pH and EC in marijuana growing

Philosopher Seeds always encourages its customers to monitor the water pH and EC when watering and fertilising their marihuana plants: if these values are properly adjusted and under control, we ensure that our plants absorb all the necessary nutrients, keeping them healthy, without any kind of deficiency and getting the maximum yields.

pH is the coefficient that indicates how acid or alkaline the water is. Later on, we will show you how a different pH range is required depending on the growing medium.

EC is the electrical conductivity of water; in other words, the amount of salts dissolved therein. The more nutrients we use, the higher EC values we'll get.

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pH and EC controllers

pH and marijuana

The first thing we should understand is that, even if all the necessary nutrients for the plant are present in the substrate, the plant can't absorb them if the pH level is not correct. The pH range required for optimal absorption of nutrients is different when growing in soil or on hydroponics. Here is a chart for both mediums.

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Nutrient absorption according to pH

pH is one of the most important factors when preparing the nutrient solution for our cannabis plants. It can be measured in different ways but, doubtless, if you want to be extremely accurate you should use a calibrated digital meter. Digital pH meters are lab tools with a delicate probe. They need to be handled with care and their maintenance is simple but it has to be done regularly.

The pH scale is usually measured within the range 0-14 (0 being the most acidic and 14 the most basic or alkaline).Taking pH 7 as the neutral value, your plants will need to be fed with a slightly acidic pH. You should always measure the water pH after adding all the fertilisers or stimulants to it, since these often alter the pH of the nutrient solution.

In the case of growing marijuana in inert substrates such as coco fibre or aeroponic/hydroponic systems, the pH value should never be below 5.5 nor above 6.3. The recommended pH acidity for the growth period is 5.5, raising it to 5.8 during the flowering period. This value can be slightly increased in late flowering for maximum absorption of all nutrients.

The recommended pH value for cannabis cultivation in soil is between 6 and 6.8.

Typically, a marijuana plant in the growth stage needs a more acidic nutrient solution than during the flowering stage, always keeping the range that has just been mentioned.

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pH should be adjusted also to water plants in soil

EC and marijuana

This is the second factor you should monitor in order to water and fertilise your plants correctly, and as with the case of pH, you will need a digital meter for better accuracy.

Measuring the water EC will be useful for:

  • Preparing the water with the right initial EC level in order to add fertilisers.
  • Checking the final EC of the nutrient solution after adding fertilizers and additives.

To start fertilising, the water EC should be near 0.4 (always measured in miliSiemens).This is easy to obtain if you start with RO water or rainwater (usually with an EC ranging from 0.0 to 0.2), and then simply add calcium and magnesium to the desired EC (0.4). If you don’t do so, your plants will probably show deficiencies sooner or later.

If you are using tap water, its quality will strongly depend on your geographical area.

Usually, if the EC is greater than 0.4 you should reduce it with distilled/RO water or rainwater until reaching that value. If you are lucky enough to have water with an EC level equal to or less than 0.4, you can add the fertilisers without having to lower the initial EC of your water.

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Preparing the irrigation water to add the nutrients (this meter measures in microSiemens)

It is difficult to establish a permanent EC table for all plants, as different genetics also have different nutritional needs (usually plants with higher Indica content can take more EC than Sativas), so at this point your experience and knowledge of the plants that your are growing will play a very important role. Also, in inert and hydroponic substrates higher EC values are often used. See these 2 plants from our catalogue as an example:


To succeed in growing Guayita you should take into account that it is not a demanding plant concerning the nutrients, so you should be careful in case it shows signs of over-fertilisation: dark green leaves and claw leaves are the most obvious symptoms. An EC higher than 1.6 in soil is not recommended for this genetics.

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Guayita from Philosopher Seeds

Black Bomb

By contrast, Black Bomb, due to its Indica dominance, demands a greater amount of nutrients. In fact, in our catalogue we recommend to increase the utrient concentration during weeks 3-6, as this will result in a spectacular high yield. In this case, and since this genetics can assimilate higher amounts of nutrients, we can use higher EC values. Following the previous example, during week 6 (in soil) you can feed the plant with an EC of around1.8 or even higher, mainly depending on the temperature and humidity conditions.

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Black Bomb from Philosopher Seeds

In the future we will publish some more technical posts on this subject, but we think that it is important that everyone understands the role of pH and EC in marijuana growing. We hope you have enjoyed this article.

All the best from Philosopher Seeds.

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About this Cannabis Blog

This is the blog of the seed bank Philosopher Seeds. It is intended for the use of adults over the age of 18 years.

You'll find information on homegrowing cannabis, tips, tricks and news from the cannabis sector.

To buy seeds from Philosopher Seeds and the best European seed banks. you can check out our cataogue.

(+34) 972 099 409
(+34) 972 099 409