What Do Black Tips on My Peace Lily Plant Mean?

Poor Drainage

• If the black areas on peace lily foliage are on the leaf margins as well as the tips and the roots also have black tips, the potting medium or garden soil may be too wet. Peace lilies like to be watered thoroughly -- until water runs out the bottom of the pot. In winter, water the plant less frequently. If the growing medium or garden soil stays wet for several hours after watering, improve drainage. Replace the potting medium with a faster-draining type. In the garden, work some compost into the soil, if practical, but be careful not to injure the plant's roots in the process. If the garden plants aren't too large, consider taking them up and amending the soil, then replanting them atop raised beds.

Excessive Heat or Light

• Spathiphyllums prefer medium to low light. If the peace lily is a potted houseplant, move it to an area that gets less exposure to bright light, and out of direct sunlight. In the garden, especially during the summer, provide some type of shade for the plants such as a latticework wall, and spread 2 to 3 inches of mulch around the root zone to keep the roots cool and moist. Spathiphyllums grow best at temperatures of 90 degrees F or lower.

Phytophthora Disease

• This fungal infection can affect the leaf tips or margins, and if left untreated, may kill the entire leaf. A study at the University of Hawaii found peace lily cultivars Wallissii, Silver Streak, Mini and Tasson susceptible to Phytophthora nicotianae. Keep the foliage dry. Take the peace lily out of its pot and trim away as much of the diseased roots and foliage as possible. Wash all the potting soil off the plant. Dip the roots in a fungicide formulated to treat the disease, then repot the peace lily into a new, sanitary container filled with clean, fresh growing medium.

Cold Injury

• Symptoms of cold injury begin with necrotic, blackened leaf tips. The necrosis then spreads and the peace lily's leaves become dried out and die. Spathiphyllum plants exposed to prolonged periods of temperatures 38 degrees F and lower may suffer cold injury. In severe cases, the entire plant may eventually die. Mini peace lilies are highly sensitive to cold, while the varieties Debbie and Annette are the most resistant to cold injury. Cut the plant back and let the root crown dry out, then set the plant in a well-lit area with indirect sunlight. Resume watering and wait to see if the peace lily produces any new growth. If not, discard the plant and start over.