Why Is My Orchid Turning Brown?

Sunburn

• Most orchids require bright but indirect sunlight, as this mimics their natural habitat beneath canopies of jungle trees. Too much light burns orchid foliage, leaving dark brown sunburn spots that are dry and sometimes crack. You can predict sunburn when you notice leaves turning yellow-green and softening, indicating they are receiving as much light as they can take.

Diseases

• When they come down with a disease, orchids may not showcase many symptoms. When they do, one of the most common is dark spots on the leaves, according to plant pathologist Paula Flynn on the Iowa State University website. These ringspots--typically brown, black or yellow in color--indicate a viral disease. The virus also presents on the flowers, which have brown streaks or light-colored breaks in their natural color.

Rotting

• Fungal and bacterial rot browns or blackens leaves. Black rot begins on the leaves as purple-brown spots that gradually blacken, while root rot causes brown areas stretching from the roots to the leaves, which twist and wilt. These problems occur when gardeners give orchids too much of what they require: humidity. Wet foliage that never has time to dry leads to rot.

Expert Solutions

• To prevent sunburn, Clemson University horticulturalists recommend hanging a sheer curtain in the window to shade orchids when midday sun hits. An east-facing window is the safest spot for Phalaenopsis orchids to receive bright light without taking a beating from the sun. Cattleya may prefer a brighter west-facing window. For fungal rots, cut off the infected spots and treat with a fungicide. As an alternative to fungicide, the American Orchid Society suggests coating the cuts with cinnamon. The only incurable problems are viral diseases. Both Flynn and the University of Illinois Extension recommend getting rid of infected orchids immediately--preferably by burying or burning--to prevent the disease from spreading to other plants.