Root rot is a destructive condition where a plant’s roots decay, typically triggered by prolonged exposure to over-saturated soil. This environment starves the roots of the oxygen they need, making them vulnerable to fungal or bacterial infections. Pathogens like Pythium and Phytophthora thrive in waterlogged soil, attacking the weakened root tissues. If the problem is not addressed quickly, the decay spreads rapidly through the root system, eventually killing the entire plant.
Warning Signs Above Ground
The initial symptoms of root rot are often misleading because they mimic a plant suffering from drought. The plant may appear to be wilting, even though the soil is still wet to the touch. This paradoxical wilting happens because the damaged roots can no longer absorb water and nutrients effectively.
Another common sign is the discoloration of the foliage, known as chlorosis or necrosis. Leaves begin to turn yellow or brown, often starting with the older leaves closer to the base. Plant growth will also become stunted because the compromised root system cannot support new development. In advanced cases, the stem near the soil line may become soft, mushy, or discolored, indicating the rot has spread upward.
The Definitive Root Check
Confirming root rot requires a physical inspection of the root ball, which must be carefully removed from its pot. Healthy roots should look firm, pliable, and typically appear white or light tan. Gently shaking off the excess soil or rinsing the roots allows for a clearer examination of their condition.
Rotted roots will look dramatically different, appearing dark brown or black instead of their healthy color. When touched, they will feel soft, mushy, or slimy, and they may easily fall apart. The most telling sign of advanced root rot is a foul, sulfur-like odor emanating from the roots and the soil. This unpleasant smell is a direct result of anaerobic decomposition caused by microbial activity in the waterlogged soil.
Common Causes of Root Rot
The cause of this condition is nearly always an environment where roots are deprived of oxygen, most often created by chronic overwatering. When a plant is watered too frequently, the soil pores remain filled with water, pushing out the air pockets roots require for respiration. This lack of oxygen causes the root tissue to die, creating an entry point for opportunistic pathogens.
Poor drainage is a significant contributing factor, whether due to a dense potting mix or a container without adequate drainage holes. Soil that retains too much moisture creates the anaerobic conditions that favor fungal growth. Using a pot that is too large for the plant can also slow down the drying process, keeping the root environment overly moist.
Steps for Treating Infected Plants
Once root rot is confirmed, immediate action is necessary to save the plant, beginning with the removal of the infected tissue. All dark, soft, or mushy roots must be pruned away using sterilized scissors or shears. Cutting into the remaining healthy, firm root tissue ensures all decaying matter is removed and prevents the spread of pathogens.
After trimming, the remaining healthy roots should be thoroughly washed to remove lingering infected soil particles. The plant must then be repotted into fresh, well-draining potting mix in a clean container. If the original container is reused, it should be disinfected with a bleach or hydrogen peroxide solution to eliminate any remaining fungal spores. In severe cases, pruning back some of the foliage can help reduce the water demand on the weakened root system.