Houseplant Root Rot 101: Symptoms, Causes, and Easy Fixes

Does your houseplant keep wilting, no matter how much you water it? Chances are you've fallen victim to one of the most common houseplant issues out there, and it's not going to be fixed with more watering.

What you're probably dealing with is root rot, a houseplant problem which is exactly what it sounds like. The plant's roots are surrounded by too much moisture, and they literally start to rot in place. It's a biological response to specific environmental stressors – usually overwatering.

Below we'll cover how to identify root rot, how to fix it, and how to keep it from happening again.

What is Root Rot?

While it's easy to say root rot is caused by "too much water," it's actually a combination of two things: opportunistic fungi and oxygen deprivation. In a healthy environment, soil is porous, filled with tiny air pockets that allow roots to breathe. When soil becomes waterlogged, these air pockets collapse.

Without oxygen, the root cells begin to die and decay. This decaying organic matter acts as a beacon for fungal pathogens like Fusarium, Pythium, Phytophthora, and Rhizoctonia. These may have been lying dormant in the soil for months. Once the plant’s natural defenses are weakened by the lack of oxygen, however, these fungi take advantage and make the decay problem much worse.

How to Identify Root Rot in Houseplants

Wilting is the first sign of stressed or weakened houseplants. If your plant is slowly wilting and the leaves are turning yellow, crisping around the edges, or dropping, you might be dealing with root rot.

The problem with root rot is that its symptoms look an awful lot like the symptoms of underwatering. (This is because rotten roots are unable to absorb water for the rest of the plant, so while the roots are wet the leaves may be dying of thirst). If you know you've been watering your plant regularly, or if the soil is moist to the touch, it's likely that you're dealing with overwatering.

The only way to confirm root rot is to examine the roots. Gently remove the plant from its container and brush away enough soil to see the root ball. Infected roots will be dark, mushy, and reddish or brown in color. Healthy roots should be firm, pliable, and typically white or tan. Infected roots will appear dark brown or black, feel slimy to the touch, and often give off a distinct, sour odor of decay. Sometimes the outer sheath of the root will slide right off when touched, leaving behind a thin, thread-like core.

How Do Plants Get Root Rot?

Root rot can have two sources. One is prolonged exposure to overwatered conditions that can cause some of the roots to die back due to a lack of oxygen. As they die, they begin to decay or rot away. The rot can then spread to healthier roots and kill them as well, even if the soil conditions are corrected.

The other source can be a fungus in the soil. The fungus may lie dormant in the soil indefinitely and then suddenly flourish when the plant is overwatered once or twice. The root rot fungus attacks the roots and causes them to die and rot away.

Houseplants get root rot when their root systems are left in sodden, saturated soil, whether it’s due to overwatering or soil that isn’t well-draining. The fungi can attack cuttings, seedlings, seeds, and root systems. Infection often occurs in plants that are already stressed. The stressed plant’s root system then begins to collapse. If root rot isn’t treated, the plant can die.

How To Treat Root Rot

If you catch the infection early enough, you can remove the affected parts and nurse your plant back to life. Here's how:

1. Expose the Roots

Remove the plant from the soil and gently feel the roots. Roots affected by root rot will look red, brown or black and will feel slimy or mushy. Affected roots may literally fall off the plant when you touch them. Healthy roots may be black or pale, but they will feel firm and pliable. Rinse the root system under clean running water to clean away any soil that may be contaminated.

2. Prune

Cut away any dead, dying or diseased roots with sterilized shears. It's better to be aggressive here – leaving even a small pocket of rot can allow the fungus to recolonize the healthy tissue. You may have to remove a significant amount of the root system if the plant is badly affected.

3. Balance the Foliage

If you have had to cut away more than 30% of the root system, you'll need to remove some of the foliage, as well. A diminished root system won't be able to support a full canopy of leaves. By decreasing the number of leaves the plant has to keep alive, you'll allow it to focus more of its limited energy on root regeneration.

Re-sterilize your shears with rubbing alcohol and prune back 1/3 to 1/2 of the foliage, making sure to include any leaves that are also showing signs of rot.

4. Repot

Allow the plant’s root system to dry out for 24 hours before planting. Dispose of the soil where the root rot occurred, then wash the pot thoroughly with a bleach solution (or repot the plant in a sterile container). It's very important to sterilize the environment before repotting – otherwise the root rot will just take hold again.

If possible, dip the remaining healthy roots in a fungicide solution to kill off any possible root rot fungus. Repot the plant using new pasteurized potting soil.

How To Prevent Root Rot

There are a couple of things you can do to prevent root rot. Of course, the number one step toward prevention is not to overwater, but making sure the plant has proper drainage, choosing the correct potting medium, and knowing your houseplants’ requirements will help you to prevent this condition.

1. Choose the Right Potting Mix

Preventing root rot requires using the correct potting medium. Potting soil should be pasteurized if possible, aerated, and well-draining and should contain perlite. Never reuse previously used potting mixes, and don’t use garden soil.

2. Provide Good Drainage

Always use a plant container that has sufficient drainage holes. Add peat moss to heavy potting soils to increase draining. Do not allow plants to sit in drainage water.

3. Know Your Plants' Needs

While some houseplants have similar requirements, not all of them do. Research your plants and know what their particular needs are. Some plants need water every week or more often while others only need water every two weeks.

Many plants go dormant when there is less light and sun in the winter. During this period of dormancy, many plants should be watered less.

4. Don't Overwater

Root rot fungi grow and reproduce in wet soil so it’s important to avoid overwatering. Make sure to provide soil that drains well. And don’t forget that drainage holes in pot are crucial for most houseplants.

Most plants won’t need water until the top 2 inches (5 cm) of soil is dry, but again, know your plant’s needs. Also, the amount of water needed is not only dictated by the type of plant but also by the size and material of the pot, the type of growing medium and environmental factors such as temperature, light and humidity. If you have difficulty gauging how much water to give a plant, use a soil moisture meter.

5. Be Careful with Fertilizer

Too much fertilizer can weaken your plant by adding too much salt to the soil. Weakened or stressed plants are more susceptible to diseases.

Final Words Regarding Root Rot

• Only buy your plants from reputable sources that, if possible, are certified root rot free.
• Keep infected plants separate from healthy plants and discard any severely infected plants.
• Sterilize tools and pots between uses. Always use sterile potting soil.
• While it's regrowing roots, do not fertilize the plant, as this may stress it.

Essentials for Fighting Root Rot

• Don't hack away at roots with big pruners. These Fiskars micro-tip shears from Home Depot will let you snip away with precision.
• Always make sure your planters have a drainage hole! This terra cotta set from Amazon is drainage-ready.
• Before repotting, apply a fungicide to your healthy roots to stop the spread of rot. This one from Amazon is great.
• Get a read on moisture with this incredibly popular (and cheap) moisture meter from Amazon.