Cannabis Growing Cannabis

Root Health in Cannabis Cultivation: The Comprehensive Guide

When growing cannabis, if you expect the plant to grow big and strong and to produce high yields, no matter what cannabis strains you’re growing, considering the root health is essential.

When it comes to producing vigorous plant growth, you absolutely need to consider the roots above all else, and what this really comes down to is the pH level.

The pH or acidity level of the soil that cannabis is growing in is perhaps one of the most important factors of all, because this directly impacts the health of the roots and their ability to intake nutrients.

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For the record, cannabis plant roots often prefer a slightly acidic environment. Now, you may also grow hydroponic cannabis, in which case root health and pH levels are also very important.

Although, hydroponic cannabis can be quite difficult to grow and requires a very extensive setup. For this reason, we’re going to focus on growing cannabis in soil, because this is what most people will do at home.

One of our main focuses for today will be allowing you to maintain an optimal pH range. Let’s get to it and allow you to grow a cannabis plant with a healthy root system.

Why Are Cannabis Plants Roots Important?

Cannabis plant roots are extremely important, and this is true for a wide variety of reasons.

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Nutrient Absorption

The most important function of the roots of a cannabis plant is to absorb essential nutrients from the soil, including phosphorus, nitrogen, potassium, and other essential nutrients that the plant will need for growth, flowering, and more.

Water Absorption

The roots of a cannabis plant are also very important because they are what take in the water from the soil. Water is required for a plant to perform photosynthesis, and without it, a plant cannot grow.

Stress Resistance

A cannabis plant that has a very healthy root system is also one that can withstand many different stressors, such as extreme temperatures, nutrient imbalances, and droughts.

The simple reality is that the stronger the root system is, the faster it can recover if the plant is suffering some kind of stress. Keep in mind that a healthy root system is also much less susceptible to pathogens and diseases.

Support and Anchoring

Another extremely function of the roots of a cannabis plant is to provide support and anchoring. The root system is what anchors the weed plant down in the soil, which provides support and stability.

As cannabis plants grow big and strong, this is very important. If the root system is not strong enough, it literally won’t be able to hold the plants up.

An Energy Reservoir

Although most people don’t know this, the roots of a cannabis plant also serve as a fantastic reservoir to store carbohydrates and other compounds that are rich in energy.

When the plant is growing rapidly or stressed out, it can draw on these energy reserves to support itself.

Using Microbes to Their Advantage

The root system of your cannabis plant can also engage in microbial partnerships. There are plenty of symbiotic relationships with beneficial soil microbes that can help protect against pathogens, enhance the health of the plant, and improve overall nutrient uptake.

How Do pH levels Affect Root Health?

One of the most important things to remember here is that the pH levels, which is how acidic the soil is, directly impacts the health of the roots.

For the record, the pH scale ranges from 1 to 14, with 1 being extremely acidic and 14 being very basic. Cannabis prefers a slightly acidic environment, with the correct pH level being anywhere between 5.0 and 7.0, with a soil pH level 6.0 being ideal.

Therefore, you want to make sure that you have a proper pH meter to provide you with a constant pH reading so you can make adjustments if needed. This pH range is extremely important to keep in mind. If the pH level falls outside of the optimal pH range, you will have problems.

This means that adjusting pH is something you’ll need to know how to do. However, before we talk about how to adjust pH levels in your cannabis plant soil, let’s find out why the pH level is so important for the overall root health of your cannabis plants.

Root Development

Having the optimal pH level for cannabis growth is essential for root health because they prefer a slightly acidic environment. Having a slightly acidic environment will help support nutrient uptake and root health.

If the pH level is within the optimal range, root growth and development are much more likely to happen without any kind of problems.

Cannabis plants actively expand their root systems during both the vegetative and flowering stages, which makes this just that much more important during these times.

The Microbes

Having the right pH level is also very important for the roots because it effects the types and amounts of beneficial microorganisms present in the soil. This includes mycorrhizal fungi and other types of beneficial bacteria.

These  microbes play an important role in breaking down a variety of organic matters, improving nutrient availability, and they help protect the roots from a variety of diseases and pathogens as well.

Differing soil pH levels can directly influence the activity and composition of the microbial communities, which ends up impacting brute health.

Nutrient Uptake – The Issue of Nutrient Lockout

By far the most important aspect here is that the roots of cannabis plants won’t be able to function properly in terms of nutrient and moisture uptake if the pH level is off. If the pH level is well above 7 or below 5, it means that nutrients will not be properly absorbed by the cannabis plant.

For instance, if the pH is well above 7, nutrients such as zinc, manganese, and iron become less available. If the pH level is well below 5, nutrients like calcium, phosphorus, and magnesium become less readily available.  therefore, the pH level directly affects nutrient uptake.

If pH levels are not within the optimal pH range for a prolonged amount of time, this will lead to what is known as nutrient lockout. In other words, your cannabis plants will no longer be able to intake nutrients, which will quickly lead to their deaths.

What Factors Affect pH for Cannabis?

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So you can provide your cannabis plants with the healthiest roots possible, you need to know what exactly affects the pH level of the soil.

Once again, having the proper pH range is extremely important here, as this is the number one contributing factor to root health.

Therefore, it’s very important for you to know which factors affect the pH levels of the soil in your cannabis grow room.


One of the leading contributors to fluctuating pH levels is your nutrient solution. Depending on the type of nutrients you are using, particularly liquid fertilizers, they can have a big impact from the pH level in the growing medium.

Keep in mind that many fertilizers are extremely acidic and can lower the pH levels of a growing medium very quickly.

The pH level in the root zone can also be affected by how efficiently cannabis plants intake nutrients. Therefore, the types of nutrients you are using can have a direct impact on this.


Another contributing factor here is the water that you use to feed your cannabis plants. Most sources of tap water will be relatively neutral or very slightly acidic, which should be fine for cannabis plant growth.

That said, you want to use a pH meter or some kind of pH testing kit to measure the pH levels in your tap water. It may be the case that the pH levels are not within the ideal range, in which case pH adjusters or other solutions will be called for.

The Growing Medium

What also has a direct impact on pH levels of cannabis soil is the growing medium itself. There are plenty of different types of growing medium, such as regular potting soil, coco coir, peat soil, hydroponics cannabis, and more. Each of these starts with a slightly different pH level.

Temperature and Humidity

Although many people may not be aware of this, there are many environmental factors, such as humidity and temperature, that can affect pH levels.

This is because different humidity levels and temperatures can affect nutrient uptake, which in turns affects the pH level.

Size of the Container

The other factor that can affect the pH level of your soil is the size of container that you are using. Simply put, the larger the container is, the more growing medium you can have, and the less fluctuations there will be. The smaller your containers however, the more susceptible your soil will be to pH fluctuations.

Measuring Cannabis Soil pH Using a pH Meter

Seeing as the pH for cannabis roots is so important, it is therefore essential that you test for pH on a regular basis.

One of the best ways to test for cannabis pH is by using a digital pH meter. A digital pH meter will provide you with very accurate pH values whenever you test for pH. All you have to do is stick the meter in your water and nutrient solution, and there are special cannabis pH meters to test soil pH as well.

Remember, what you’re looking for here is either a neutral pH or a slightly acidic pH. What you are looking to avoid here are extreme pH levels when you take either water samples or soil samples. Just make sure that you get a high quality unit, because if a pH meter fails, it can cost you your cannabis plants.

It might also be ideal for you to have a spare pH meter, so you don’t have to worry about measuring pH levels in the event that your primary unit breaks. Once again, testing pH levels is the most important thing you can do here, and you need to do everything you can to avoid pH imbalances. It’s all about pH control.

 How to Lower pH Levels in Cannabis Soil

If your pH tester is telling you that the pH value in the soil is far too high, there are some things you can do to lower the pH level.

If the pH level is far too high, there are a variety of elements you can add to lower it. There are ammonium-based fertilizers as well as sulfur fertilizers, both of which can lower pH levels.

You can also add various types of organic matter like peat moss, compost, and others, which can help lower pH levels as they decompose. There are also special pH adjusters and chemical pH adjustment liquids that you can use to easily change the acidity levels.

How to Raise pH Levels in Cannabis Soil

On the other hand, if your pH meter is telling you that the pH level is far too low, there are also other things you can do to correct this.

First and foremost, using those special pH adjusting chemicals is one of the easiest way to go about this.

However, if you want a more natural way to raise pH levels in cannabis soil, using agricultural lime or a dolomite lime mix is ideal. You may also add wood ash from hardwoods, as these can raise pH levels.

Other Factors That Affect Root Health of Cannabis Plants

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Let’s talk about some other factors that can affect the root health of your cannabis plants.

The Growing Medium

Seeing as the roots are growing in a medium, it is the medium itself that can greatly influence the overall health of them. In most cases, regular potting soil that is supplemented with nutrients on a regular basis performs really well.

However, you can always add other substances into the soil to allow for better nutrient uptake and moisture control. Specifically, these include vermiculite and perlite. However, adding some coco coir into the mix is a good idea as well.

Vermiculite, perlite, and coco coir, when added into the soil, will allow for better moisture retention, drainage, aeration, and more.

These are all things that will directly contribute to root health. Remember to always use digital pH meters to test pH levels whenever you are setting up a new growing medium.

Moisture and Temperature Levels

Moisture and temperature levels are also extremely important. Cannabis plants require specific soil moisture levels and temperature levels in order to survive.

Soil that is either too wet or too dry, or too hot or too cold, are all factors that can hinder root growth. Furthermore, moisture and temperature levels can also cause the pH level to move out of the optimum pH range.


Also consider that there are many nutrients that are very important for the overall health of plant roots. These include, but are not limited to, nitrogen, phosphorus, potassium, calcium, magnesium, zinc, iron, manganese, copper, and others.

Final Thoughts

The bottom line here is that maintaining proper cannabis root health really comes down to providing your plants with a good growing medium that has a balanced pH level.

Fabian Raemy is an avid cannabis enthusiast and expert. He's been a part of the cannabis community in one way or another for the past 15 years. Whether cultivating or consuming, Fabian knows his cannabis inside out. In his humble opinion, there’s just nothing more rewarding than growing a great strain of marijuana and being able to take a puff of some home grown green.

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