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Root Rot

Cannabis Root Rot – Slimy brown roots are caused by pathogens you don’t want in your hydro tank

The marijuana plant on the left is healthy, and the plant on the right has root rot.

Example of the effects of root rot on a cannabis plant

What cannabis root rot looks like “under the hood”

These cannabis roots are brown with root rot - they're slimy, smelly, and will kill your plant if not treated immediately!

Root rot can be caused by several different organisms including types of bacteria, fungi and parasitic oomycotes. Although the symptoms are similar between different types, they don’t always look exactly the same. However, growers generally refer to all types of unhealthy root browning as just “root rot.”

But because cannabis root rot can be caused by different pathogens, a solution that solves the symptoms for one grower may not necessarily work for another grower. That being said, there are ways to fight against root rot no matter what kind you have!

Some types of root rot affect the roots below the surface of the water

Cannabis roots just got root rot - brown roots and leaves are wilting - often triggered by heat

And sometimes it’s only the roots above the surface of the water that turn brown, while the roots in the water stay white

Sometimes it's only the roots above the water that are being affected, and the roots in the water itself are still relatively healthy

The first sign of root rot is usually wilting or drooping, and root rot often strikes immediately after a reservoir change, especially for young plants. If this happens to you it’s recommended to only top off your reservoir for the first several weeks, and wait to do the first full reservoir change until after the roots are well established. This allows young roots time to build up a biofilm that protects them against root rot during reservoir changes. Learn how to care for hydroponic seedlings.

Example of the clawing, curling leaves caused by cannabis root rot (root problems)

Cannabis root rot can cause leaf symptoms that can look like almost anything: cannabis leaves get burnt edges or tips; yellow / bronze / brown spots or stripes; nutrient deficiencies; clawing and curled edges; and other unusual leaf symptoms.

Example of a sick cannabis leaf caused by root rot

Root rot can cause curling leaves and brown or burnt patches

The burnt discolored leaves of a cannabis plant with root rot

Cannabis roots with root rot often look slimy (though not always), in fact sometimes it almost looks like they have snot on them 🙁

Slimy, snotty cannabis roots with a bad case of root rot and possibly an algae bloom

Important: The Following Roots Are Stained From Nutrients – They Are NOT Brown From Root Rot

Nutrient-stained roots are not slimy or smelly and all the roots are evenly dyed the same color. You’ll be able to see each individual “strand” on healthy cannabis roots. You also won’t see leaf symptoms or wilting on the plant itself.

What To Do About Marijuana Root Rot & Root Slime

Problem: Your cannabis plant starts drooping, leaves start getting sick, and roots are brown, smelly and/or slimy. These are all symptoms of cannabis root rot.

These cannabis roots are brown with root rot. Sick roots often look wound up or twisted like this, and the individual "strands" sort of meld together with slimeRoots need water, but if they are get water without enough oxygen they are much more susceptible to root rot. This is often caused by too-hot conditions, overwatering, and/or not enough bubbles dissolving oxygen into a DWC water reservoir.

However, root rot is caused by many different types of organisms, and even if you create a great environment it can strike if you don’t take precautions.

Healthy roots are white to cream-colored while roots affected by root rot are brownish, often slimy and may smell like mildew or even rotting.

The very first sign of root rot in cannabis (besides brown roots) is usually wilting or drooping. Plants affected by root rot may spontaneously start getting sick, with leaves becoming yellow or bronze. The cannabis plant itself starts drooping, wilting, or otherwise looking like it’s dying.

Sometimes the plant will not wilt, or will recover from wilting while still showing other signs of root rot. This is your plant powering through, though you still want to take care of the problem before it gets worse. Although wilting is common, you cannot be sure your plant doesn’t have root rot just because it’s not wilting. It’s much more important to look at the roots in order to accurately diagnose root rot.

The first sign of root rot in hydro cannabis plants (besides brown roots) is usually wilting

The wilting is often soon be followed by other symptoms to the leaves, especially burning, brown spots, nutrient deficiencies, spotting, and other unusual leaf symptoms.

The burnt discolored leaves of a cannabis plant with root rot

This is an example of what cannabis leaves can look like after the plant starts suffering from cannabis root rot

You will also notice that affected plants will start drinking less water. If you notice these symptoms in your cannabis plant, then it can’t hurt to try all the suggestions for stopping root rot.

A cannabis plant affected by root rot - leaves are turning brown, discolored, burnt white tips and edges, curlingA cannabis plant affected by root rot - leaves have spots, burnt yellow tips and edges, curling

It’s important to notes that damage is permanent to both the roots and the leaves.

Old brown roots will never turn white again. Brown leaves will never turn green again. You need to insteaed be looking at new growth for signs of root rot recovery.

A recovering plant will be able to make new growth, but its old infected roots will likely never recover. Instead, you know that recovery is happening when new white roots start growing from the old brown ones.

Root rot mostly affects hydroponic systems, but can also result from over watering your plants in soil or other medium. Basically anytime the roots are sitting in wet conditions for too long, they are at risk of devloping root rot.

  • Plants may appear overwatered or droopy, sometimes plants wilt overnight
  • Brown, slimy or smelly roots
  • Plant leaves often start turning yellow or white
  • Leaves may start dying and falling off rapidly
  • Oftentime you’ll see what appears to be a random mix of nutrient deficiencies on the leaves – this is due to the fact that the plant can’t absorb nutrients properly at the roots even if they’re there
  • Plants drink much less water than usual

A gross, slimey case of brown roots - caused by a pathogen known as "root rot." Yuck!

Now that you know what root rot looks like, it’s time for the cannabis root rot solution!


It can be tough to get rid of root rot and many people feel it’s easier to just scrap the plant and start over. However, if you’re growing in the same spot you’re likely to get it again, and there are proven techniques that will cure your plant of root rot problems.

In order to get rid of root rot successfully, you need to take a two pronged approach. You will need to treat the plant’s root directly and you will also need change the plant’s environment so that root rot no longer has a good place to grow.

Go through the below list and make sure you’re covering all your bases to both get rid of root rot permanently and prevent a re-occurrence. It’s also important to note that affected roots will likely never recover, just like how discolored leaves on the plant will never recover. What you’re looking for is new, healthy white root growth coming out of the old sick roots.

Learn how to prevent and treat root rot…

1.) Add Beneficial Root Bacteria – Crucial!

Some people like to add beneficial bacteria to their water to help prevent and treat root-related plant diseases and help make nutrients available to the plant. Some of the formulas available are Hydroguard, 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 in hydro, and I’ve also seen it work for dozens (if not hundreds) of other hydroponic cannabis growers, too! Plus it’s very inexpensive and concentrated enough that a single small bottle can last throughout your grow.

Botanicare HydroGuard is a great treatment and preventative for marijuana root rot

The “secret sauce” in Hydroguard is a specific type of bacteria called Bacillus amyloliquefaciens. It survives in hydroponic reservoirs better than other types of Bacillus bacteria and fights many root ailments including different types of fungi, bacteria and oomycotes. It not only gets rid of and prevents root rot, but there’s some evidence Bacillus a. may actually help lower salt concentration in the plant tissue itself!

2.) Lots of bubbles

As I mentioned, it is incredibly beneficial to try to get as much oxygen as possible dissolved in your water. Therefore it’s a good idea to buy a BIG air pump and big air stones for your hydroponic system.

Up to a point, the more bubbles and surface agitation, the better, as this dissolves more oxygen into the water. As long as the roots are not being very disturbed, you can’t really go wrong with adding more oxygen.

Root rot cannot thrive in an oxygen-rich environment and your plants will grow faster with lots of oxygen. I use one EcoPlus 2 Air Pump w/ 2 Outlets for each 10 gallon container (which each hold 6 gallons of water), which I have connected to 2 large air stones per air pump (since this one 2 outlets – this helps make sure there’s plenty of oxygen in the water healthy roots and faster growth).

Get a large airstone on Amazon to make lots of bubbles!Get a large airstone on Amazon to make lots of bubbles!3/16" Flexible Airline Tubing for AquariumsGet a EcoPlus 728360 3W 2 Outlet Eco Air Pump, 126 GPH on!

This has worked great for me – I haven’t had root rot since I started using this air pump/air stone combination. But lots of different pumps and types of air stones will work great – the important thing is to make sure that you’re seeing lots of bubbles!

Make sure there are lots of bubbles in your plant reservoir to help protect your cannabis from root rot!

3.) Keep grow room cool

Lower the temperature of the grow space under 80°F, and even better under under 75°F.  This also lowers the temerature of the water in your reservoir. Water can’t hold much dissolved oxygen at higher temperatures and your plants need oxygen to “breathe.”

Getting more oxygen to the roots not only helps fight root rot, it makes your plants grow much faster. If it’s too hot in the grow space, you’re much more likely to run into root rot as well as overall droopiness.

In an ideal world, the maximum recommended temperature for the water in your reservoir is around 72°F (22°C) and some growers will go to great lengths to keep their reservoirs very cool. However, when using a great supplement like Hydroguard that fights root pathogens directly, you can usually keep the temperature quite a few degrees higher without as a problem.

4.) Top off reservoir for first few weeks, without doing a full reservoir change until after roots are well established.

When it comes to nutrients and plant growth in a hydroponic setup, it’s important to change your reservoir water regularly. This is especially important in the flowering stage when the plant is very sensitive to nutrients and pH. Regularly changing your water every 7-10 days will help your plants get better access to nutrients, and help prevent deficiencies and toxicities.

However, when your young seedling or clone is first getting established in your hydroponic system, it doesn’t have an established a colony of good bacteria around the roots, and has not yet grown a biofilm that protects the roots against pathogens.

During this initial period, a full reservoir change can throw everything off balance, and your roots have to sort of “start over” from the beginning.

That’s why it’s recommended for the first 3-4 weeks of your cannabis plant’s life to only top off the reservoir with additional nutrient water, and hold off on a full reservoir change until your plants have grown lots of roots with a healthy layer of biofilm over all the roots and sides/bottoms of the tank.

5.) Keep Everything Clean

In a hydroponic system, make sure that any dead roots, dead leaves or other types of plant debris doesn’t get into the reservoir because they will provide a breeding ground for bad bacteria as they start rotting. If you do notice organic matter in the reservoir, fish it out as soon as possible.

You also want to keep your grow area as clean as possible at all times to stop bacteria before it starts. Before you begin your grow, it’s a great idea to clean all grow-related items to kill any bacteria or fungus.

6.) No light to the roots

Don’t let any light get to your roots or reservoir water, as it provides heat and light which will promote the growth of algae and bacteria (and not the good kind).

Hydrogen Peroxide (H2O2) Is Only a Temperary Solution

Don't use H2O2 for cannabis root rot - it's temporarily effective at best

Some people recommend treating cannabis root rot with H2O2, also known as hydrogen peroxide. While adding hydrogen peroxide to your water will kill most bacteria and pathogens, including the ones that cause root rot, it is only effective in your system for a day or so or since the H2O2 is quickly converted to oxygen and water.

Therefore, if you use hydrogen peroxide as a treatment for root rot, you will need to treat your water daily to prevent re-occurances until you actually fix the problem that is causing your root rot in the first place. I have tried used commercial grade H2O2 before, and I was never able to use it to get rid of root rot, so this is NOT RECOMMENDED as any type of long term cure!

Why Not Use Hydrogen Peroxide? H2O2 is only temperarily effective at best when it comes to getting rid of root rot. It makes me so sad when people tell growers to use H2O2 (hydrogen peroxide) to kill root rot. Even the commercial grade stuff just doesn’t work (and I’ve tried)!

All H2O2 does is cause bubbling near the dead brown roots (or any organic matter), which is why I think people believe it’s helping. In my experience it doesn’t help the plants themselves (they don’t look any better), and what’s worse, all the H2O2 will be completely gone from the water within 24 hours.

H2O2 kills most of the bacteria in the reservoir, including any good bacteria you’ve added, and does nothing to address the underlying problem. You can’t sterilize away root rot, it attacks people everywhere! Although H2O2 does kill bad organisms, it leaves enough of it there to repopulate your reservoir. As common as the advice to use H2O2 for root rot is, I’ve never seen a case by a real grower who was actually able to get rid of root rot with H2O2.

Your plant can completely recover from root rot as long as you catch the problem early enough, so it’s important to stay vigilent of root rot during your first couple of grows, expecially when growing cannabis with hydroponics!

Botanicare HydroGuard is a great treatment and preventative for marijuana root rotI personally recommend Botanicare Hydroguard (the newer, improved version of Botanicare’s popular “Aquashield” root supplement) for marijuana root problems because I’ve used it successfully to get rid of a terrible case of Root Rot (and by ‘successful’ I mean new white roots exploded out of the old mushy brown ones and I was able to eventually harvest the buds – look at the pics below).

Hydroguard (and their old supplement Aquashield) are also much cheaper than most other similar root treatments, and in my experience more effective.

Take a look at what happens with the roots from using a supplment like Hydroguard or Aquashield.

With recovery…

What you are looking for is new healthy white roots growing out of the old brown roots. Eventually, as the root ball gets bigger, you will no longer be able to see the old brown roots. After you start noticing a recovery, some growers will snip off old dead roots, but I often don’t.

Before – Roots Just Got Root Rot

Canabis plant with root rot - hydroponics - deep water culture DWC

Cannabis roots just got root rot - brown roots and leaves are wilting - often triggered by heat

Roots are beginning to recover

Notice the new white roots growing out of the old brown dead ones within just a day or two of receiving Aquashield in the reservoir. By this point, the plant has stopped showing any new symptoms and appears to be growing normally.

This cannabis plant is beginning to recover from root rot - notice the new white roots growing out of the old sickly brown ones

Roots are now mostly recovered below

Notice that you can barely see any signs of the old brown, and all the new roots generally appear white and healthy. The plants on top are lush, healthy, and fast-growing, though the old burnt leaves never recovered.