in an inert and neutral substrate such as coco fibre, you must pay extra close attention as you prepare the nutrient solution. PH regulators need to be used – ‘+’ to increase the PH level and ‘-‘ to decrease it – and you must also measure PH level every time you water the plant.  

Also, every 3 days, you will need to calibrate the digital PH meter although that isn’t the only option at your disposal. You can also use a liquid PH test kit, which can be time consuming compared to digital meters, but these are generally a more reliable and even cheaper method of measuring PH levels.  

Before measuring the PH level, however, you must first prepare your nutrient solution, ensuring that all nutrients are added to the water beforehand. For your convenience, here are default PH values for soil when your plant is in the growing and flowering stage: 


  • PH level: 5.9-6 for Week 1-3 
  • PH Level: 6.0-6.2 for Week 4-6 


  • PH Level: 6.2-6.5 for Week 7-10 
  • PH Level: 6.2-6.3 for Week 11-14 

It’s actually possible to avoid fluctuations in PH level altogether by using specific organic fertilisers. But with that said, checking manually always pays. Mineral fertilisers, on the other hand, require a lot of inspection since they come in the ‘chelate’ form; and, you will also need to combine them with certain organisms as well as micro-organisms found in the soil. This is required for optimal nutrient absorption and metabolism.  

The good thing about soil is that it lets you use a substrate with buffering capacity – this means that nutrient assimilation occurs gradually – if any mistakes are made and identified early on, they are easy to rectify.  

Regulating PH in Hydroponics 

When working with hydroponics as your growth medium, it is crucial to get the PH balancing act right from the outset, because the nutrient solution elements interact very quickly – any effects on your plants will be almost immediate.  

When it comes to hydroponics, 2 key values must be taken into account that are, in fact, directly inter-related – that is, PH and EC (electroconductivity). PH is responsible for ensuring that nutrients are properly absorbed in the solution while EC indicates the concentrations that are present. 

‘Balancing these 2 values is very important’ is actually an understatement – if you don’t get them right, adverse effects will quickly become apparent. For this reason alone, plants grown in a hydroponic garden have to be very closely monitored.   

Here are the default PH values for hydroponics with regard to the growing and flowering stages: 


  • PH Level: 5.5-5.7 for Week 1-3 
  • PH Level: 5.8 only for Week 4-6 


  • PH Level: 5.9-6.2 for Week 7-10 
  • PH Level: 6.3-6.4 for Week 11-14 

Keep in mind that when the growing period starts, young cannabis plants and cuttings need to have a PH value of 5.5; this will need to be slowly raised to 5.8 and then 5.9, during which the vertical growth of your plant will typically last anywhere between 10 and 14 days, although this can vary between different strains.  

By the 8th week, you should raise the PH to 6 and by the 10th week, this value should be at 6.2. And, during the last 3 weeks (known as the washing period), you must keep the PH value between 6.3 and 6.4, which will be maintained until harvest.  

It’s highly recommended that you use enzymes at least once a week – from the early flowering phase to the harvest phase. This will prevent mineral salts from gathering on the roots and clogging your hydroponic garden or setup. Just follow the manufacturer’s instructions, which in most cases, is a weekly dose, and you can easily steer clear of this problem.  

In Closing – How Often to Check PH Levels 

You should be doing this as often as you can. Balanced PH levels allow your plants to reach their maximum potential.  

So to conclude, check those PH levels every single week, your nutrient solution’s PH week prior to watering, your growing medium’s PH a few days post-feed, and the water’s PH level after drainage.  

Do all this, and you will have the correct PH levels and also prevent your plants from taking unnecessary damage.   

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Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.