Recognizing root rot in potted plants

A plant with root rot often looks thirsty even when its soil is wet. Wilting, yellowing and drooping leaves appear above the surface because damaged roots can no longer move water into the plant. The real trouble sits underneath, where roots have softened and begun to decay, usually after sitting in saturated soil with too little oxygen for too long.

Root rot is most common in pots without drainage, in heavy or compacted mixes, and in plants watered on a fixed schedule regardless of how dry the soil is. Soil-dwelling fungi and bacteria that thrive in wet, low-oxygen conditions attack roots that are already weakened. Catching the problem early matters, because the more healthy roots remain, the better the chance of recovery.

What root rot looks like above the soil

Above-ground signs overlap with underwatering and nutrient problems, so they are a prompt to check the roots rather than a confirmed diagnosis. Look for wilting while the soil is still wet, leaves that yellow and drop from the base, and stems that feel soft or darken at the soil line. Gently press the lower stem between your fingers: firm stems are healthy, while stems that collapse or squash easily suggest decay has reached the crown. A plant that does not recover after a correct change in watering is another warning sign.

Check the soil itself as well. Soil that stays soggy for days after watering, smells sour or musty, or sits in a pot with no drainage hole is a strong clue. Small flies hovering around a pot can appear with persistently wet soil, although they are not proof of rot on their own.

Checking the roots without damaging healthy ones

To inspect the roots, slide the plant out of its pot and loosen the root ball gently with your fingers rather than pulling on the stem. Rinse off the old mix in lukewarm water so you can see the roots clearly. Healthy roots are firm and springy, and most are white or tan. Rotted roots look brown or black, feel mushy or hollow, and slough off when touched. Some give off a sour or rotten smell.

Compare the roots from one side of the root ball to the other. Rot often starts in the zone that stayed wettest, usually near the bottom of the pot, so the roots there tend to be the most affected. Roots higher in the pot may still be firm and pale. Use that contrast to guide how much you trim.

Judge the extent before cutting. Partial rot shows up as a few brown or soft roots scattered through an otherwise white, firm root ball. Widespread rot shows up as soft, dark roots through most of the root ball, with little firm tissue left, and the plant then has far less capacity to recover. Trim the damaged roots with clean, sharp scissors, cutting back to firm tissue, and leave the healthy roots intact. Disinfect the tool with rubbing alcohol before and after use so the cut does not spread the problem to healthy tissue.

Trimming, repotting and deciding whether to save the plant

Once the rotted roots are removed, repot the plant in fresh, well-draining mix in a container with at least one drainage hole. Choose a pot only slightly larger than the root ball, since a large pot holds extra wet soil that the remaining roots cannot use. If the top growth looks large compared with the surviving roots, remove some leaves or stems to lower the demand on the roots.

Discard the old, rotted potting mix rather than reusing it, since it may hold the same pathogens. Wash the pot with hot, soapy water, or soak it in a dilute bleach solution, and let it dry before repotting. A pot without drainage holes should stay out of use until it has holes or is swapped for a container that drains.

Water lightly after repotting, then wait until the top layer of mix dries before watering again. Test it with a finger pushed about an inch into the pot, and water only when the mix feels dry at that depth. Keep the plant out of harsh sun while it recovers. A plant can often recover if some firm roots and healthy stem tissue remain, and new growth over the next few weeks is the sign that the roots are working again. If the entire root system is mushy and the stems are soft, the plant may not survive. In that case, take healthy stem tips as cuttings and root them separately so something of the plant continues.

Hold off on fertilizer while the plant recovers. Feeding a plant with damaged roots adds stress, because the roots cannot take up nutrients efficiently. Resume a light feeding schedule only once new growth is clearly emerging.

Root rot is easier to prevent than to reverse. Use a pot with drainage, a mix that drains freely and a watering routine based on the soil's moisture rather than the calendar. Clear blocked drainage holes too, since a hole plugged with old mix or roots works like no hole at all. The earlier the problem is caught, the more roots remain to recover with.