Root rot is a common and serious plant disease where the roots decay due to an overabundance of water and a lack of oxygen in the potting medium. When soil remains saturated for too long, air pockets disappear, creating an anaerobic environment. This oxygen-deprived state causes the roots to drown, making them highly susceptible to harmful soil-borne pathogens like the water molds Pythium and Phytophthora. Once the root system is compromised, the plant can no longer absorb water and nutrients properly, leading to rapid decline.
Visual Clues Above the Soil Line
The initial signs of root rot are often misleading because they mimic symptoms of underwatering or nutrient deficiencies. A common symptom is persistent wilting or drooping foliage, even immediately after the plant has been watered. This wilting occurs because the damaged roots cannot transport water effectively to the leaves, regardless of the soil moisture level.
Changes in leaf color are another major indicator that the roots are struggling underground. Leaves frequently turn yellow (chlorosis) or sometimes a dark reddish-brown color. These color changes usually begin on the oldest, lowest leaves and gradually spread upward.
A plant suffering from root rot will also exhibit a general decline in vigor, showing stunted or significantly slowed growth. The plant may begin to shed leaves quickly, which turn brown and fall off after yellowing. In advanced stages, the rot can sometimes spread up to the soil line, causing the stem or base of the plant to become soft and mushy.
Performing the Root Confirmation Check
The only definitive way to confirm root rot is by physically inspecting the root system. Safely remove the plant from its container by tipping the pot sideways and gently easing the plant out while supporting the base. Once unpotted, gently shake off the loose soil to expose the roots for examination.
Healthy roots are typically firm to the touch and light in color, appearing white or sometimes tan. Rotted roots, in contrast, appear dark brown or black and have a distinctly soft, mushy, or slimy texture. When severely rotted, the outer layer of the root (the cortex) may easily pull away, leaving behind a thin, stringy core.
A strong, unpleasant smell emanating from the soil or the exposed roots is a major diagnostic clue. This foul odor is often sulfurous, like rotten eggs or sewage, and is produced by anaerobic bacteria thriving in waterlogged conditions. You should also check the condition of the soil, as a waterlogged or perpetually soggy medium strongly indicates conditions that favor root rot.
Essential Actions Once Root Rot is Confirmed
Once the diagnosis is confirmed, immediate action is necessary to save the plant. First, wash away all remaining soil from the roots using lukewarm running water to remove any potentially infected medium. Next, use sterilized scissors or pruning shears to systematically remove all the damaged root material.
You must cut away every root that is dark, mushy, or black, preserving only the firm, light-colored tissue. If a significant portion of the root mass is removed, also prune some foliage above ground to reduce the demand on the weakened root system. The remaining healthy roots should then be repotted into a clean container with fresh, well-draining soil.
If you plan to reuse the old pot, it must first be thoroughly disinfected using a bleach or hydrogen peroxide solution to kill lingering fungal spores. After repotting, hold off on watering for several days to allow the trimmed roots to recover and ensure the new soil is not immediately saturated. This period of dryness is necessary for the plant to establish itself in the new environment.