How to Spot & Treat Root Rot on Plants Growing in Water

Root rot sucks. Left untreated, it can damage or kill a plant, and nearly any plant is susceptible to it to some degree. That goes for plants growing in soil, water, or leca. The simplest way to think about root rot is that it is your plant rotting, starting with a single root but potentially spreading to others and ultimately your plant rotting as well. It’s pretty nasty to witness but also easy to catch early signs if you’re paying attention, especially if you’re growing in water. 


One of the benefits of growing plants in water is that there is easy visual access to your plant’s root system. This comes in very handy in catching root rot before the plant begins showing other signs of stress. Additionally, plants growing directly in water make the removal of any roots experiencing root rot much easier because there is no disruption to the other roots which happen when growing in soil or leca. This way, you can stay diligent about maintaining your healthy plants. Read on to learn more about how to spot and treat root rot.

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WHAT IS ROOT ROT?

As a fellow plant parent, I believe I’m speaking for all of us when I say, root rot is a pesky menace to all plant parents! Deadly but treatable, root rot is a disease that attacks a plant’s root system, causing them to decay. The roots will be the first thing to rot because they are sitting in water--and signs will show up in the plants’ leaves soon after. Later stages of root rot express themselves as leaves being wilted and discolored. If left untreated, root rot will make it very difficult (and almost impossible) to bring your plant back to normal health.


Something similar to root rot can happen in the propagation process with plants that haven’t rooted yet. If the cutting is slow to propagate, extended time in water can cause some parts of the plant to begin to rot as well, similar to root rot. You’ll most often see this happening on a stem section beyond the last node, and that is why we recommend taking cuttings just below the node.


Here's a video of our team removing a root-rotted stem from a Siltepecana that's growing in water. 


Signs of Root Rot

1. yellow or wilting leaves

Not all yellow or wilting leaves mean root rot - often times a yellowing leaf is just a natural part of growth - but it does warrant a quick inspection. Most plants don’t show stress from root rot in their leaves until it’s been there for a while - so if root rot is the problem here, we recommend acting quickly. 

2. Black or brown mushy roots

An early sign of this is discolored water, usually grey or brown. Anytime clean water begins to color like this, it’s great to take a moment to check out the root system to make sure nothing is wrong.

3. A ROTTEN SMELL

This is more of the case for root rot showing up in plants growing in water or leca. If you’re getting an astringent or funky smell for your plant, check those roots out immediately. 


What Causes Root Rot?

1. TEMPERATURE EXTREMES

Every plant has a different high and low-temperature range, but extremes on either end can trigger rotting roots. Plants growing in water can be more susceptible to this because water more efficiently conducts temperatures directly to the roots. On the other end of this, soil acts as a buffer to somewhat protect the plant from more extreme temperatures.

2. LACK OF OXYGEN IN THE WATER

For a bit of review on the basics of plants, plants use oxygen and energy from the sun to then create nutrients to grow. Plants that grow in water absorb oxygen from the water, whereas regular soil plants get their oxygen from the soil. So, it is crucial to refill the water in your planters regularly to oxygenize the water and avoid root rot. 


Leaving plants in water that hasn’t been replaced for weeks or months depletes the oxygen in the water, which is needed by plant roots for growth. In some cases, these oxygen-starved roots can effectively suffocate and die, leading to root rot. This is effectively the equivalent of forgetting to water a plant that’s in soil - just the opposite outcome of rotting instead of drying out. 


One trick to reduce the dependency of a plant on its water being replaced is to use leca as the growing medium. Gaps between leca hold oxygen which can be absorbed by the roots, reducing their dependency on oxygen in the water. Just monitor water level and you’ll be set!

3. BENT OR BROKEN ROOTS

It’s always worth being careful when handling a plant’s root system. Repotting and trimming roots can cause a shock to the plant system. Similarly, if a root gets bent too hard or too far, even without breaking, can lead to structural damage and ultimately a rotting root. Be careful, roots are delicate. 

4. IN SOIL, OVERWATERING

A bonus section here for those growing plants in the soil as well. The age-old challenge of plant parenting is, how often do I need to water my plant? And if that answer to that is over-watering, then one of the early cooperates to an unhealthy plant is root rot. 


How to Treat Root Rot

Root rot can be easily treated by following these three simple steps: 


Step 1: Remove Rotting Roots

Cut off any diseased roots using a sterile cutting tool like a knife or scissors. You want to make sure that you’re cutting off the roots that are black and mushy. 


Step 2: Soak in Hydrogen Peroxide Bath

After you’ve cut off any dead roots, we recommend soaking them in an 80:20 solution of water to hydrogen peroxide. Five minutes or so should be sufficient.


Step 3: Replace Water

Lastly, you’ll want to clean your MOBO planter and replace the old water with fresh filtered water. Carefully put your plant back into the planter by guiding the roots with your hands to avoid disrupting the root system. 


How to Prevent Root Rot

If the cause is cold temperatures, figure out an area in your space like away from a window where your plant would receive more stable temperatures. If the cause is a lack of oxygen, continue to refill the water every week and replacing the water every 2-4 weeks.  


Now that you’ve learned more about how to treat root rot, you’re one step closer to being the ultimate plant parent. For more information about your particular plant, check out our plant resource library on the Modern Botanical website. 


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