What Causes Brown Spots on the Leaves of Prayer Plants?

Cultural Factors

• A number of cultural or environmental factors could be the cause of brown spots on the leaves of the prayer plant. Inadequate moisture in the soil or air can be problematic. If the soil does not remain moist, leaves can become curled and spotted. Mist the foliage regularly with distilled water, particularly when there is low humidity in the surrounding environment. Make sure the plant is kept warm throughout winter and avoid exposing the plant to too much sunlight as this can cause bleached or brown spots.

Fluoride or Salt Accumulation

• If the tips or margins of the prayer plant reflect the bulk of the browning or scorch, suspect a buildup of salts as a result of over-fertilization or gradual accumulation over time, exposure to fluoride or some other chemical in the water or soil. Address a salt buildup or over-fertilization by leaching salts out of the root zone. Water the plant slowly and deeply so that water runs out of the bottom of the container, essentially flushing salts out of the soil. Avoid superphosphate fertilizers and irrigating with water that contains fluoride.

Diseases and Pests

• Prayer plants could be affected by a few pests or diseases that impact foliage. Helminthosporium leaf spot, caused by the fungus Drechslera setariae, first appears on leaves as small, water-soaked spots that turn yellow. These spots eventually merge to form large tan areas with a yellow halo. To prevent this fungus, avoid overwatering and apply a protective fungicide like ghlorathonil to healthy foliage. Spider mite feeding can cause small brown spots, or stippling, on the leaves. Avoid letting the leaves become coated with a dust layer by wiping them regularly and misting them with distilled water.

Natural Brown Patches

• One common variety of prayer plant features naturally occuring brown patches on its leaves. Maranta leuconeura "kerchoveana" is sometimes known commonly as rabbit's foot or rabbit's-tracks maranta. The leaves of this variety are variegated and satin-like, generally having two rows that each contain five dark brown patches. These dark brown patches mature to turn a dark green color as the leaves age.