How Deep Do Cannabis Roots Grow?

How Deep Do Cannabis Roots Grow? (Answered)

When choosing the grow pot to use, you might want to know how far the roots can grow so that you use a pot with sufficient depth. 


Cannabis plants grow pretty fast, and some strains that grow big also reciprocate in the growth of roots. Their roots grow deeper into the medium and might be rootbound faster if you didn’t put their robust root growth into the equation when choosing the grow pot.


Another reason why you might want to know how deep the root grows is when you want the plant to gain all the nutrients. Nutrient leaching is common in some mediums, where the nutrients sink deeper than the roots, thus don’t get absorbed. 


You can’t talk about depth without breadth. Cannabis roots also grow horizontally, and when the roots stretch far into the sides, the pot will become limiting. So think breadth too. 


The cannabis plant spreads many secondary roots on the sides, but the taproot grows deeper into the growing medium, and you have to leave enough room at the bottom for its development. 


Taproots give the plant the stamina to withstand changes in the weather. It’s the only reason why huge plants grown outside can survive a gale. 


How Deep Do Cannabis Roots Grow?

Cannabis roots grow deep, with some strains growing deeper roots than others. The roots can grow up to 3 feet or more. Outside, the big plants can stretch the roots to 5 feet, but inside, since the vertical height is kept in check, 2-3 feet deep containers will meet the plant’s needs perfectly. 

How To Fix Cannabis Roots Growing On Top Of Soil

Factors That Affect How Deep Cannabis Roots Grow


Cannabis roots grow at different lengths because of different factors. It is important to consider these factors so that your plant’s roots always have enough room for growth;


The Grow Medium 

Cannabis roots grow in a pyramid-shaped structure. The taproots form the main stem of the roots, then fibrous roots grow on them and spread outwards, and then root capillaries roots grow from the fibrous roots. The root capillaries are mostly called root hairs and are essential in the absorption of water and minerals. 


When the wrong substrate is used, it can inhibit the growth and development of roots. Compact substrates don’t leave enough room for the root to spread, thus can reduce the depth of growth. 


And substrates don’t work the same. A substrate that works for one plant might not be suitable for another. If it works for tomatoes, it doesn’t mean you can use it for cannabis.  


Using the wrong substrate for cannabis also means the plant will not receive enough nutrients for proper growth and development. Plants grown in the wrong substrates exhibit lanky stems, slow growth, and sparse foliage.


For cannabis, coco coir is more forgiving because it’s not compact. It allows the roots to grow and expand easily. Growing in soil, on the other hand, will not be suitable for some strains. If the soil is too dense, add perlite to break it up. Cannabis thrives in soil that’s loose and airy; any cannabis strain won’t do well in dense soil.


Also, plants growing the wrong substrate will be more likely to suffer root problems, like root rot.


Watering Cycle

Roots are always searching for water and nutrients. It is the farthest they have to go to get these essential growth factors that influence their growth. The roots won’t grow if the substrate is always wet because they have nothing more to hassle for.


The plant needs water, but it also needs a season of dryness in the substrate to ignite the growth of the roots. Knowing how to balance between the dry and wet periods in the substate can help your plants develop a labyrinth of healthy roots.


Plants grow faster when the roots are robust. A network of well-tended roots absorb enough water and resources for the plant, hence a healthier growth and better yield. 

Don’t keep the substrate wet all the time as that hinders root growth and development

The Cannabis Strain

Some strains grow deeper roots than others. Most autoflowering strains grow shallow roots because they have a shorter life cycle. While for strains that grow big and take longer to mature, the roots will grow deeper.That’s why some strains do better when grown outside where the size of the pot doesn’t limit their roots. The clue to help you decide the right strain for the space and pot is to study how big it grows; the roots will need bigger pots for bigger plants. 


The Vegging Duration

If you’re going to veg for longer, then you need enough room for the growth of the roots. The best thing about growing weed indoors is the freedom it allows you when growing.


While other people prefer to grow many plants in the tent, others prefer to grow one big plant. The bigger the plant, the more you yield you get per plant.


Vegging is the period where you decide the size of the plant you’re growing. It is the phase where the plant experiences robust growth structurally. The longer you veg, the bigger the plant becomes. 


The bigger the plant grows atop the soil, the deeper the roots grow into the grow medium. So when you veg for longer, the roots will need a more liberating root environment to stretch favorably. 

How Deep Do Cannabis Roots Grow?
The roots often outgrow the container when you veg for longer


Related Read: Does Vegging Longer Increase Yield?


Do Cannabis Roots Grow During Flowering?

The roots continue growing during flowering but with little structural change.  The roots’ growth is a continuous process of replacing dead cells with living ones. However, root expansion occurs during the veg phase when the plant focuses on growth and building structural leverage.


During flowering, the plant will be using the robust root system it grew during veg as it focuses on the formation, fattening, and nourishing the buds.


If you’ve used smart pots, you might notice the hairy roots getting air burned outside the pot. These small hairs indicate growth. Since they also appear during flowering, they indicate the roots grow during flowering.


Frequently Asked Questions About Cannabis Roots Growth

When Do Cannabis Roots Stop Growing?

Cannabis roots do not stop growing. As long as the plant is alive, it will grow its roots. It’s only the intensity of growth that goes down during the later stages of the plant’s development. Two weeks after initiating flowering, the growth of the roots will slow down considerably. Still, the plant is always replacing worn-out root tissues, hence the slow-paced, almost unnoticeable growth. 
The roots don’t stop growing, but after the plant begins to flower, it will shift its energy from growing the roots and other branches to growing and nurturing the buds. 

How Fast Do Cannabis Roots Grow?

Cannabis roots grow pretty fast. You never realize how fast the roots grow until you plant in a small container and are forced to re-pot to a larger pot. In just a month after the transition from the seedling stage, the taproot shall have a deeper hold of the growing container. 
The secondary roots and the capillaries soon fill the horizontal space available. Still, the roots’ growth rate will depend on how well you keep the watering and feeding schedules.

How To Make Cannabis Roots Grow Faster

According to the REV, the author of True Living Organics, using cooler lights of the blue spectrum encourages faster root growth than using lights of the redder spectrums. Thus, after cloning, using blue spectrum light can help the plant root faster. Also, ensure the roots are getting enough oxygen by breaking up the substrate with perlite.  
However, there’s limited literature on the pace of cannabis root growth. The closest research was done on Hemp roots, where they found the roots to have grown 200 centimeters after a year. 

In conclusion, cannabis roots grow deep when the grow medium is loose and easy to penetrate. The plant’s roots can only grow farther when they strive to get water and nutrients. Thus, overwatering can inhibit root growth and make the plant more prone to root ailments.


Always leave enough room for the plant to grow and thrive. If there’s one thing weed growing gurus agree on, it’s that you should never limit the growth of cannabis roots. 


External references:

  3. True Living Organic by The REV