Treat root rot

Root Rot
By Bjornwireen – Own work, CC BY-SA 3.0,

Root rot is a bacterial or fungal infection of the plant’s root system. There are many causes, but you’ll find that it’s common in Kratky grows, and when DWC grows get neglected. While this will often kill the plant, there are some simple things you can do to save it, if caught early enough

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Diagnosing Root Rot

Root rot is pretty easy to diagnose in Kratky, DWC, and any hydro method that has open roots. The roots will appear dark, and that color is most present at the root tips. There is sometimes a faint, foul smell.

Mild cases may not immediately impact your plant, but eventually, your plant will start to show symptoms of nutrient deficiencies.

Treating Root Rot


Unfortunately, root rot is often fatal to the plant. Because finding it before it becomes symptomatic in the above-ground part of the plant doesn’t always happen, you may be too late to do anything about it. By this point, your plant has a large, dead root-mass, and nothing to keep it going.

Isolate the plant and clean connected systems

If you plant is in contact with other plants in the root zone, or share a closed system, you will almost certainly need to treat all the plants. Isolate and clean what you can. You want to halt the spread quickly. Cleaning and replacing nutrients decimates the rate of spread.

Root rot
This plant has seen better days

Clean the root system

For DWC, and Kratky, it’s easy enough to drain the reservoir, and wash off the roots. You may need to root around with clean hands to find pockets of dead roots. Remove them as best you can. Often, simply running the roots under running water will dislodge dead parts.

Soil-entrenched plants are not going to do well with this treatment. You may need to cut back the plant to a smaller root ball, and treat that as best you can, then re-pot the plants.

When done, you should have only white roots remaining.

Lightly disinfect the roots in hydro

In hydro (only), you can now run a regular course of hydrogen peroxide. This will sanitize the roots and add additional oxygen to the root system. This will help slow the infection from spreading. The usual concentration is 3ml of 29% H2O2 to 1 gallon of water. However, if all you have is 3%, you can use 30ml to 1 gallon. The plant should sit in this for 3 days. You can add light nutrients to the water.

Feed the plant and inoculate the grow medium with a beneficial bacteria

If you had to treat a soil plant, it’s going to need a little fertilizer with immediately available nutrients. Any compost you use must be mature and ready. Consider adding a humic acid supplement to improve the nutrient uptake of trace minerals. The fastest way is to use mineral fertilizers, or even hydroponic fertilizers at a 50% concentration.

Regardless of methodology, you should inoculate the grow medium with beneficial bacteria and fungi. Hydro grows work best with a product like Hydroguard that is purpose built to not leave a mess but will still crowd out detrimental organisms.

Soil growers have a bit more choice. I have had great success with Microbe Life’s Yield Enhancer. It does add some humic acid and has lots of microbes in it. Be aware, it smells terrible.

But if the lightly sulfurous smell of the Microbe Life product is too pleasant, Fish Shit should do the job. It’s, well, concentrated fish effluent. It’s full of beneficial bacteria, nutrients, and smells. It is absolutely NOT suited for hydro in any way.

Continue watching your plant

Continue the feedings and inoculation regime for a few weeks. If at all possible start a clone to carry on the genetics.

Preventing root rot

The keys to preventing root rot:

  • Keep reservoir temperatures low enough to stimulate runaway microbe growth. Under 70F/21C is best.
  • Inoculate your grow media with appropriate beneficial microbes
  • In hydro, prevent algae. While algae is harmless to the plant, dead algae are microbe food and can stimulate harmful microbes.
  • In Kratky, keep things clean and change your nutrient solution if you see signs of microbe growth.

4 years ago

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