Quick answer: Root rot is caused by overwatering and poor drainage, which suffocate roots and let fungi attack them. Signs include mushy black roots, yellowing leaves, and sour-smelling soil. Treat it by trimming rotten roots, repotting in fresh dry mix, and correcting watering.

What Is Root Rot?

Root rot is a condition where plant roots decay and die, usually because they sit in waterlogged soil with too little oxygen. The weakened roots are then attacked by soil fungi such as Pythium and Phytophthora. Once it sets in, the plant can no longer absorb water and nutrients properly.

What Causes Root Rot?

Overwatering

The most common cause. Constantly wet soil starves roots of oxygen and creates ideal conditions for fungal rot.

Poor Drainage

Pots without drainage holes, or heavy, compacted soil, trap water around the roots even with careful watering.

Oversized Pots

A large pot holds a lot of soil and water around small roots, keeping the mix wet for too long.

Signs and Symptoms

• Yellowing, wilting leaves despite moist soil
• Soft, brown or black roots that smell unpleasant
• Mushy stem base and stunted growth
• Soil that stays soggy and sour-smelling

Healthy roots, by contrast, are firm and white or tan.

How to Treat Root Rot

Act quickly. Remove the plant from its pot and gently wash the soil off the roots. Using clean, sterilised scissors, cut away every soft, dark, rotten root, leaving only firm healthy ones. Discard the old soggy soil.

Repot and Protect

Repot into fresh, well-draining mix in a clean pot with drainage holes. After repotting, a fungicide can help control the fungi attacking the roots, and a bio-fungicides option such as Trichoderma offers a biological way to suppress soil pathogens and support recovery.

How to Prevent Root Rot

Prevention is far easier than cure. Always use pots with drainage holes, choose a well-draining mix, and water only when the top of the soil is dry. Empty saucers after watering so plants never sit in standing water, and avoid potting small plants in oversized containers.

Can a Plant Recover From Root Rot?

Yes, if caught early and enough healthy root remains. Severe cases where the whole root system has collapsed are usually fatal, but you may still save the plant by propagating a healthy cutting.

Choosing the Right Pot and Soil

The container and mix you use are your first defence against root rot. Always pick a pot with drainage holes, and avoid going too large, since extra soil holds extra water around small roots. Terracotta pots are excellent because the porous clay lets moisture evaporate and helps the soil dry between waterings, keeping roots oxygenated and healthy.

Match the Mix to the Plant

Different plants need different drainage. Succulents and cacti need a very gritty, fast-draining mix, while leafy tropicals prefer a richer blend that still drains freely. Adding perlite, coarse sand, or bark improves airflow around the roots. A well-chosen, well-draining mix, combined with careful watering, prevents the soggy conditions that cause root rot in the first place.

Frequently Asked Questions

Can root rot spread to other plants?

The fungi can spread through shared water, tools, or soil, so isolate affected plants and clean your tools.

How do I know if roots are rotten?

Rotten roots are brown or black, soft, and smelly, while healthy roots are firm and pale.

Does cinnamon cure root rot?

Cinnamon has only mild antifungal effects and is not a reliable cure. Correcting watering and repotting matter far more.

Does overwatering always cause root rot?

Persistent overwatering in poorly drained soil is the main trigger. Good drainage and correct watering prevent it even if you occasionally water generously.

Can I reuse soil after root rot?

It is safer not to. Discard the old soggy mix and use fresh, well-draining soil to avoid carrying over harmful fungi.