Root Rot and Houseplants: How to Prevent and Treat Root Rot

Root rot is a general term for a potentially fatal disease that attacks a plant’s root system and can quickly spread throughout the whole plant, leading to the death of the plant. Root rot renders plant roots useless, depriving the rest of the plant of the nutrients it needs to survive.

Although root rot primarily affects a plant’s underground root structure, signs of root rot can become apparent both above and below ground.

1. 1. Wilting, yellowing leaves: Wilting or yellowing leaves are the most obvious indicator of root rot, but they may also stem from a host of other diseases and cultural problems such as malnutrition or over- or underwatering.
2. 2. Continually wet soil: If you haven’t watered your plant recently but its soil remains wet, that may be a sign that the plant is no longer absorbing moisture from the soil. Other factors that could contribute to wet soil include overwatering, seasonal weather changes, and poor drainage.
3. 3. Stunted growth: If a formerly healthy plant suddenly stops growing, root rot could be to blame. Keep in mind that many plants’ growth slows during the winter. It’s also possible that your plant is not getting enough sunlight, or that it has outgrown its pot.
4. 4. Mushy, black roots: If your plant shows any of the above symptoms, and you’ve ruled out other potential causes, it’s time to check the roots. Healthy roots are firm and often (but not necessarily) white in color. In plants suffering from root rot, the roots turn dark and soft and may give off a foul odor.

Root rot has two main causes: lack of oxygen and fungal infection.

1. 1. Lack of oxygen: If a plant has been overwatered, has poor drainage, or its soil is too densely packed, this can cause a lack of oxygen. In these cases, the roots are essentially drowning. Without access to oxygen, they can’t do their job to sustain the plant, and the plant dies. Root rot is particularly prevalent among houseplants and indoor plants rather than garden plants, since indoor plants are more susceptible to overwatering.
2. 2. Fungal infection: Excess moisture can also provide the right conditions for a fungal infection that attacks the roots. The fungus in question may have made its way into the soil through contact with contaminated gardening equipment (like shears and pots) or may have been present in the soil when you bought it. Any number of fungi can be responsible for root rot, including Pythium spp., Phytophthora spp., Fusarium spp., and Rhizoctonia solani.

The earlier root rot can be identified, the better the odds are that you’ll be able to save the affected plants. Follow this method if you suspect your plant is suffering from root rot.

1. 1. Identify the root rot. Don’t assume your plant has root rot just because it’s wilting. Instead, carefully remove it from its soil and inspect the roots to get a clear picture of its health.
2. 2. Clean the roots under running water. Remove as much soil from the roots as possible, since the soil may be infected with fungi.
3. 3. Remove affected areas. Using clean equipment, prune away any dark or mushy roots. Be aggressive, since root rot can spread again if left untreated. If you’re left with very little root system after you’ve pruned, cut away some of the plant’s leaves so that the remaining roots have less growth to support.
4. 4. Discard the soil. Even if you’re not positive that the root rot is the result of a fungal infection, you should dispose of the potting soil. If there’s a chance that the soil contains spores, it’s not worth the risk of keeping it.
5. 5. Wash the pot and your equipment thoroughly. Clean both your equipment and the plant’s container with rubbing alcohol or a solution of nine parts water to one part bleach. This will prevent the spread of fungal spores.
6. 6. Repot the plant in fresh soil. To prevent future instances of root rot, gently separate the remaining roots and envelop them completely in a well-draining potting mix suited to your particular plant. Rather than using dirt from the backyard, use a potting mix designed for container plants, which will contain a mix of lightweight materials to keep the soil from compacting.

Sometimes root rot is unavoidable, like if you unknowingly purchased soil that happened to contain fungal spores. Fortunately, there are many instances in which root rot is entirely preventable.

1. 1. Use new potting soil. If you’ve gone through the ordeal of rescuing a plant from root rot, the last thing you want to do is reintroduce a possible cause of the problem. Dump any potentially contaminated soil, and purchase new potting mix as needed.
2. 2. Water as needed. Instead of watering your plants every day, make a habit of testing the soil around your plants’ roots. Stick a finger into the soil. If it’s still moist up to your second knuckle, your plant doesn’t need water.
3. 3. Use fertilizer sparingly. Too much fertilizer can actually weaken your plant by adding too much salt to the soil. If your plant is recovering from root rot, be conservative with your fertilizer application.
4. 4. Skip the rocks. You may have heard that placing rocks at the bottom of your pot can help with drainage, but rocks and stones can actually block drainage. Instead of adding rocks to your pot, choose a pot with adequate drainage holes, empty the pot’s saucer regularly, and purchase high-quality potting soil.
5. 5. Be careful with chemical treatments and fungicides. Unless you’re absolutely sure of your plant’s root rot diagnosis and the type of fungus that’s attacking its roots, avoid harsh chemicals or fungicides, as they might not be the right tools for the job.

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