The Effect of pH on Cannabis Growth: Why the Right pH is Important for Healthy Plants

06. 11. 2023

Various factors such as air, water, sunlight and soil quality influence the cultivation of cannabis and the quality of the final product. Although it may seem like a complex subject at first, knowing the pH value is essential for growing healthy cannabis plants. In this article, you will learn everything you need to know about the importance of pH when growing cannabis and how you can change the pH value.

What does the pH value mean?

ThepH value is used to measure the acidity and alkalinity of liquids or dissolved solids. The pH ranges from 0 to 14, with pH 7 being neutral. If the pH is below 7, the substance is said to be acidic (vinegar or lemon juice). If the pH is above 7, the substance is referred to as alkaline (soap or bleach).

Cannabis plants thrive best in slightly acidic soil with a pH between 6 and 7. When growing cannabis hydroponically, the ideal pH is between 5.5 and 6.5.

Why is pH so important when growing cannabis?

The pH value of the soil is important for proper plant nutrition as it directly influences the supply of nutrients to the plants. Every cannabis grower knows that the growth of cannabis is dependent on nutrients and minerals. The soil needs to have enough of the main macronutrients, which are nitrogen, phosphorus and potassium. If the pH is lower or higher, the plants will not be able to absorb certain types of nutrients and after a while they may show signs of a deficiency or excess of certain nutrients, as certain types of minerals build up in the growing medium, creating a toxic environment for the plant roots and preventing the absorption of other nutrients.

What is the ideal pH for cannabis plants?

Every grower needs to create the ideal pH for their plants, as individual plants vary in genetics and growing environment.

Growing in soil

When growing in soil, a pH between 6.0 and 7.0 is best for cannabis, but there is no specific number that is the best within this range. On the contrary, it is advisable to allow for some natural fluctuations within this range to encourage optimal nutrient uptake.

If you grow completely organically, without the use of chemical nutrients, the pH value does not matter so much. The use of natural fertilisers such as compost creates a fertile breeding ground for beneficial bacteria that maintain optimum soil conditions, and therefore it is usually not necessary to monitor the pH of the soil as closely as in other cases.

Hydroponic growing

In hydroponic growing, the pH varies. If you are growing without soil, for example in a coconut tree, the optimum pH should be slightly lower than in soil, between 5.5 and 6.5. This also applies to all hydrotechnical methods. As with growing in soil, it is fine if the pH level fluctuates slightly, but always ensure that it stays within a safe range.

How do I find out the pH value of cannabis soil?

Checking the pH level involves testing the water or nutrient solution and then adjusting it. The easiest way to measure pH is with a digital pH tester, which you can simply stick into the soil to get an accurate reading instantly. You can also use pH test strips. Just put some soil in a jar and mix it with an equal amount of neutral water. Then pour it through a coffee filter and use the pH test strip to check the pH of the water.

Adjusting the pH value

If the pH value starts to deviate too much from the desired value, adjust it in one of the following ways:

Using pH Down

It is more likely that the pH will need to be lowered than raised. To do this, add a small amount of pH lowering agent to the water or nutrient solution, stir, and then retest the pH. You can repeat this process until you reach the desired pH value.

Using pH Up

In exceptional cases where you need to raise the pH level, you can obtain a pH up solution, which has the opposite effect to the pH down solution. Simply add a small amount of pH up solution to the water until the pH level is equal.

Other ways to lower or raise the pH when growing cannabis

In addition to pH adjusting products, the pH of the soil can also be lowered or raised using various natural products. Effective remedies include:

Manure,
Compost,
lemon juice,
vinegar,
lime,
pine needles,
sawdust,
shells,
coffee grounds.

The main difference between organic and chemical pH adjustment products is that chemical products tend to destroy all natural life in the soil and therefore need to be renewed after each use. Organic products have no such negative characteristic, although slightly more product must be used to obtain the desired value than with chemical products.

What are the signs of high pH in cannabis?

The signs of high pH in cannabis can vary greatly and can include a range of symptoms associated with nutrient deficiencies. The usual bright green colour is often replaced by yellow leaves. Vigorous plant growth is halted and plant health deteriorates until the correct pH value is restored.

What are the signs of low pH in cannabis?

If the pH is too low, some micronutrients are absorbed in excess of what the plant needs and this can lead to a number of toxic effects. If the optimum pH is exceeded,mineral deficiencies will become apparent over time. It is therefore important to control the pH and address the problem immediately at the first sign.

Correct pH when growing cannabis

Controlling and regulating the pH of the soil or water is one of the key factors in growing healthy cannabis plants and achieving high yields. In fact, proper nutrient uptake requires careful control of soil and water acidity.