Roots are the most important part of almost all plants. By absorbing water and nutrients they provide the necessary function for a plant to grow. Unhealthy roots will only result in underwhelming harvests, meaning they need to be looked after properly.
First time growers often underestimate the importance of taking good care of the roots. Cannabis roots that are happy and healthy are essential for vigorous growth and big yields. This article shows you why they play such a big role in the life of a cannabis plant.
What are Roots?
The root is the first growth after germination starts. There are 3 types of roots which can be found in the vast majority of plants, including cannabis.
The tap root is the main root which emerges from a seed after breaking its husk. It is the central pillar from which other roots grow. Offshoots from the taproot are called fibrous roots, which develop smaller root hairs (capillaries) that are used for the absorption of water and nutrients.
Adventitious roots can also develop in cannabis plants. These are roots which grow from the main stem as an attempt for the plant to root itself. Cannabis plants are perfect for cloning because of their ability to grow adventitious roots.
Root Structure
The way roots branch underground is very similar to the plant growth pattern above ground. Unless they are clones, cannabis plants always have the same structural root growth - tap root, fibrous roots and capillaries.
Different containers affect the overall structure of roots as they will grow where they need to to find water/nutrients. This is why a lot of growers choose to transplant, because it allows roots to spread themselves more efficiently within the growing medium of the final container.
The density and structure of the growing medium will also determine how roots expand within their container. Roots will find the easiest way to reach the needed resources but if they have to use too much energy pushing through growing medium to find them, it is likely they will suffer.
The Function of Roots
Without the roots a plant would not grow. They are the foundation from which a cannabis plant supports and grows itself. This is why roots need to be taken care of with the utmost care. The aim should be to give roots the conditions they need to function to their full potential.
There are 2 main functions of the root system:
- Transfer of water and essential minerals - capillaries growing from the fibrous roots are working hard to transfer everything the plant requires for explosive growth.
- Support - roots form the base structure which holds a plant up. A well developed root system means a cannabis plant will have enough anchorage to support the production of heavy buds.
Root Growth
Roots grow mostly in the vegetative part of a cannabis plant's life so that by the time they reach flowering there are plenty for the easy uptake and transfer of nutrients to the flowers.
Giving cannabis plants a proper wet and dry cycle throughout their life means healthy root growth. The way to do this is by providing roots with good amounts of oxygen in between watering. Oxygenated roots is key to achieving big plants with high yields.
Root boosting supplements can also be used in the early stages of plant growth to maximise root development and efficiency.
- Germination - Once a seed recognises it has water surrounding it the tap root will sprout and grow as it finds a substrate to make a home in. Roots like temperatures of around 20 - 24°C.
- Seedling - Plants start to develop secondary roots (fibrous) as the plant finds support within the growing medium. Small root hairs shoot off and begin their search for nutrients.
- Vegetative - By this stage there should be lots of fibrous roots and capillaries. There is an increase in water/nutrient absorption, accelerating plant growth. The plant is well established within the growing medium as it prepares to flower.
- Flowering - Root growth slows down massively. From this point the roots are focusing on delivering water and nutrients to the flowers. Roots still need taking care of so be careful not to overwater during this phase.
Tip: Roots will not search for water without a dry cycle, resulting in small plants with low yields.
NuggetPawn from GrowDiaries has taken good care of his plant's roots from the beginning.
Flushing
Flushing simply requires you to feed your plants with only water, usually for 2 - 3 weeks before harvesting. This will help to flush out any excess nutrients still surrounding the root structure, leaving you with plants that taste and smell much better.
Well flushed cannabis buds have cleaner, smoother flavour and aren't so harsh when smoked.
Eventually, towards the end of the flowering period, plants start drinking less and their leaves turn yellow. These are good signs that the roots are slowing their function as plants use up the remaining store of nutrients. If plants have dark green leaves when flowering finishes it could mean there is still too much mineral content.
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Feeding Schedule
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Flush time
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Yellowing Leaves
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No Feeding
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0 weeks
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Too early - plant may use its resources before buds have finished developing
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Light Feeding
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1 week
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Early - leaves yellow faster as plant begins to use stored nutrients
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Normal Feeding
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2 weeks
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On time - foliage should still be mostly green and then turn yellow once flushing begins
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Heavy Feeding
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3 weeks
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Late - yellowing arrives later. Nutrient-free plants are not normally completely green when harvesting
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Roots Problems
If you do not notice problems underground, signs of unhealthy roots will begin to show through the leaves. Growing in soil means roots are not visible, making it harder to monitor their health. Although roots should not be exposed to light, hydroponics systems give the possibility to check roots more easily.
Problems often start at the roots so check your plants regularly for any unusual changes. If you notice slow growth, deficiencies, drooping or curled leaves, there could be an issue with the roots.
Plants that are still small enough can be checked by turning the plant upside down and carefully removing the pot as if you were transplating.
Overwatering - Roots become deprived of oxygen, growth slows and there is a risk of them rotting.
Solution: Use an airstone in your pot/reservoir to prevent algae or rot. Infections can be treated with hydrogen peroxide but make sure you check the strength first and dilute accordingly.
Underwatering - If roots dry out too much it can seriously stunt or kill a plant. Once roots dry out it is very hard to save them. Underwatered plants may survive but yields might be affected drastically.
Solution: Get into the habit of watering less, but more frequently. Irrigation can be set up on a timer although you should be regularly monitoring incase of failure.
Over fertilizing - Nutrient solutions can be too strong for roots and cause 'root burn', limiting growth and absorption of minerals.
Solution: Flush overfertilized plants with water. Once plants have stabilized and started showing new growth you can begin feeding again. Start with small quantities of nutrients and work your way up. Never use more than the recommended amount.
Conclusion
We can understand a lot through the appearance of a cannabis plant, but what is happening below the ground is equally as important. Neglecting your roots will only lead to disappointing harvests or failed grows, so pay attention to your watering schedule and give them plenty of oxygen.
Now you've learnt about the importance of roots and their function, you can use this knowledge to grow even better plants! Leave your thoughts and tips below, we'd love to hear from you.
External References
Analytic Models to Predict Root Structure Depth. - Shi, Xijin & Hsieh, Sheng-Jen. (2020).
Chemical and Biological Studies of Cannabis sativa Roots. Medical Cannabis and Cannabinoids. - Elhendawy, Mostafa A & Wanas, Amira & Radwan, Mohamed & Azzaz, Nabil & Toson, Elshahat & Elsohly, Mahmoud. (2018)
This article was updated August 2020.
