4 Most Common Causes of Peace Lily Leaves Turning Brown | How to Fix It

Peace lilies, Spathiphyllum wallisi, are a dazzling addition to any household because they are low-maintenance, beautifully flowering tropical perennials that stand at the top of NASA’s clean air list. 

When properly cared for, peace lilies can last for decades, which is why it is so alarming if their leaves begin to turn brown. 

Thankfully, most of the causes of peace lily leaves turning brown are easily fixable and with a little perseverance, can be corrected quickly. So, if this is a problem for you, then read on as this article describes the 4 most common reasons peace lily leaves turn brown and how to fix it!  

Reasons for Peace Lily Leaves Turning Brown

The untimely browning of leaves is a sure indication of a problem with your peace lily and can be caused by issues with soil moisture, nutrient deficiencies, improper climate, or unwanted infestations. These unideal environmental factors lead to necrotic leaves, rotting roots, starvation of plant cells, and a severe decline in the plant’s overall health. 

Chlorosis is the yellowing of leaves and is often the first sign of issues leading to leaf browning, so look out for any color other than your peace lilies’ typical deep green. 

Causes of Brown Leaves and How To Fix

The following four causes are the most common culprits of browning peace lily leaves. 

1. Watering Problems

A sustained lack of water, or repeated overwatering, along with the use of unfiltered tap water are common causes of browning peace lily leaves. 

Overwatering Symptoms

Overwatering makes your peace lily’s leaves appear soggy, wilted, and yellow, which is followed by leaf browning near the bottom of the plant. 

Hold off watering to give the soil a chance to lose excess moisture, additionally, ensure that the catch tray is empty. Top dress with a ½ inch layer of worm castings since leaching of nutrients has likely occurred. 

If, after a week the soil below the level of the top dressing is still soggy I recommend checking the roots for signs of root rot. Remove any diseased roots and replace the soil with fresh, well-draining soil that contains grit, coco coir, and perlite. 

Once corrected, only water when the top 2 inches of soil are dry.

Underwatering Symptoms 

Underwatering causes wilting and leaf chlorosis, followed by severe browning and curling of leaf edges. If a lack of soil moisture persists, then the leaves will crisp and die. 

Water enough to drain through the drainage holes and repeat 2 – 3 times over the next few days. Then, only water when the top 2 inches of the soil is dry. How often this is will depend on your climate. 

During an exceptionally warm spell, you may need to water every few days, especially during the growing season. Remember to water less frequently during times of dormancy.

Using Unfiltered Tap Water

The chemicals, hard minerals, and salts in tap water can cause browning leaves, which follows signs of leaf chlorosis from nutrient deficiencies caused by these impurities deposited in the soil. 

When this occurs, rinse the soil by watering it with the same volume of water as the container the peace lily is in. Allow to drain and repeat several times over the next 3 days. Use only filtered or rain water thereafter.

2. Nutrient Deficiencies

A serious lack of nutrients in the soil is likely to cause browning leaves, most often appearing after signs of leaf chlorosis, curling, and stunted growth. 

Nitrogen (N)

Nitrogen deficiencies will cause the early browning and defoliation of older leaves following leaf chlorosis. 

Phosphorus (P)

Phosphorus deficiencies will cause browning leaf tips, the purplish coloration of older leaves, and stunted growth. 

Potassium (K)

Potassium deficiencies will cause mature leaves to turn yellow and brown, particularly along the leaf tips and margins. 

Calcium (Ca)

Calcium deficiencies will cause brown scorching and uneven chlorosis on new leaf tips.

Feed your peace lily a liquid fertilizer with an NPK ratio of 1:0.5:1, repeat every 2 weeks during the growing season. 

Peace lilies are highly efficient and also sensitive so I find this ratio is ideal because it provides nutrients needed without the risk of a salt build-up in the soil. 

3. Climate Issues

Peace lilies are tropical understory species requiring 7 – 9 hours of bright, filtered sunlight daily. They prefer temperatures between 65 – 75 degrees Fahrenheit, with a relative humidity of 60% or higher. 

Excessive Sunlight Exposure

If left in direct sunlight, peace lilies will likely develop patches of brown, sunburnt leaves on the plant’s top leaves. 

Immediately relocate your peace lily out of the sun, water if the soil feels dry 2 inches below the surface, and trim any brown leaves after a week of recovery.  

Rapid or Frequent Temperature Fluctuations

Temperature fluctuations of more than 10 degrees Fahrenheit outside of 65 – 75 degrees Fahrenheit can cause stress to your peace lily, which leads to wilting, browning, and yellowing of leaves near the source of the temperature fluctuation.

If symptoms occur, immediately relocate your peace lily at least 9 feet from doors, heat sources, or windows in the winter. If needed, water it thoroughly, but wait for at least a week to feed it to give it time to recover.  

Low Relative Humidity 

Extremely low humidity levels will cause browning leaf edges, following leaf yellowing and edge curling. Browning will be most predominant at the tips of your peace lily plants. 

Relocate to an area with at least 50% relative humidity and consider investing in a humidifier if your climate is particularly dry. Once recovered, prune any dead leaves. 

4. Infestations

Bacterial and fungal infections, along with insect invaders love to use peace lily plants as hosts. Keeping your peace lily healthy with monthly wipe-downs and removing all decaying debris will help prevent these infestations.

Fungus Gnats 

Fungus or soil gnats are tiny insects that commonly infest peace lily plants. Over time, soil gnats’ larvae destroy the root system, depleting it of nutrients and opening it up to other infections.  

Leaf browning and yellowing accompanied by a large amount of tiny flying insects near the soil are clear indicators of an infestation. This often leads to nutrient deficiencies, stunted growth, and also leaf drop. 

To rid fungus gnats, add a 1-inch layer of topsoil that contains at least 3 tablespoons of diatomaceous earth. Wait to water for at least 24 hours. Repeat as necessary. 

Mealy Bugs and Aphids

Irregular browning spots can indicate damage from pest predation, usually mealy bugs, and aphids. These damaging pests also deposit bacteria and spores that can lead to other serious infestations. 

To rid your peace lily of aphids and mealybugs, spray with an all-natural essential oil spray containing neem, lemongrass, and lavender oil.

Fungal Infections

Infections such as root and petiole rot of potted peace lily plants are caused by the fungus Cylindrocladium spathiphyllum, which is notoriously very aggressive and hard to treat.   

During the first stage of infection, your peace lily will appear wilted with yellow lower leaves. As the root damage worsens, reddish-brown lesions with yellow halos will appear on the leaves. 

If caught early enough it’s possible that this can be treated successfully by pruning away all traces of the diseased roots. You will need to sanitize your pruning tools after every cut, use a clean top or sanitize the old one and replace the potting soil. 

According to the University of Florida, the best fungicides to treat root rot on peace lilies are as follows:

  • Cleary’s 3336F – Foliar Application (1 oz/5 gal)
  • Fluazinam – Foliar Application (2.4 oz/5 gal)
  • Terraguard 50W – Soil Drench (1.6 oz/5 gal)

If the infection has spread throughout the plant you will need to double bag the plant and soil and throw away to limit the possibility of spreading, then drench the leaves of any other peace lily plants with water and watch for signs of infection. 

Bacterial Infections

Bacterial leaf rot disease caused by the Pectobacterium carotovorum bacteria is an aggressive infection that causes brown necrotic leaves in only 4 to 5 days. 

The first sign of leaf rot in peace lily plants is water-soaked spots near the tips of leaves between 12 – 14 mm in size. Then the infected leaf tissue quickly turns brown and black with yellowish halos. 

There are currently no effective control measures except removal. However, Plant Pathology studies suggest that methyl jasmonate (MeJA) can be used as a foliar application.

This growth regulator should be applied in a concentration of 10 mM and is known to be a long-lasting and very effective treatment of bacterial leaf rot disease in potted tropical plants. 

Citations

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.