Root rot is a condition where a plant's roots begin to decompose while the plant is still in its pot, caused by prolonged saturation of the growing medium that deprives roots of oxygen. Without oxygen, beneficial aerobic root function ceases and anaerobic bacteria proliferate, producing the brown, mushy, foul-smelling roots that are the hallmark of the condition. Because the roots are hidden in the compost, root rot is often diagnosed late: after the plant has already begun to visibly decline with yellowing leaves, wilting, and stem softening. Prevention is significantly easier than treatment.
What Root Rot Looks Like and How to Identify It
The most reliable way to identify root rot is to remove the plant from its pot and inspect the roots directly. Healthy roots are firm, pale (white to tan), and often slightly fuzzy with root hairs. Rotten roots are brown to black, soft or mushy to the touch, may fall away when handled, and often have an unpleasant sour or sulphurous smell. The compost around rotten roots is typically still wet and may also smell off.
Above the compost, root rot presents as: progressive yellowing of leaves starting from the bottom, wilting that does not resolve after watering (because damaged roots cannot absorb water even when it is present), softening of stems near the base, and in advanced cases, visible darkening or collapse of stem tissue at the soil line.
The Main Causes of Root Rot
Overwatering is the primary cause, but "overwatering" means the compost stays saturated for too long rather than simply watering frequently. Contributing factors include:
- Dense or compacted compost that holds water without draining effectively
- Pots without drainage holes that cannot release excess water
- Pots significantly larger than the root ball (leaving a large volume of constantly wet unused compost)
- Saucers left permanently full of water keeping the compost saturated from below
- Low light or cool temperatures reducing the plant's water uptake so the compost never dries between waterings.
The risk of root rot is therefore highest in winter, when plants grow slowly and use water very slowly, in north-facing rooms, in plastic pots with dense compost, and for plants kept in pots without drainage.
How to Treat Root Rot
If you identify root rot early, only some roots are affected, the plant can often be saved. Remove the plant from its pot, shake off all the old compost, and inspect every root. Using clean scissors or pruning snips (sterilised with rubbing alcohol), cut away all rotten roots at the point where they transition from brown-mushy to firm. Dust the cut ends with cinnamon, which has natural antifungal properties, or with a fungicide powder.
Allow the root ball to air dry for 30 to 60 minutes. Repot into fresh, free-draining compost, do not reuse the old compost, as it harbours the bacteria responsible for the rot. Use a pot that matches the remaining root mass after pruning (which may be significantly smaller than the original pot).
How to Prevent Root Rot
The most effective prevention strategies start with the basics: always use pots with drainage holes, avoid watering on a fixed schedule, and instead check the compost before you reach for the watering can. In winter especially, watering should be reduced significantly, while a free-draining mix is always preferable to a dense, moisture-retaining blend. When repotting, keep things proportionate by only moving up 2–4cm wider than the current root ball.
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The simplest and most reliable habit of all is the finger test. Before each watering, press 3–5 cm into the compost; if it still feels moist at that depth, it’s not ready. This ten-second check is one of the easiest ways to prevent overwatering and keep roots happy. For a deeper understanding of your plant’s needs, explore our houseplant A-Z care guide.
Can a Plant Recover From Root Rot?
Yes, if the rot is caught before it has progressed to the main stem. Plants with some healthy roots remaining can recover fully after treatment, though they may drop additional leaves during the recovery period as they adjust to the reduced root mass. Plants whose stem base has been affected by the rot are significantly harder to save, if the stem is compromised, the plant may not recover regardless of root treatment.
After treatment, the plant's primary need is to develop new root growth before it runs out of stored resources. Keep the compost barely moist, provide bright indirect light, and avoid fertilising until active new growth resumes.