What is root rot?
Root rot is exactly how it sounds: it’s when the roots of a plant begin to rot. It’s a disease that’s usually caused by a fungal or bacterial infection. It can spread to the rest of the plant quickly; before you know it, you have a limp, lifeless plant on your hands. More often than not, root rot is a result of overwatering. And it may come as a surprise, but overwatering is one of the most common issues people have with houseplants–whether they know it or not.
What causes root rot?
There are two main causes of root rot:
Overwatered soil/soil with poor drainage: Too much water is the most common cause of root rot. Overwatering can prevent roots from absorbing oxygen, and these oxygen-starved roots begin to decay.
Weakened plants: Unhealthy plants are more vulnerable to diseases, like root rot.
Many different fungi can cause root rot, especially Armillaria mellea, Clitocybe tabescens, and Fusarium. Unfortunately, you can simply be unlucky by purchasing contaminated soil. By giving your plants a routine check-up, you should be able to prevent the disease or, at least, catch it in the early stages.
How to check for root rot
The main signs to look out for are: yellowing, wilting leaves, wet soil that isn’t drying, black, wet roots, quickly declining health, and stunted growth. Fungus gnats are not always a sign of root rot, but they can indicate that the soil is too moist. Remember, one or two of these symptoms isn’t a cause for concern, but if you have multiple, then perhaps it's time to inspect your plant for potential diseases.
The most reliable way of checking if your plant has root rot (as we're sure you might have guessed) is to check the roots. Healthy roots are white or tan and firm, whereas dark, soft roots that release a foul odour are unhealthy and a possible sign of root rot.
How to treat root rot
The key to treating root rot is to act fast. The earlier you can catch it, the better your chance of rescuing your beloved plant. Here is a step-by-step guide on what you can do if you find out your plant has root rot:
Look for signs of roots that are undamaged; if there are any, there's a good chance that the plant will be salvageable.
Clean the roots under running water to wash off any infected soil.
Use sterilised secateurs to cut away all infected roots.
Prune back foliage so the root system has less work to do (around one-third to one-half will do).
Dispose of the old soil and thoroughly clean the pot with a bleach and water solution.
Finally, repot the plant using a clean soil scoop in fresh, well-draining potting mix.
How to prevent root rot
Prevention is the best method to combat root rot. Of course, it can sometimes be unavoidable, for example, if a customer unknowingly purchases soil that’s already contaminated with root rot fungus–but this is uncommon. Most of the time, you have the power to prevent having to deal with this distressing disease, and here are some ways to do it:
Proper drainage: Potted plants should have good drainage holes and be potted in well-draining soil to allow the water to run through.
Water the correct amount: Overwatering is a surefire way to get root rot. Always check the soil before watering to see if the plant actually needs water (poke a finger about an inch or two into the soil, and if it’s dry, it’s safe to water). You may find that using a smaller watering can instead of a hosepipe is helpful as it prevents you from watering in large amounts.
Don't let plants sit in water for long: You can leave plants soaking in water for 15-20 minutes, preferably no longer.