What Makes an Orchid Plant's Leaves Turn Brown & Dry?

Light

• Novice orchid growers may bring their newly purchased flower home with the only directive for care printed on the label: “Place the plant in a window with bright, indirect light.” Accustomed to ideal greenhouse conditions, an orchid may suffer shock when taken to a new home: strong light from a southern exposure can cause leaves to scorch, whereas weak light from a northern exposure will cause leaves to yellow and die. Either scenario will result in dead, brown leaves.

Watering

• Despite the orchid’s reputation for being tropical, they can suffer just as much from overwatering as from too little water. When allowed to sit in water for days on end, a plant’s roots will quickly rot and die, followed by leaf browning and withering. Too little watering causes desiccation -- though many species of orchid prefer to be watered only once a week or whenever the potting medium has completely dried out.

Pests

• Insect pests such as scale can cause orchid leaves to first turn mottled and yellow, as the piercing action of the insect’s feeding habits damages the leaves. Left untreated, the undersides of the leaves will turn silvery brown, leading to the death of the entire leaf and potentially the entire plant. Mealybugs and aphids can also be problematic, but treatment is simple: gently rinse the plant in warm water, wiping down each leaf and stem with a damp paper towel.

Disease

• Physical deformities in orchids unrelated to pests or culture problems are usually caused by bacteria, fungi or viruses. Fungal and bacterial disease can cause all parts of the plant to rot. Infection usually manifests as watery black spots on leaves, black rot on the roots and bulbs, or downy white growths on the plant and potting medium. Viral diseases are often lethal and extremely difficult to treat though not all infected plants show symptoms. Common infections include mosaic virus, which show up as yellow or black streaks on leaves and eventually causes the entire leaf to brown and die. Another common disease is ringspot virus, which appears as irregular rings and circles on a leaf’s underside and sometimes leads to the plant’s demise.

Nutrition

• While regular feeding of an orchid with liquid fertilizer is helpful for encouraging healthy leaves and bountiful flowering, overfeeding can lead to toxic salt buildups in the potting medium. Excess salts and minerals can cause orchid leaves to brown and sometimes wither. Growers can easily avoid salt buildups by feeding only as often as necessary and thoroughly flushing pots with water once a week as part of the watering and feeding regimen.