Cannabis cultivation in modern society has become something of an art form. While it is easy to plant some cannabis seeds and grow a couple of plants on your balcony, the ease with which we can spread knowledge now allows cannabis cultivation to get quite technical. One such specific area of knowledge that all cannabis growers should consider vital is learning about root health. It is no understatement when we say healthy roots make for a healthy cannabis plant, so we take a look at some of the common problems growers encounter, and how to deal with them.


From seed to bud, there is one part of the cannabis plant that plays a vital role in the plant’s health, and its importance cannot be emphasized enough – the roots. Roots are literally the foundation on which your cannabis grows, and are instrumental in the health of the entire plant. The main function of the roots is to uptake nutrients and water, and the rate at which they do it is directly linked to how large and healthy a cannabis plant becomes. Therefore, maintaining good root health is critical for a successful grow.

It may sound dramatic, but without healthy roots the rest of the cannabis plant will suffer – increasing the odds of reduced growth, wilting and yellowing of stems and leaves, disease, and death. To avoid that from happening, it is important to know how to maintain a healthy root system and to deal with common problems effectively.

Roots Cannabis Nutrients Feed Drainage Oxygen Plants



One of the most common problems among beginner growers is overwatering. As much as the roots need water, they also need oxygen to perform their functions efficiently. Oxygen is involved in many plant processes, as well as nutrient uptake. Without it, the roots will suffocate and become weak making them susceptible to pathogens. Being constantly soaked without any dry period also severely increases the risk of root rot.

In most cases, overwatering is the result of poor drainage, leaving roots to soak in water that they cannot drink up fast enough. This is particularly a risk in young plants, when the root base is still small. Always ensure your growing medium is well drained.

The initial signs of overwatering are leaves becoming firm and curled downwards. This is the plant taking in as much water as it possibly can – the leaves are literally bursting with water. This is an indication that you are watering too often and not allowing the growing medium enough time to dry. It is also means your roots are likely to be swimming in water. This later develops to root rot if not quickly resolved, causing numerous problems, including stunted growth, wilting, deformity, discolouring, and death. Basically, the roots become unable to function efficiently, starving the rest of the plant.

Preventing overwatering can easily be achieved. Learning how much water your plant is drinking and how soil feels when it’s in need of more water is fairly straightforward. A common test is to stick a finger in the soil up to the first knuckle. If it feels dry, it is about time to add more water. You can also determine when your plant needs water by checking the weight of the container. Carefully pick up a container after watering to get a feel for the weight. Repeat this when you are certain more water is needed, and make a mental comparison of the differences in weight. If it feels heavy, it’s probably too early to water.

Excessive Nutrient Feed:

Another common mistake when tending to cannabis plant is excessive nutrient feed. This does not damage roots directly, but excessive feeding in, especially with chemical feeds, can cause salts to build up in the growing medium, which in turn lockout nutrients from the roots, preventing them from being absorbed. This, in turn, damages the plant as a whole, and causes it to suffer from a feed deficiency – even though plenty is being but in the soil. For roots to do their job efficiently, levels of feed need to be controlled, and growing medium flushed if things get too salty.

Root excess nutrients

Roots Growing Space:

When growing in soil, another thing is frequently overlooked - the size of the pot or container where the seed is planted. Marijuana is a fast growing plant with roots developing even faster than foliage and stems above the ground. If not enough space is provided for roots to expand the plant will suffer from root binding. The root mass overcomes capacity of the growing medium itself making water retention and nutrient uptake impossible. Root-bound cannabis plant will experience stunted growth, dehydration, and yellowing of the leaves.

To avoid root-bound make sure you transplant your fast growing, young plants into a properly sized container. People often make a mistake by transplanting the young plant into the oversized container. It will eliminate root bound problem for sure, but there is a high risk of overwatering. The big sized container can take plenty of water, but a young plant with undeveloped root system can take just a fraction, leaving roots drowning in water – unless properly drained.

High or Cold Root Zone:

Keeping a steady temperature in the root zone is essential for happy roots. Cannabis doesn’t like big temperature oscillations and will most likely develop problems when faced with ones. Too much heat often becomes an issue when growing in hydroponic setups where heat decreases the ability of water to hold oxygen. Roots need oxygen to thrive, and they can easily get suffocated when exposed to high temperatures in hydro setups. Cold temperatures can also shock plants causing wilting and slowed growth.

Maintaining comfortable 22°C in the root zone will make your plants grow with no undesired side effects of temperature fluctuations. If struggling to do so, introduce additional air conditioning to your growing setup. It can be costly, but it can be a crop saver.

Roots Of Cannabis Plant

The Pathogen Invaders:

All of the previously mentioned stressors to the plant will weaken its natural defences, making it susceptible to pathogen attacks. There are two most common root zone pathogen bacteria that can wreak havoc to the plant if left unattended.

Rhizoctonia is a soil-born fungus whose attacks are more common in seedlings and young plants. The fungus causes root and collar root rot, cutting off supply from roots to the main stem. The fungus is visible in the soil producing thin white threads. The infected plant can develop red or brown spots on stems and leaves. Rhizoctonia thrives in overwatered mediums and high temperatures.

Pythium is the pathogen that is more dreaded between the two, and it’s certainly more aggressive. It thrives in hydro and aero setups where no soil based medium is present, but it can be found virtually anywhere. Pythium attacks weakened plants, causing root rot or “damping off”. The affected plants will experience stunted growth and yellowing of the leaves that will eventually die and fall off. The roots will become slimy and show unhealthy brown colour.

Keeping your growing room clean is the most effective way to prevent infestation, but even the tidiest grow rooms can’t repel some of the airborne attackers like Pythium. Introducing good bacteria to growing medium is a well-rounded way to fight off pests and can make a world difference in cultivating cannabis. They will not only eliminate the invaders but will form a symbiotic connection with your delicate roots increasing their absorbing capacity and making them stronger.


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One of the more popular beneficial bacteria is Mycorrhiza. It is a root fungus that inhabits the root zone of the plant. These fungi assist plants by feeding on nutrients, breaking them into more readily absorbed elements. The process allows roots to absorb nutrients at increased speed and capacity resulting in quicker growth and a more active development of the plant. Mycorrhiza can be bought in most of the hydroponic shops and adding them to growing medium is safe and extremely beneficial.

Another root helper is a fungus called Trichoderma. It is a very common fungus, present in most types of natural soil. It acts as root bodyguard by invading root zones aggressively, eliminating invaders competing for space. Besides the effect of killing bad fungi, it also penetrates a few layers of the roots, provoking the plant’s self-defence mechanism making the plant stronger and more resilient to any kind of stress.

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