Peace Lily Root Rot signs, Repotting, and Treatment

Peace lily root rot is a common problem in overwatered plants. It will cause various signs like yellowing lower leaves, wilting, mushy base, leaf or flowers falling, and stunted growth.

If you check the roots, they will be black or brown and may have lesions or look mushy and crumbly. Remember, healthy plant roots should be white or tan with any visible white tips.

We have the various causes and signs of root rot in peace lily or Spathiphyllum. We will also give you treatments and tell you how to repot a peace lily with root rot.

What causes peace lily root rot?

Overwatering is the main cause of peace lily root rot since waterlogged soils will cut oxygen from roots. So, they cannot breathe and will begin to die back.

But what causes the decay is Cylindrocladium spathyphylli and Phytophthora parasitica. These are the primary soilborne fungi or pathogens that cause root rot in peace lily. But other fungi like Pythium sp., Rhizoctonia solani, and Sclerotium rolfsii (Southern blight) may also cause it.

Contrary to what many people believe, water alone cannot cause root rot. You can even grow peace lily in water. And so long as you provide nutrients and change the water (provides oxygen), your plant will grow just fine.

But wet or soggy soil will make your peace lily susceptible to root rot and favor the growth of the various fungi that cause the decay. But Spathiphyllum may also get root rot by these means:

• Using a contaminated potting mix or water
• Unsterilized pruning scissors or knifes
• Touching potting mix with dirty hands
• You are placing your plant on the ground or contaminated surfaces. Some species occur naturally in the soil.
• Contaminated pots or planters

We will explain to you shortly how it causes root rot and tell you the pathogens involved. But let us start by telling you factors that may contribute to overwatering. It is not just watering too often.

1. Factors contributing to overwatering

Common factors that contribute to overwatering or soggy soil include:

• Watering too often
• Poorly draining and heavy soils
• Lack of drainage holes
• Low temperature
• High humidity and poor air circulation
• An oversized pot
• Pot type – some, like terracotta pots, help increase moisture loss by allowing water to percolate through them and evaporate on the surface, while others like plastic don’t.

2. How does overwatering affect peace lily?

Overwatering or soggy conditions may make your plants susceptible to root rot-causing pathogens. Also, it favors the growth of soilborne pathogens responsible for the rot.  

a. Affects their usual working and weakens roots

Overwatered or soggy soils will choke oxygen from roots, yet they need oxygen to work correctly, grow and remain healthy, they need oxygen. Why?

Roots use oxygen for aerobic respiration, i.e., to break down nutrients to carbon dioxide, water, and energy, i.e., to produce energy for growth and other functions. Also, without oxygen, they become less permeable, meaning your plant will not be able to absorb nutrients or even water well.

That is not all. Toxins will begin to accumulate because roots can no longer work well. Also, carbon dioxide will accumulate in soggy soils.  

All these three things including make roots vulnerable to opportunistic soilborne pathogens that cause rot.

b. Favor opportunistic pathogens

Moist and wet soil favors the growth of various soilborne pathogens. Thus, they will quickly multiply and attack roots, causing rot.

3. What pathogens cause peace lily root rot?

You know the role of soggy or wet soil. Let us know talk about the various pathogens that cause Spathiphyllum root rot.

a. Cylindrocladium spathyphylli

Cylindrocladium spathyphylli is the most common fungi that cause peace lily root rot, especially during the summer months. This pathogen spreads via water if you keep your plants on a floor and don’t have cache pots.

Symptoms

• Yellow lower leaves
• Slightly wilted or droopy peace lily
• Extensive root damage with the newly infected roots will have reddish-brown lesions
• Plant collapse as the lesions increase within a few weeks to affect the entire root system.
• Crown damage

If the spores spread to leaves, they will cause elliptical penny-sized brown lesions on leaves with a yellow halo. At this stage, the fungus has eaten most of the roots – rotted, trying to pull the play may come off without any roots

Treatment and control

Treatment is by use of a fungicide like Triflumizole (Terraguard®). To control this fungal disease, always clean and sterilize pots and place your plants clean, disinfected, and raised bench or surface.

b. Phytophthora parasitica 

The other common pathogen that causes Phytophthora root rot and leaf spot in peace lily is Phytophthora parasitica. This pathogen spreads via mainly contaminated soil, including when you place your houseplant on infected soil surfaces.

Symptoms

It produces signs similar to those of Cylindrocladium, and they include:

• Leaf chlorosis or yellowing
• Wilting
• Blackening and decay
• Root dieback
• Stems begin to turn black at advanced stages.

Phytophthora parasitica zoospores are very mobile. Thus, they will reach leaves swimming on wet surfaces or if you splash contaminated soil to leaves, including as you water your plant.  

When this happens, you will see black lesions. But unlike of Cylindrocladium will not have a yellow halo.

Treatment and control  

Treatment is by the use of fungicide, with Triflumizole found to be very effective. Also, buy premium potting soils (have a lower risk of being contaminated).

That is not all. It would help if you disinfected pots. Also, avoid placing your plant directly on the soil surface.

 c. Pythium root rot (Pythium sp.)

Poor soil drainage and overwatering will make the soil wet or soggy. This will favor the growth of this soilborne fungus, also known as water mold.

Pythium species naturally occur in the soil. But it is the fungus gnats and shore flies that may carry these pathogens to your potted houseplants. Also, moving infected soil or plant material may spread it.

Symptoms

• Stunted growth
• dead tips at early stages
• water-soaked roots whose cortex will slough off easily, leaving behind the vascular cylinder.
• Stems will rot at the ground level, i.e., crown rot.
• Root discoloration
• Death

Treatment and control  

Check any new plant to ensure the roots are healthy. Then use a well-draining potting mix and don’t use field soil as a growing media. We use Miracle-Gro Indoor Potting Mix or any good aroid mix.

Don’t overwater your peace lily and reduce overfertilization as they will favor the growth of the pathogens that cause the rot.

You can also add well-composted pine bark to your potting mix as it does help control, not just the Pythium but also Phytophthora root rots, notes the University of California.

Last but not least, maintain good hygiene, keep plants off the ground, and use fungicides.

d. Rhizoctonia solani

This fungus pathogen doesn’t present a massive threat to Spathiphyllum. But it may cause Rhizoctonia root rot, and it grows close to the top of your potting mix.

Rhizoctonia root rot spreads by moving plant material, equipment, or soil contaminated with mycelium and sclerotia. Also, it can grow into peat moss, composite, or bark kept on infected surfaces,

That is not all. Soils high in organic matter, warm temperature, high moisture, favors this fungal infection

Symptoms

• It causes rusty-brown, sunken, dry lesions on roots or stems at the soil line, i.e., root and crown rot, that will enlarge, causing sunken cankers.
• Decay of lateral shoots
• Stunted growth
• Leaf yellowing
• Wilting and a shriveled appearance, especially on a hot day
• Aerial web blighting

Treatment or management

Reduce plant stress, feed them properly and use fungicides, especially PCNB. Also, make sure you have a well-draining potting mix and practice proper sanitation.

e. Sclerotium rolfsii (Southern Blight)

This soilborne fungus that causes southern blight spreads by the movement of contaminated soil or plant. Also, infected water or tools can transmit it, and warm moist conditions favor it. Luckily, it is not so common in peace lily. Nonetheless, it can affect them.

Symptoms

• Brown to black rot near or at the soil line that may start as water-soaked lesions
• Girdled stems
• Wilting
• Presence of light brown sclerotia and white, cottony fungal growth on the affected parts
• Sudden plant collapse and death

Treatment or management

Isolate infested plants and practice good sanitation. Inspect any new plant. If you see an infected one, destroy it. To treat this fungus, use a fungicide. Also, soil solarization may help.

Signs of root rot in peace lily

You already have some signs of root rot specific to the soilborne fungus that causes the decay. They are much or less similar. Let us now give you generalized signs and symptoms to expect.

What does peace lily root rot look like?

• Yellowing of leaves or chlorosis:  Since it cannot effectively absorb water and minerals, the lower leaves of your peace lily will turn yellow.
• Wilting:  Your peace lily will wilt or droop, and the wilting will not improve with watering. Also, depending on the pathogen, it may be mild, severe, or sudden.
• Brown tips and edges: Besides wilting, you may notice brown tips or edges, especially if they cannot get water. 
• Stunted grow: These plants will grow slowly (stunted growth) because they cannot get essential nutrients or water from the soil. Also, leaves will be smaller.
• Falling of leaves and flowers: As the rot continues, you may see some leaves and flowers dropping prematurely.
• Moldy and foul-smelling potting mix: The potting mix may look moldy on the top. Also, it may have a foul smell due to the decaying of roots.
• Mushy stem bases: Stems may turn brown or black, look mushy, or have lesions. But this will depend on the exact pathogen responsible.
• Brown or black mushy or necrotic roots: If you examine the roots, they may look soft, mushy black, or brown. Also, they may have lesions.
• Leaf browning and lesions: If it infects the leaves, you may notice brown lesions. Some may have a yellow halo.

Note

If overwatering is the trigger cause, you may see some of the overwatered peace lily signs like soggy and wet soil, brown or black splotches, and yellow leaves that are soft. Peace lily leaf curling is also possible.

How to save peace lily rotting roots

Whether you can save or treat peace lily root rot depends on the extent of damage your plant has. Thus, begin by examining to see the damage. If the whole root ball is mushy, you cannot save your plant. Just discard it.

On the other hand, if you see some white roots, it is possible to save your Spathiphyllum. Here is how to go about it.  

1. Fixing overwatering

Repotting without fixing the overwatering issue will make the same problem recur. So, it will be good to identify the cause and find remedies. Here, you need to:

1. Get a well-draining potting mix. Mixing equal parts of loam soil, peat moss, and perlite or pumice will work.
2. Provide ideal conditions – temperature, light, and humidity
3. Improve air circulation
4. Ensure your pot has drainage holes and is the right size. If possible, buy a terracotta pot.
5. Amend your watering to only when the top one inch of the soil is dry. Don’t follow a watering schedule. Instead, always feel the potting mix with your finger.

2. How to repot a peace lily with root rot

Once you put in place things to prevent overwatering or soggy soil, you need to repot your plant to a new pot or thoroughly disinfect the current one.

What you need  

• Pruning scissors
• New pot
• Bleach solution
• Fungicide

Steps to follow:

a. Disinfect your new pot

Since disinfecting takes a long, we recommend you use a new or different pot. Soak it in a 10% bleach solution, i.e., mix nine parts of water to one part of bleach for several hours.

Next, clean your pot. You can wash plastic pots under running water or soak clay pots in clean water for several hours.

c. Trim brown or black mushy roots

Carefully slide your plant out of the pot, gently break the soil ball and wash it under running water. Running water, get rid of the old potting mix as much as possible.

Then, use a sterilized pruning scissor to cut any mushy, black, or brown roots. Use a solution of 1 part of bleach to 3 parts of water to disinfect your scissors. And when trimming off damaged roots, cut just above a healthy area.

Discard anything you have trimmed and the old potting mix. Never use it again.

c. Reduce foliage

Sterilize your pruning shears again. Then cut back some of the leaves, like ⅓ to ½, depending on how much of the roots you removed. As heartbreaking as it may be, it will help save the energy of your recovering plant.

d. Disinfect roots and repot

Dip the roots in a fungicide solution to prevent reinfection. Then repot your plant to your new potting mix. When repotting, let the soil reach the same level it was before.

Last but not least, keep the soil constantly moist but not soggy. It will help your plant to recover and grow new roots faster.

3. Using hydrogen peroxide on root rot

If the root rot is minor, i.e., has done very little damage, you may not need to repot your plant. Instead, use hydrogen peroxide.

Here, you need to add a tablespoon (15ml) of 3% hydrogen peroxide to a cup of water (240ml). Pour the mixture into a small watering can and evenly water the soil. Ensure it doesn’t touch the leaves.

Frequently asked questions