What Does Root Rot Smell Like? And How to Fix It

An unpleasant smell coming from a houseplant’s pot is a primary clue that something is amiss below the soil surface. This foul odor is a common symptom of root rot, and for many plant owners, the smell is the first noticeable sign of trouble. Understanding what this specific odor indicates is the first step toward diagnosing the issue and learning how to correct the conditions that caused it.

Identifying the Smell of Root Rot

The odor of root rot is distinct and easily distinguishable from the normal scent of healthy soil. A healthy plant’s potting mix should have a fresh, earthy smell, reminiscent of a forest floor after a light rain. This pleasant smell signifies the presence of beneficial microorganisms and proper soil composition.

In contrast, the smell of root rot is foul and signals decay. The most common comparison is a musty, moldy scent, much like a damp basement or clothes left in the washing machine for too long. In more advanced stages, the odor can become sour and stagnant, similar to swamp water. As the condition worsens, the smell can intensify into a pungent odor of decomposition, sometimes described as smelling like sulfur or rotten eggs.

Why Root Rot Smells Bad

The unpleasant smell associated with root rot is a direct consequence of a change in the soil’s microbial environment. This process begins when the soil becomes waterlogged from overwatering or poor drainage, which depletes the oxygen available to the roots. This lack of oxygen creates an anaerobic environment, which is inhospitable for the plant’s roots and the beneficial aerobic microbes that reside in healthy soil.

With the beneficial organisms gone, anaerobic bacteria and fungi begin to flourish. These microorganisms thrive in oxygen-deprived conditions and feed on the dying and decaying root tissue. As part of their metabolic process, these microbes release various volatile compounds. The most notable of these are sulfur compounds, which produce the characteristic rotten-egg smell, and other gasses that contribute to the overall sour and musty odor.

Confirming Root Rot with Other Signs

While a bad smell is a strong indicator, it should be confirmed with other physical symptoms to make a confident diagnosis. Above the soil, the signs of root rot can mimic the appearance of an under-watered plant. You may notice leaves, particularly the lower ones, turning yellow or brown and dropping from the plant. The plant might also appear wilted or limp, even when the soil is moist to the touch, and overall growth may be stunted.

For a definitive confirmation, you must inspect the root system itself. Gently remove the plant from its pot and examine the roots. Healthy roots are firm, pliable, and light-colored, often white or tan. In contrast, roots affected by rot will be brown or black, feel soft and mushy to the touch, and may even fall apart or seem slimy when handled.

Addressing and Preventing Root Rot

Once root rot is confirmed, you can take steps to address the issue. Carefully remove the plant from its container and wash away as much of the old soil as possible to get a clear view of the root system. Using clean, sterile scissors or pruning shears, trim away all of the affected roots that are brown, black, and mushy. Be thorough in removing the decayed tissue, leaving only the healthy, firm roots.

After trimming the roots, discard the old, contaminated soil and repot the plant in a clean container with fresh, well-draining potting mix. To prevent recurrence, focus on proper watering habits by allowing the top layer of soil to dry out between waterings. Ensure the pot has adequate drainage holes to prevent water from pooling at the bottom. Using a well-aerated potting mix with ingredients like perlite or sand will also help maintain the necessary oxygen flow to the roots.