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marijuana root rot

How To Identify And Treat Cannabis Root Problems

Cannabis root problems are usually called as root rot. Problems in the roots can be caused by different organisms such as bacterias, fungi, and parasites and although the symptoms are similar, they don’t always look exactly the same.

1. What Is Root Rot?

Root rot is a condition that can ultimately kill plants. This condition affects roots when they are not in an optimal environment and affects them when they’re more vulnerable, especially when they are already stressed or shocked.

Organisms as bacterias, algae, and fungi (among others) will attack the roots, making them into brown slime. This brown slime is unable to absorb nutrients and water and in most cases is impossible to fix them.

2. Root Rot Symptoms

Because the first symptoms of root rot occur under the medium, growers are often not aware of the problem until it is more serious.

Cannabis root rot can cause leaf symptoms that can look like any deficiency: cannabis leaves get burnt edges or tips; yellow or brown spots, nutrient deficiencies, and curled edges among others.

When plants start showing the consequences of root rot, such as yellow leaves or stunted growth it may be already too late.

3. What Causes Root Rot?

Root rot occurs when the roots are affected by a bad organism after they are already stressed. Root stress can be caused by any of the following things:

• Excessive Heat

Roots in a hotter medium have a tendency to develop problems associated with fungi and bacterias.

• Excessive Cold

Cold roots are unhappy roots, low temperatures in the medium can shock the roots and can cause wilting among other problems, resulting in root rot.

• Overwatering

Too much water tends to attract some type of bugs that reproduce in wet mediums and may drown your roots, both of these problems will result in damaging the roots.

• Thick Medium

If your medium is too thick, it may prevent the roots from being able to get oxygen.

• Big plant in a small container

When your plant has overgrown the pot it is in (meaning the pot is too small for your plant to develop properly) you increase the chances of developing root rot. If you reach a point where the roots need to grow more but they can’t due to not having space, they will start to rot.

• Hydroponics

Root problems are common in hydroponics, this happens when you don’t use an air rock to oxygenate the water. Depending on your setup oxygenating the water is required, not doing it will ultimately kill the plant.

4. How To Prevent Root Rot?

Preventing root rot is relatively easy. By solely providing an optimal medium for them to grow, you will prevent any possible problems they can have.

An optimal medium for roots to grow means providing the proper temperature, humidity, water, oxygen, and size of the pot.

If you take care of these, there won’t be a problem. If you failed to provide these and your plants are already suffering from root rot, there’s not much you can do.

5. How To Treat Root Rot?

The first step to treat root rot is to identify what is causing it, as said above, root rot is caused by not providing an optimal environment for your roots.

Because root rot is caused by different organisms, a solution that works for some growers may not work for others.

You should start by checking the environmental factors, such as humidity, temperature, watering frequency, and drainage of the medium. Adjusting the environment is more of a long-term solution, after you adjusted whatever was wrong with it, it’s time to combat the root rot with a short-term solution.

To combat root rot immediately, some growers use a mix with 100ml of bleach or hydrogen peroxide with 1L of water.

Using hydrogen peroxide will kill the organisms causing root rot but can be bad if you’re growing organically because it can kill good bacterias too. In such low concentrations, bleach shouldn’t be harmful but this is a cheaper alternative and may be harmful to the bacterias in some cases.

The best way to treat root rot if you are willing to send a little bit more is to use root supplements. This products are mixed into the water and provide everything a root need to grow healthy and also combat root rot. There are a variety of root supplements out there and the one you choose should be based on what you can afford and what will work in your case.

5. In Conclusion

Root rot is a really serious condition, most experienced growers opt to remove the plant from the growing space in fear the condition can infect the other plants, especially in hydroponic setups.

When dealing with this condition, the best thing to do is to maintain an optimal environment for your plant and roots because you’ll only notice something’s wrong after a couple of weeks when the conditions start to affect your plant’s leaves and branches, and at this stage, it is very hard to treat it, and even if you manage to save your plant, it will be left with serious growing deficiencies.

Cannabis root problems are usually called as root rot. Problems in the roots can be caused by different organisms such as bacterias, fungi, and parasites and al

Root Problems

Table of Contents

Cannabis Plants With Root Problems Show Many Symptoms

  • Cannabis may appear overwatered or droopy
  • Curling or cupping of leaves
  • Wilting – either individual stems wilt or the whole plant may wilt
  • Slow growth, or staying very small for weeks
  • Leaf yellowing, or sometimes even other colors like purple or red
  • Brown spots / Burnt spots
  • Other strange nutrient problems
  • Brown or slimy roots – this is often a sign of root rot
  • Smelly runoff water (smells rotting or musty)
  • Leaves may start dying and falling off rapidly
  • Plants drink much less water than usual

Example of extreme overwatering on an adult cannabis plant

This seedling was being grown in pure perlite, which is not a suitable growing medium for cannabis, and as a result the roots were not getting the proper levels of air and water. This seedling needs to be transplanted to soil or coco (or even into hydro) in order to get better.

This clone was give the same amount of water from when it first sprouted. As the plant started getting bigger and drinking more, this wasn’t enough and became chronically underwatered (a different type of root problem, with similar symptoms). What this particular plant needed was to be given more water at a time. One warning flag was that the plant was drying out every day (you should only have to water your plant every few days, if it’s drying out in just one it likely needs more water at a time). It’s always a good idea to listen to your plants when deciding when to water, as opposed to following a set schedule. Each plant and environment is different, and what works for some plants may not work as well for others!

The cannabis plant below did not have any drainage holes (water could not drain out the bottom of the pot). Notice the strange twisting of some of the leaves. When roots are left in stagnant water for too long, they cannt get enough oxygen and tend to develop root problems.

More overwatered marijuana seedlings – these were overwatered since theyf first germinated. If leaves are drooping down in normal heat, but still seem kind of “fat” it’s often something with watering or roots!

Example of a cannabis seedling with what appears to be a nutrient deficiency, but the symptoms are actually caused by overwatering / root problems

This particular type of cupping of the leaves below is common among cannabis plants with root problems. In this case, the plant had no drainage from the bottom of the solo cup, so water was just pooling at the bottom for the roots to sit in. Once the grower poked holes in the bottom of the cup, this problems went away (the cupped leaves didn’t recover, but new leaves started growing in happy and healthy).

Sometimes leaves will tend to cup or curl down due to root problems, like the plant above, but sometimes the curl upwards too, like the poor plant below (this was caused by poor drainage and plant was overwatered, leading to a pretty severe case of root problems):

This next plant was also overwatered and had no drainage. Notice how dark the soil is and the green algae growing all along the top of the soil – these are more signs the plant has been overwatered for quite a while. You should never water your plant when the soil is still wet at the top, and if you notice lots of algae growing on top of your soil, it may be a sign that you’re overwatering on a regular basis.

The grower went away for a few days, so they chose to overwater their plant in hopes it would be enough water until they got back. While they were gone, they had a huge heat wave. So this plant was subjected to overwatering plus heat. A few days later, when the grower came back, they saw that the leaves were cuppping upwards and had turned lime green. The stems and veins of the leaves were turning red. You can see the soil is still dark and wet because the plant stopped drinking after developing root problems.

Another plant from that same batch which reacted differently

Chronic overwatering in thick soil led to these symptoms. The main thing that alerts you to the fact that the yellowing is caused by overwatering is the fact that it’s droopy. It’s very easy to overwater young plants when you have a small seedling in a big container. When that’s the case, don’t soak the whole growing medium. Water in just a circle around the plant until its leaves are up and growing fast. At that point you can start watering more thoroughly 🙂

The following seedling is almost a month old, but it’s been overwatered its whole life. As a result, it’s stunted and small. The biggest hint that the roots are at fault is the fat, droopy leaves. The fact that it’s a small plant in a big container also makes it more likely for plants to develop root problems.

The strange yellow and red growth in this picture has been caused by giving the plant too much water, too often. Overwatering can often causes what appears to be nutrient deficencies in young plants! Older plants tend to just droop, but especially seedlings can have really odd reactions to overwatering.

The plants below developed root rot in a hydroponic setup. This is usually triggered when the roots can’t get enough oxygen, usually due to high temps or poor oxidation of the water. Notice the strange burnt appears on some of the bottom leaves. They turned almost white. The whole plant was drooping, especially towards the bottom. The roots turned brown (pictures below).

The plant on the right is healthy, and the plant on the left has root rot. It’s interesting how the symptoms from root problems are often similar, whether the problem is in soil or hydro!

More side effects of root rot

Root rot! No wonder the leaves were having so much trouble on top.

Possible Triggers For Root Problems

  • Heat – cannabis is more likely to have root problems at higher temperatures
  • Cold – cold roots are unhappy roots – cold shock can cause wilting and other problems
  • Over-watering potted plants – too much watering tends to cause root problems
  • No drainage hole at the bottom of the container – if water can’t get out and water is sitting at the bottom of the pot, the roots can “drown”
  • Muddy or thick soil – if your soil is muddy and thick instead of rich and fluffy, it may mean the soil doesn’t hold enough oxygen to support your roots.
  • Small plant in a big container – When a seedling (or small plant) is in a big container, it often has trouble getting enough oxygen at the roots. Until the plant has grown bigger and started to fill up the container, it’s important to avoid overwatering. It can help to water just a little bit at a time, in a circle around the seedling, until it starts growing faster.
  • Plant has “overgrown” it’s container (become rootbound) – The roots of a rootbound plant have started circling the outside of the container, causing watering and nutrient problems even if you’re doing everything right. When this happens, you may need to transplant to a bigger container to stop the plant from being “choked” by the roots.
  • Big plant in a small container – any time you have a big plant in a small container, even if the plant isn’t root bound, you increase the chance of underwatering since the plant quickly drinks up all the water in the soil!
  • Hydroponics – Root problems are caused when there’s not enough oxygen in the water, usually caused because it’s either too hot or there isn’t enough bubbles/aeration

Certain strains are more prone to root problems than others, but good root practices will allow every plant to thrive!

How to Treat Root Problems:

Step 1: Identify what may have caused the root problem (refer to list of possible triggers above)

Step 2: Address this underlying issue

  • Happy temps – Make sure your grow area maintains a comfortable room temperature during the day, and is a few degrees cooler at night. Learn more about how temperature affects your cannabis plants.
  • Only water your plants when they need it. How often should I water my potted cannabis plants?
  • Make sure potted plants have plenty of drainage, and there must be drainage holes at the bottom. If soil or growing medium holds a lot of water, consider mixing in 1/3 to 1/2 extra perlite to “loosen things up” and improve drainage at the roots.
  • Put plants in the right sized container to give the roots the best environment to spread out and grow. You may need to transplant to a bigger container if your plant has gotten too big or its roots are rootbound.
  • Brown, smelly roots? Learn how to get rid of root rot

Step 3: (Optional) Provide your plant with a beneficial bacteria like Hydroguard to help roots recover quickly (more info about root supplements below). Hydroguard will help fight root rot by creating a colony of good organisms to outcompete the root rot.

You May Not Want to Use Hydrogen Peroxide (H2O2) for Root Problems! H2O2 is temporarily effective at best when it comes to root problems. By it’s nature, even commercial grade H2O2 will be completely gone from a water reservoir after about 24 hours as it reacts with the water to form oxygen (decomposes) until the H2O2 is completely gone.

If H2O2 is added to a water source, it kills most of the bacteria in the water, including any good bacteria, but will not usually be able to kill all bacteria, so some bad bacteria will still be left to repopulate. Because of it’s nature, hydrogen peroxide does absolutely nothing to fix the underlying issue that causes root problems, and it kills any postive bacteria in your soil or water so sometimes it can actually make things worse. I think of H2O2 as a temporary bandaid.

I personally recommend using a supplement called Botanicare Hydroguard for root problems because I’ve used it successfully to get rid of a terrible case of Root Rot

Note: Botanicare used to have an awesome root innoculant called Aquashield, but in our tests Hydroguard works even better to create healthier roots and get rid of root rot!

Hydroguard is also much cheaper than most other similar root treatments and is proven to work well at supporting root health in cannabis. Take a look at our root rot page to see pictures of how Hydroguard was able to completely cure a terrible case of root rot.

Other examples of beneficial root supplements include Piranha, VooDoo Juice, Great White (Great White has great reviews, yet is obscenely expensive), Subculture B, Rooters, and Plant Savers. Most of these can be used with both hydro and soil grows. I personally recommend Hydroguard because I’ve used it successfully to treat Root Rot (and it’s also very affordably priced, you can use it throughout your grow without breaking the bank).

One important thing to note is that after you treat the cause of root problems, the old damaged leaves may never recover! With recovery, you should be looking for the problem to stop spreading, and for new leaves to be growing in green and healthy.

Root problems can cause wilting, drooping, nutrient issues, spots & other strange symptoms. Learn the common root problems and how to treat & prevent them.