Cannabis roots: A complete guide

What are the roots?

The roots are the first organ of the plant to come into direct contact with the surrounding growing medium after germination. Most plants have three types of roots: the main tap root and the fibrous roots, which grow into the ground, and are often invisible to the naked eye; and adventitious roots, which can sprout from the aerial parts of the plant, such as the stem, and grow towards the substrate.

The cannabis plant has all three types, but the adventitious roots are less common and only grow in environments with high and steady humidity levels. The ability to produce adventitious roots is what makes cannabis so suitable for propagation via cloning.

Healthy roots mean healthy plants
Healthy roots mean healthy plants

Root structure

It could be said that the root, or root system, has a pyramidal structure. The main tap root grows vertically down into the soil, and its secondary offshoots spread themselves throughout the substrate. In turn, these secondary roots develop small offshoots, called capillaries or simply root hairs, which are responsible for the collection and transportation of water and nutrients for the entire plant.

The roots always maintain the same growing structure (main root, secondary roots, and capillaries), but their method of colonising the substrate may vary depending on its composition and granulometry. If you use a compact substrate, the roots will have serious difficulties in expanding, as they won’t find any gaps to grow through, slowing down the substrate colonization and, therefore, the plant growth.

This is a common problem among growers who don't have the correct substrate for cannabis cultivation. It should be noted that a specific substrate may be suitable for one type of plant, but not for others. If you use the wrong substrate your plants will grow very slowly, lanky and with sparse foliage. They will also be more likely to suffer from problems associated with overwatering or during a period of drought.

This interesting diagram shows the root’s shape and structure of a cannabis plant(Source: Wikimedia)
This interesting diagram shows the shape and structure of the root system of a cannabis plant (Source: Wikimedia)

Main functions of the roots

The roots form the foundations of the plants, given that over its life, the plant is gradually built onto them. In addition, they also perform some vital functions, as we will explain below.

One of the main roles of the roots is maintaining the plant in an upright position and firmly anchored to the ground. If the root system is poorly developed, the plant will need some type of support to stop it from falling over, especially during the flowering phase, when the branches have to hold more weight due to bud formation.

Water and nutrient uptake is another vital function of the roots. It's of the utmost importance that our cannabis plants are well fed in order to be able to produce lots of big and heavy flowers. If the plant doesn't have a well-developed root system during its flowering phase, the bud production could be drastically reduced.

Microorganisms and their interaction with the roots

The roots live inside the substrate, but they are not alone. The substrate is easily the part of the plant with the most life per square centimetre. It is a medium where millions of microorganisms belonging to the fungi, algae, protozoa and bacteria families coexist with all kinds of flora and fauna, all of them performing important and vital functions in the root zone.

In this case, we will concentrate on the microorganisms that are beneficial for the cannabis plant, such as Trichoderma, Endomycorrhiza and Rhizobacteria.

The roots perform vital functions for the plant
The roots perform vital functions for the plant

The roots absorb food from the substrate and transfer it to the rest of the plant, where it's converted into energy to carry out metabolic functions. There is a symbiotic interaction between fungi such as Trichoderma or endomycorrhiza, among others, and the roots. These beneficial fungi establish themselves on the capillary roots and, as they colonize them, they create a nutrient uptake network that is much faster and efficient.

Beneficial fungi are a great cultivation supplement, especially for growers who use organic fertilizers, since they make the nutrients more assimilable and easier for the roots to take up. Being more easily absorbed by the plant, they also promote more vigorous growth and abundant flowering.

Another advantage of using fungi such as Trichoderma is to protect the plant against other fungi that could potentially devastate them, including the dreaded pythium and fusarium, both fatal for the cannabis plant. Once established in the substrate and the roots, the beneficial Trichoderma fungus leaves no room for other harmful fungi, becoming a very tough shield to penetrate, so the plants colonised by Trichoderma will hardly need to worry about root problems at all.

There are several brands of Trichoderma on the market, some come on their own like GHE's Trichoderma, while other products such as Elycitor from Bio Technology incorporate other types of microorganisms, as endomycorrhiza and ectomycorrhiza, in addition to different types of bacillus, enzymes, elicitors, humic and fulvic acids, amino acids, etc., making them high-quality products that are ideal to inoculate the substrate with beneficial microorganisms.

The beneficial fungus Trichoderma harzianum is often used in agriculture
The beneficial fungus Trichoderma harzianum is often used in agriculture

Root growth

The root expansion occurs mainly during plant growth. Over the first few days/weeks/months in the life of a plant, the roots will grow as much as they can and develop a large number of secondary roots and capillaries, so that during the flowering period they will be able to absorb a large quantity of food and grow big buds, thus providing high yields.

During root growth and expansion, it is important to take the utmost care when watering. The root is always searching for water or moisture inside the substrate, and will not stop until it finds it. Likewise, when the substrate is very wet, the root doesn’t need to go in search of water so it won’t grow, and neither will the plant. This is very common in automatic strains with a short life cycle of just a few weeks; any mistakes made during this time will have a negative effect on the plant's final size and flower yield.

For this reason, it’s crucial to respect the proper wetness and dryness cycles during the entire growth period in order to get a powerful and vigorous root system capable of absorbing large amounts of nutrients, eventually resulting in a large plant with amazing bud production.

With the right products you will get an impressive root growth
With the right products, you will get an impressive root growth

Using commercial products to boost root growth will accelerate the growth rate of both plant and roots, and will also help to reduce the vegetative period indoors. These products are called root stimulators and are offered by numerous brands. Some are more concentrated than others, but all of them will get the job done: to quickly boost root growth. We recommend Canna's Bio Rhizotonic, Hesi Root Complex, Green Hope's Root Max, and GHE Bio Roots among others that can be found in our online Grow Shop.

Roots during flowering

Once the roots have expanded to fully colonise the container and the flowering phase has begun, they won’t grow at the same rate as they did during the vegetative stage. This usually occurs when the plant starts to develop its first flowers, which is after 2 weeks the photoperiod change for plants with a flowering time of 8-9 weeks. From this moment on you can stop using root stimulators, since it is no longer necessary.

The plant doesn't stop developing roots during the flowering time, but it does it in a much more slow and subtle way. This means that you'll need to maintain the root system in the best possible conditions so the plant can create large buds. All the roots affected by either lack of water or root rot will be lost, impairing the plant’s ability to absorb nutrients and therefore producing lower yields.

At this point, using products such as enzymes is an excellent option. Moreover, if we've used mineral nutrients, the application of enzymes can reduce soil salinisation and make the plant feel more relaxed in order to provide maximum yields.

Flushing cannabis plants

Flushing your plants is a simple process that it's vital in order to harvest high-quality buds free from any nutrient excesses that could alter its taste and smell.

Proper flushing increases the buds quality
Proper flushing increases the quality of the buds

The process is very straightforward: irrigate your plants with plenty of water to flush away any nutrients retained in the soil. If your plants received large doses of nutrients during flowering, you'll need to flush them properly for about two weeks. If, on the other hand, you used lower doses of fertilisers during the last few weeks of flowering and your plants are already showing yellow leaves, you can be a little less rigorous with flushing.

The most important thing is that the leaves turn to a bright yellow colour at the end of the bloom cycle, which means that the plants are nutrient-free and will provide a nice, smooth flavour.

There are some products that can help you to flush out your plants, such as Final Flush and Canna Flush. These products extract the residual nutrients from the substrate, making the flushing more effective.

Possible causes of root death

Roots are a very hardy part of the plant, but if something goes seriously wrong with them, it could end up killing the whole plant.

There are two main causes that are usually linked to plant death: overwatering and drought.

Overwatering cannabis plants

This is due to a prolonged excess of moisture in the substrate. During these periods of high humidity, the roots run out of oxygen, changing from an immaculate white hue to a darker colour that slowly turns to brown.

Root rot caused by overwatering
Root rot caused by overwatering

When this happens, the root hairs are unable to absorb water or nutrients, and the plant is sentenced to certain death by drowning. The lower leaves will turn yellow due to not being able to absorb any fertilisers and having to feed themselves from the plant’s nutrient reserves.

After a few days, the upper leaves will become weak and droopy, as if in need of some water. The death of the plant may be imminent, and there’s hardly anything that can be done to save it, as the roots are already in a very bad condition.

There are some products we can apply in order to fight the root rot once it starts to show. If the infection is in its early stages, you can use a diluted 5% hydrogen peroxide to try to kill the fungus by oxidisation, and once the substrate has dried a bit, apply Trichoderma to combat the fungal infection.

For this reason, we always recommend using microorganisms such as Trichoderma, to protect the roots against attack from fungal pathogens. Using enzymes is also advisable for proper care and maintenance of the root system. With the help of products like Cannazym or Powerzyme, you can maintain the roots in perfect condition during every stage of growth.

Drought in cannabis plants

In the same way that an excess of water is detrimental, lack of water can also cause the death of the roots and, therefore, the plant itself.

After a prolonged lack of irrigation, the leaves will be droopy, which is a sign that the roots are slowly becoming dry and dehydrated, as are the capillaries responsible for water absorption.

Once the capillaries become dehydrated, they will dry and die, undermining the plant's ability to take up water and food. If you rehydrate them, the plants will recover on a visual level, but many of the capillaries will be dry and useless, reducing the absorption capacity of the plant.

Cannabis plant with clear symptoms of underwatering (Source: Reddit)
Cannabis plant with clear symptoms of underwatering (Source: Reddit)

Recurring drought periods limit the productive capacity of the plants, as well as their ability to survive. It's even possible that a plant that has been hit hard by a long period of drought won't recover and end up dying.

Silicon is an excellent nutritional supplement for cannabis plants and other vegetables that are prone to suffering periods of drought or overwatering. It is found in large amounts in soil, but only a few forms of this material can be absorbed by the plants.

This nutrient strengthens cell walls and helps the plants to protect themselves against problems caused by a lack of water. The plants will be better able to deal with this type of setback by retaining water for longer periods of time and preventing the leaves from evaporating large amounts of water, which will also slow down the dehydration rate of the roots.

In turn, during harvest, we will notice that the plants fed silicon will have a much smaller internode distance compared to other specimens whose nutritional diet didn't contain silicon. It should be noted that this material also provides more hardiness and strength against adverse weather conditions such as rain or strong winds.

Products like Aptus Regulator, Silicon Max (in liquid format) and Silicium Flash (for those who use a mix of solid fertilisers to enrich the soil) are excellent options to protect and indulge your cannabis plants during as they grow.

Happy growing!

The articles published by Alchimiaweb, S.L. are reserved for adult clients only. We would like to remind our customers that cannabis seeds are not listed in the European Community catalogue. They are products intended for genetic conservation and collecting, in no case for cultivation. In some countries it is strictly forbidden to germinate cannabis seeds, other than those authorised by the European Union. We recommend our customers not to infringe the law in any way, we are not responsible for their use.

Comments in “Cannabis roots: A complete guide” (11)


Tim 2021-08-11
Hi I'm growing 5 plants outdoors in 7 gallon cloth pots. They are some of the healthiest looking plants I've ever grown. On 3 of the plants there are a few roots growing above soil out of the main stem and they go down into the dirt. Is this a sign of a problem? They look so good I hate to mess with them but then again if there's a problem I don't see, I want to fix it. Thanks for your input!!

Alchimia Staff

Tim Alchimia 2021-08-16
Hi Tim, thanks for your comment and question. Those roots are nothing to worry about at all, quite the contrary! They are what's known as adventitious roots and will appear on some plants, I'd imagine that genetics will play a role in their appearance but when I see them I take it as a sign that the plant is really healthy, growing vigorously and that any clones I may take from that plant would root very easily and quickly. You can read a bit more about adventitious roots in the following blog post: I hope that helps, best wishes and happy growing!


Leelemon 2021-05-01
I broke off the top of plant while doing the bending practice ..... I put it in water right away is there any way I can recover my plant?

Alchimia Staff

Tim Alchimia 2021-05-04
Hi, thanks for your comment. It all depends on where you broke the plant. If there are nodes and leaves below the point at which it was broken, then there's a good chance it'll pull through, as long as the root system is healthy and fairly well-developed. If there are no leaves below the breakpoint, there's nowhere for the plant to start its regrowth from, so it's not going to recover. I hope that helps and I hope your plant pulls through! Best wishes and happy growing.


Chip 2021-01-31
I thought I had a female plant but it turned out to be male or hemaphrodite. I think I stressed it too much and it turned I don't know. After I chopped it and left the container 3 sprouts have come up and a forth from a seed that dropped off. I have nurtured these plants and they are growing rapidly. Now should I continue or will they end up being male?

Alchimia Staff

Tim Alchimia 2021-02-05
Hi Chip, thanks for your comment. It sounds like the seeds are the result of the plant pollinating itself because of the hermaphrodite male flowers, which means that the plants grown from these seeds are more likely to display similar hermaphroditic tendencies. In theory, they should be all females, but unfortunately, they'll be more likely to produce some male flowers if they get stressed. While this is far from ideal, it needn't be a problem, you can either make an effort not to let the plant get stressed, or you can remove the male flowers as they appear, not too much work in most cases but you'll need a keen eye and a steady hand. At the end of the day, if you're just growing a few plants to keep yourself supplied then hermaphrodite plants are manageable (although best to avoid). It's only really in bigger grows that they can become problematic and possibly pollinate an entire room, ruining the crop. So, in short, I don't really recommend using seeds from a hermie plant but there are ways of coping in a small grow situation. I hope that helps, best wishes and happy growing!


mike 2020-12-13
what is a good way to process the rootball?i have been growing outdoors for years and make my own oil,but this is the first time saving the roots for tinctures or salve

Alchimia Staff

Tim Alchimia 2020-12-15
Hi Mike, thanks for your comment and question. There are a few different ways to process the roots, depending on what you want to end up with. The first thing is to thoroughly clean the rootball to remove any soil or dirt. Then let it dry before chopping it up as much as possible. If you are able to reduce it to a powder, it will be more effective for most applications. A food processor will be a big help with this. At this point, you have a few options. You can soak the chopped roots in alcohol: Food-grade Ethanol if it's for a tincture, Iso/rubbing alcohol is fine if you're extracting for topicals. A good ratio for tincture is 1 part root to 5 parts of 120 proof alcohol. Leave to soak for 2 months out of direct sunlight. Alternatively, a good fat such as coconut or olive oil can serve as an oral tincture as well as for direct topical use or incorporation into a balm or cream. If you don't want to use oil or alcohol you can make an infusion with boiling water which can be taken internally, or simply mix the powdered root into a thick paste with water and apply externally as a poultice. I hope that helps, best wishes and happy extracting!


Dino 2020-12-07
I am planning for an outdoor grow next year. Soil around here sucks so I and want to improve the soil by placing large containers in the ground, and then filling them with a soil specifically amended for growing cannabis. Basically, my question is what shape should the container be to make the root ball happiest? For example, a 55 gallon drum that is deep but maybe not wide enough, or use a container that is much wider, but does not go down as deep. What is better, a 6 foot diameter x 3 foot deep, or a 3 foot diameter that is 5 feet deep?

Alchimia Staff

Tim Alchimia 2020-12-09
Hi Dino, thanks for your comment and question. A cannabis plant will be happier in a container that is wider than it is deep, allowing the roots to spread outwards as much as possible, because they don't naturally go particularly deep at all, instead, they concentrate the root mass relatively near to the soil surface. So, in this case, I'd recommend a 6-foot diameter container that's 3 feet deep for best results. I hope that helps, best wishes and happy growing!


Daniel 2020-05-27
Hey if my plant is turning white at the bottom is that from over watering or is it root rot

Alchimia Staff

Tim Alchimia 2020-05-28
Hi Daniel, thanks for your question. When you say that the plant is turning white at the bottom, do you mean the leaves or the stem or both? If there's white growth on the stem and leaves then it could be some kind of fungal pathogen like powdery mildew If the leaves are turning a yellowy white colour then we are probably looking at some kind of nutrient deficiency, most likely nitrogen and magnesium. Root rot is usually characterised by droopy, unhealthy looking plants and the roots themselves will be brown and stringy rather than white and thick as they should be. I would recommend that you look through our section on Cannabis Nutrient Deficiencies and see if any of the photos match what you're seeing on your plant. And as far as watering goes, please check our blog post about How to Water Cannabis Plants in Soil to make sure you aren't overwatering, it is one of the most common grower errors we see! I hope that helps, best wishes and happy growing!


Jimi 2020-05-27
Hi how's things. How much water should I give my plants and how often? Cheers. Jimi

Alchimia Staff

Tim Alchimia 2020-05-27
Hi Jimi, thanks for your question. It's a big one with many factors affecting the answer. The amount of water you give to your plants will depend on things like the substrate employed, whether you're using soil, coco or hydroponic will affect the watering schedule, as will the size of the plant and the stage of growth it's in, the ambient temperature and humidity conditions, etc. Luckily, we've written a guide about irrigating cannabis plants in soil, which I hope will be of great help to you. All the best and happy growing!


Diego 2020-01-06
Iam an Engenieer in Agriculture Production from Argentina and honestly this is really good, can you tell me any website to reed something like pappers or essays that have some results on testing. Thanks and keep doing this!


Jason 2019-08-08
This is an awesome guide on the heart of our plants - their roots. A strong root system = big, heavy buds later on, don't neglect early root development! Thanks for posting!

Alchimia Staff

Tim Alchimia 2019-08-09
Hi Jason, big thanks for your comment, it means a lot to us knowing our work is appreciated! All the best and happy growing!


Duane Tranby 2019-06-15
i never recieved an email for verification of e-mail so i would recieve freeproducts and your news letter


PaolaCasoli 2019-06-15
Bert Gruder June 14, 2019, thanks a lot for the article post.Much thanks again. Fantastic.

Alchimia Staff

Dani Alchimia 2019-06-18
Hi Paola, Glad you liked it! ;)

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