Healthy Roots for Healthy Cannabis Plants and Higher Yields
8 min

Healthy Roots For Healthy Cannabis Plants And Higher Yields

8 min
Growing Seedshop

Healthy roots are the foundation of any successful cannabis grow, so you need to ensure you can support the roots and manage any issues that arise. Here's how!

Healthy roots mean healthy cannabis plants, and healthy plants mean higher yields. With that simple wisdom in mind, it’s clear why cannabis growers need to make sure the roots of their plants are healthy and supported. In this article, we’ll examine common root problems and show you how to prevent and manage them.

The Importance Of Healthy Cannabis Plant Roots

The Importance Of Healthy Cannabis Plant Roots

Although other parts of the cannabis plant are vital to its growth—such as the leaves—strong and healthy roots play particularly important roles in the health of your cannabis. After all, your plants utilise the roots to take in water, nutrients, and oxygen, which are all essential to plant development. But that’s not all they do:

  1. Roots are the major means by which plants absorb water.
  2. Plants take in most of their nutrients through the roots. The roots also store extra food for future use.
  3. The root system anchors plants into the soil and stabilises them.
  4. Roots produce hormones called cytokinins that promote cell division, (i.e. they promote growth) and regulate axillary bud growth and apical dominance.
  5. Roots can form a mutually beneficial relationship with beneficial bacteria and mycorrhiza, the latter of which are fungi that improve nutrient absorption.

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Symptoms Of Cannabis Root Issues

Symptoms of Cannabis Root Issues

Even if you’ve taken all the necessary precautions, root problems can always arise when growing cannabis. The fact that the roots are not visible when grown in soil doesn’t help matters either.

That said, there are various signs and symptoms to look for that will clue you in to the state of your roots’ health. However, with the roots being such a crucial component and affecting many aspects of growth, these signs can manifest in numerous different ways.

  • Yellow leaves
  • Curled leaves
  • Crumbly leaves
  • Brown spots on leaves
  • Burnt leaf edges
  • Leaves dropping
  • Slowed growth
  • Issues with water uptake

None of these symptoms by itself automatically signals a problem with the roots specifically. It could instead be issues with nutrient issues, over- or underwatering, pests, etc. that are causing your plants to send out a signal for help. By using a process of elimination, however, you can rule out the unlikely factors to see if it really is your roots that are suffering.

Moreover, if there are severe problems affecting the roots of your cannabis, the entire plant may take on a weak and sickly appearance, showing several of the above symptoms at once. This can be your clue that you are, in fact, dealing with root issues.

Common Reasons For Cannabis Root Problems (And How To Solve Them)

Let’s take a look at some of the most common catalysts behind cannabis root issues, and what you can do to mitigate them.

Overwatering Or Underwatering

Overwatering or Underwatering

Overwatering is one of the most common mistakes made when growing cannabis. It leads to many problems, from root issues (root rot) to problems with nutrient uptake to fungus and pest infestations.

If you believe overwatering or underwatering may be the source of your problems, you need to reevaluate your watering schedule and volume (how much you administer). While severe underwatering can ravage the roots, the risk of overwatering is much more sinister. As such, you’ll need to ensure you wait until the soil in your growing containers is dry to water you plants again. You can determine when to do this by sticking a finger into the soil; if it’s dry, you’re good to water again. If you still feel moisture, give it some time.

A better way to observe your plants’ status is to lift up their pots. If they’re heavy, the pots are still holding a significant amount of water. If they’re noticeably lighter, they are probably ready for a drench. And drench you should! Although you shouldn’t water your plants too frequently, it is important to really saturate the soil each time you do water, allowing 25% or more runoff to come out the bottom. From here, allow the soil to dry out fully again before another drench.

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Another tip: Water according to the age and size of your cannabis. A small plant (autoflowers, seedlings, etc.) will need much less water than a mature weed plant. Use adequately sized pots and common sense to determine the specific needs of your specimen.

Also, make sure that your pots have adequate holes at the bottom for proper drainage. Use saucers underneath to catch any runoff, but make sure to collect it so the roots aren’t sitting in stale water.

To solve all of these issues in one fell swoop, just opt for fabric pots!

Rootbound Plants (Container Is Too Small)

Rootbound Plants

As we alluded to earlier, rootbound cannabis results from spatial limitation. If your plants are growing in pots that are too small for their level of maturity, their roots will start growing in circles and overtaking the substrate itself. But how do you know if your cannabis is rootbound without looking at the roots themselves?

To start, you will notice slowed growth; robust development may come screeching to a halt out of nowhere. You may also see the roots coming out of the holes in your container. This is a sure sign the roots are desperate to expand, but have nowhere to go. Time to get a bigger pot! Transplant into pots of at least one size larger than their former home, although you can go a couple sizes bigger if your plants are past the early growth phase. This will give the roots plenty of room, allowing for max development.

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When And How To Transplant Cannabis Plants For Bigger Yields

Just be careful when transplanting, as the roots are sensitive and will take time to get used to their new home. Speaking of which, after you retrieve your plant from its smaller pot, you’ll need to use your fingers to carefully loosen the outer strands of the root ball so the roots have somewhere to grow. Otherwise, you may find the transplanting process to be more traumatic.

Problems With Ph Levels

Problems With pH Levels

Incorrect pH levels are another instigator of various root issues. But that’s not even the half of it, as pH problems will also cause issues with nutrient uptake (“nutrient lockout”), leading to sick and underdeveloped plants.

When growing in soil, the optimal pH level is 6.0–7.0. When growing hydroponically, shoot for slightly lower pH levels of 5.5–6.5. Ensure that your water or nutrient solution is always at the proper pH. Get a pH meter or pH measuring drops. With pH "down" or "up" products, you can adjust your solution to the correct pH level. Make sure you measure pH after you add nutrients to your water!

Root Rot

Root Rot

When the roots of your cannabis are rotting away, indicated by a brown and slimy appearance, this can be due to one or more factors. Poor soil texture—soil that is too compact and doesn’t drain well—no drainage holes in the pot, overwatering, or a combination of factors can all give rise to the pathogens responsible for root rot. The reason for this is almost always stagnant water and a lack of oxygen at the root zone.

What to do about it? Replant your cannabis into well-draining soil, and use fabric pots instead of plastic planters. Also, amend your soil with beneficial bacteria and fungi. Many of these feed on harmful pathogens, which will reduce the risk of root rot.

Temperature Too High Or Low

Temperature Too High or Low

When temperatures in your grow room are too high or low, this can also bring on issues with the roots. Specifically, excessively high temperatures at the root zone will promote the growth of harmful fungi and other pathogens.

The ideal temperature for growing cannabis is room temperature: 21°C. A couple degrees more or less won’t be much of an issue, but if temperatures are much lower or much higher than that, problems will arise.

If growing indoors, make sure to use fans to keep temperature in check. Sometimes, even opening a door or window is all it takes to create a healthier environment for your cannabis. Otherwise, look into additional cooling or heating systems for your grow room. Also, if you’re using a powerful HPS grow light and heat is a problem, consider switching to LED. These emit much less heat but can be just as powerful!

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Issues With Substrate Texture

Issues With Substrate Texture

How do you know if your growing medium/soil is not optimal for cannabis? Simple; if the water takes a long time to absorb into the soil, it’s not ideal. Although the water should not run right through the substrate either, it should quickly be absorbed by the medium. As mentioned, you’re aiming for about 25% runoff. If the figures are much lower than this—or much higher—your soil will need some amendments.

Cannabis prefers well-draining soil where moisture cannot stick around for too long. Commercial potting mixes for cannabis normally have an ideal texture, but this isn’t necessarily true if you’re using universal potting soil. You can improve the drainage of such soils by adding around 5–10% perlite.

If your soil is drying out too fast, you can instead add vermiculite. Similar to perlite, vermiculite is a heat-treated mineral that makes the soil airier. But compared to perlite, vermiculite has a better ability to store water. If you continue to see your soil drying out too fast, you can also transplant to bigger pots capable of holding more soil and more water.

Damaged Roots From Transplanting

Damaged Roots From Transplanting

Whether your plants are rootbound or not, transplanting can wreak havoc on the delicate root system if not carried out properly. Transplant your cannabis when the soil is slightly moist (but not wet) as this helps keep the old root ball together.

Cover the top of the soil with your hand. Flip the old pot over and carefully slide out the entire plant with its root ball, using your other hand to support it. If the root ball doesn’t easily come out, use a knife and carefully slide around the inner edge to free it. Don’t pull the plant!

Root Aphids

Root Aphids

Aphids such as spider mites are notorious for attacking cannabis plants. You can normally spot these critters on the leaves or, in the case of fungus gnats, on the soil using a loupe or even your naked eye. But your plant can also fall victim to aphids that feed on the roots, hidden from plain sight.

Here’s what you can do to control root aphids:

  • Don’t overwater your cannabis. Overwatering creates the ideal environment for root aphids.
  • Use sterilised soil.
  • Use yellow sticky traps to catch the adults.
  • Soak the roots of your plants in a mix of neem oil and water.
  • Kill the larvae in the soil with a mix of 1 part hydrogen peroxide to 4 parts water.
  • Cover your soil with perlite or sand. This prevents bugs from getting into the soil.
  • Use beneficial insects that feed on aphids: e.g. ladybugs, green lacewing. Use beneficial nematodes in your water/feed to kill pests dwelling deep in the soil.

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Tips For Healthy Cannabis Roots

Given the various important roles the roots have, this also means root-related issues (which we’ll cover further below) will almost always result in problems in other parts of the plant. If left to persist, you can then expect anything from poor yields to severely sick plants. Having learned that, let’s look into how you can support the health of your cannabis plant’s root system.

Use Fabric Grow Pots

Use Fabric Grow Pots

When grown in ordinary plastic or clay planters, the roots of your cannabis will eventually run out of space. Growing round in circles following the inner walls of the pot, the roots will soon take over all the space in the container, leaving little room for soil, which holds water and nutrients. Thus, plant growth comes to a halt. This "rootbound" state means your plant cannot continue to develop with vigour in these conditions.

Fabric pots are growing containers made from porous, breathable fabric. Grown in these, your plants won’t become rootbound. Instead, the roots are naturally air-pruned as soon as they reach the sides of the pot. The result: healthier roots and stronger plants. Since fabric pots are porous, they also make it nearly impossible to overwater, which also benefits the roots significantly.

Don't Feed Cannabis Seedlings

Don't Feed Cannabis Seedlings

Many cannabis growers make the mistake of feeding their seedlings. Don’t! Your cannabis babies will do best without any supplemental nutrients for at least 2–3 weeks. Not only will feeding your seedlings increase the risk of various health issues, but it will limit their development too. Not feeding them in the beginning forces the roots to seek out nutrients, expanding the root system in the process. If you spoil your plant too early in its life, it will have no reason to develop strong roots.

Pro tip: Most commercial potting mixes for cannabis come pre-fertilised. Although you can germinate and grow seedlings in it, it’s better to use non-fertilised starter soil for this purpose. Don’t feed until several weeks after germination, when your plants have reached at least 10–15cm in height. When you do start feeding, use only 50% of what the bottle recommends to ease plants into their feeding regimen.

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Use Beneficial Microorganisms / Mycorrhizae (Fungi)

Use Beneficial Microorganisms / Mycorrhizae (Fungi)

Amend your soil with mycorrhizal fungi. These life forms attach themselves to the roots of your plants and increase their capacity to take in nutrients, in exchange for sugars secreted by the roots. Using mycorrhizae to boost the health of your roots is easy: All you need to do is add mycorrhizae to your soil once at the beginning of your grow.

Along with mycorrhizae, there are various other types of microorganisms that can improve soil conditions. For instance, if you’re growing organically with compost teas and other natural soil amendments, this will create the ideal environment for beneficial bacteria to thrive, which will in turn boost the development of your cannabis.

Supporting Healthy Cannabis Roots: Bottom Line

For healthy and vigorous development, it’s important that the roots of your cannabis plants can grow uninhibited and with all the resources they need. If everything is optimal at the root zone, a great harvest is just around the corner!

Happy growing!


Written by: Georg
Based in Spain, Georg spends a lot of his time not only geeking out at his computer but in his garden as well. With a burning passion for growing cannabis and researching psychedelics, Georg is well versed in all things psychoactive.

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