How to Bring a Houseplant Back From Root Rot

How to Confirm It Is Root Rot

To bring a houseplant back from root rot, slide it out of its pot, cut away every brown or black root, and repot what is left in fresh mix in a clean pot that is just large enough for the smaller root system. Then keep it in indirect light for 7 to 10 days and keep the soil from staying wet. A plant with only a few infected roots is a good candidate for rescue, and a severely infected one is not.

The telltale sign is a plant that wilts while its soil is still wet. The University of Wisconsin plant disease clinic lists the symptoms as wilting even though the soil is wet, stunted growth, and leaves that turn yellow or red. Iowa State University Extension adds the usual order: the bottom leaves wilt first, and the wilting may progress upward until the whole plant collapses.

Leaves alone do not settle it, because yellow leaves on a houseplant have several other causes. Look at the roots.

	Healthy roots	Rotted roots
Feel	Firm	Mushy or soft
Color	White	Brown, reddish or black

That contrast comes from Iowa State, Wisconsin and Maryland. Iowa State adds that a healthy root system shows numerous feeder roots, and Wisconsin that rotted roots may have a bad odor. Clemson’s Home and Garden Information Center adds one more thing to check: the stem may be girdled at or near soil level by a ring of brown or black tissue.

What Causes Root Rot

Root rot is a disease, and wet soil is what lets it take hold. Wisconsin names Pythium, Phytophthora, Rhizoctonia solani and Fusarium as the most common root rot fungi. Iowa State explains that these pathogens thrive in wet, poorly drained soils and potting mix and infect the root systems of stressed or weakened plants. Wisconsin puts it more bluntly: root rot fungi grow and reproduce best in wet soils.

That is why the usual culprits are watering habits and containers. University of Connecticut’s fact sheet says that if you suspect overwatering, the first thing to check is whether the pot has adequate drainage holes. A plant left standing in a saucer of drained water has the same problem, and Wisconsin warns against it in capital letters.

The organisms persist. Clemson notes that the fungi survive in the soil or on infected plant debris in the soil, and that their spores can spread by splashing water or by moving infested soil. Wisconsin says not to reuse potting mix from your houseplants, and University of Maryland Extension advises separating infected plants from healthy ones. If the roots turn out to be firm and the plant is only waterlogged, the milder routine in our guide to saving an overwatered houseplant is enough.

How to Save the Plant, Step by Step

1. Slide the plant out of its pot and look at the roots and the potting mix.
2. Work the old mix off the roots and discard it.
3. Trim away the brown or black roots, leaving the firm, white ones.
4. Disinfect the blades, the work surface and any clay pot you plan to reuse. Wisconsin recommends a 10% bleach solution, a detergent solution, or alcohol.
5. Repot in fresh, sterile potting mix in a clean pot with drainage holes.
6. Set the plant in indirect light and water with care while it regrows roots.

How much you trim depends on what you find. Clemson’s advice for a light case is simple: if only a few roots are infected, cut out those roots and repot the plant in sterile soil. For heavier damage, Connecticut says to trim away the brown or black roots and repot in a container just large enough to accommodate the smaller root system.

Pot size matters here. In ordinary repotting, Mississippi State University Extension recommends a new container only 1 or 2 inches larger in top diameter than the old one. After root rot the plant has fewer roots than before, so the right pot is often smaller than the one it came out of. Our guide to choosing a pot size for a houseplant covers sizing in normal repotting.

For the mix, Connecticut notes that some plants call for a more porous blend with extra perlite, composted bark or sand. Maryland’s rule for the container is to use only clean or new pots and a sterile potting medium.

When the Plant Is Too Far Gone

Some plants are past trimming. Maryland’s guidance is to throw away severely infected plants and to take stem cuttings only from healthy tissue. If every root is mushy and the stem carries a dark ring at the soil line, a cutting from a firm, green shoot higher up is the only part worth keeping.

Fungicides are not the home answer. Clemson observes that they exist but that most indoor gardeners will find they probably cost more than a new plant. The extension guides rely on lower soil moisture, clean pots and sterile mix instead.

Aftercare for the First Month

A repotted plant sulks for a while because its root system has been disturbed. Mississippi State advises placing a newly potted plant in indirect light until it recovers from the shock, which usually takes about 7 to 10 days.

Hold the fertilizer. The same guide says not to fertilize until the root system has reestablished, usually about 2 to 4 weeks.

Watering is where recoveries fail or succeed. Wisconsin’s instruction for root rot is to reduce soil moisture: give enough water to meet the plant’s needs and prevent drought stress, but do not overwater. Empty the saucer after each watering so the pot never sits in drainage water.

Preventing Root Rot From Coming Back

Stop watering by the calendar. Iowa State’s advice is to water plants based on their specific needs instead of following a watering schedule, and Connecticut suggests checking potted plants every few days to see whether they need water. Mississippi State calls touch the most accurate test: push a finger into the soil up to the middle joint and feel for moisture before you reach for the watering can.

Three other habits come straight from the extension guides. Choose a well-drained potting mix. Use containers with a drainage hole. Start each repotting with clean pots and fresh mix, since the fungi carry over in old soil and debris.

Wilting in wet soil has one look-alike. Mississippi State lists a white or yellowish crust of salt on the soil surface, and damaged roots that cause wilting leaves even when the soil is wet, among the typical signs of overfertilization and excess salts. A crust on the surface points that way. Either way, check the roots while most of them are still firm.