Understanding and Overcoming Root Rot


What is Root Rot:

Root rot is probably the most common issue associated with hydroponic gardens, and almost all of us will experience root rot with our plants at some point.  Most commonly, root rot is associated with overwatering your plants, such that they do not get enough oxygen.  This is surprising to many, but dissolved oxygen is very important for our plant roots. 

More specifically, the direct cause of root rot is one or more bacteria and fungi.  These bacteria and fungi can travel through the air, and they’re terrific at hibernating for long periods of time, which is why root rot is so common.  They also love wet environments and are able to feed on plant roots that are deprived of oxygen from overwatering.

What Does Root Rot Look Like:

Root Rot is yucky stuff.  It will turn your roots dark brown or black, but that’s not the only symptom.  Nutrient staining and age can also lead to dark roots, and it doesn’t mean you have root rot.  The #1 sign of root rot, in addition to brown or black roots, is that they become quite slimy and sometimes smelly.  When bad enough, the same fungus-like actor that causes root rot can cause dark brown and black spots on your plant leaves as well.  If you have root rot, you’re also likely to notice a significant slowdown in your plants growth.

Early Signs of Root Rot

Early Signs of Root Rot in Some Dark, Slimy Roots

How to Prevent and Control Root Rot:

It is possible for root rot to become so bad that replacing the plant is best.  This is especially true of shorter-lived plants like lettuce, that will probably need to be replaced in a few months anyway.  But, simply getting rid of a plant will not prevent root rot from coming back.  Preventing and then controlling root rot when it is present is generally your best solution.  Here are some steps you can take to prevent and control root rot.

  1. Add Beneficial Bacteria to Your Nutrient Solution - The easiest way to both prevent and control root rot is to add beneficial bacteria to your nutrient solution. Beneficial bacteria, like those in Hydroguard, are known to go to battle with the oomycetes that create root rot, so that you don’t have to.  This step is usually enough to keep your plant roots happy and healthy, but you’re welcome to read on if you’d like.
  2. Adding Hydrogen Peroxide to Your Nutrient Solution – Hydrogen peroxide can help to oxygenate and separate roots to prevent root rot. However, Hydrogen peroxide also kills both good and bad bacteria, so it’s probably not your best solution while also using beneficial bacteria.
  3. Make Sure Your Plants Are Getting Enough Oxygen:
    1. Add an Air Pump to Your Reservoir – For Aeroponic and drip systems, this isn’t necessary. Your plants are oxygenated by the air directly.  But, for systems that have roots growing directly in the reservoir, an air stone or air pump will help to keep them oxygenated.
    2. Reduce Your Watering Schedule – For systems that have roots growing directly in a reservoir of water at all times, this won’t matter. But for aeroponic systems, drip systems and ebb and flow systems, make sure you are not overwatering your plants, and that your roots have access to the oxygen they need.
  4. Keep Your Plants Healthy – Having your plants grow with the right nutrient, pH, light and temperature levels will help to keep them strong, and will prevent diseases and infections.
  5. Keep Your Reservoir Cool – Warm water holds less oxygen than cool water. If your plants are not in a well-conditioned space, they are probably more likely to have root rot during the summer.  Consider freezing soda bottles filled with water, and using them to help keep your reservoir cool on days when the temperature exceeds 85 degrees.
  6. Use Clean Equipment – It’s easy to add nasty bacteria, fungus and algae to your hydroponic system if you fill it using old buckets or tools that have been laying around. The spores can lay in hiding for months or years, only to sprout to life when mixed with the water and nutrients in your hydroponic reservoir.
  7. Reduce Light Exposure on Roots – Keeping your roots in the dark helps reduce the occurrence of algae, fungi, and other stuff we don’t like very much. And roots are not big fans of the light to begin with.
  8. Do Not Overuse Hydrogen Peroxide – Hydrogen Peroxide will kill both the good and the bad bacteria, which hurts the balance of your nutrient solution ecosystem.


Root rot is one of those issues that almost every hydroponic grower will deal with at some point or another.  Adding and keeping beneficial bacterial in your hydroponic system is one of the best ways to reduce the occurrence of root rot, but there are other techniques as well.

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