Edema (oedema) is a physiological condition in which rough, corky swellings form on the petioles and on leaves, most noticeably on the undersurface. These protrusions initially are darker green than surrounding areas, later becoming brown. Excessive soil moisture and poor lighting coupled with low temperatures and high humidity predispose plants to edema. It occurs most often during the winter on succulent plants grown indoors. Ivy geranium, peperomia, viola, eranthemum, and shefflera are often affected. Ivy geraniums are more susceptible to edema than zonal geraniums. If injury continues, the leaves turn yellow, droop, and fall from the plant. Leaves showing symptoms of edema will not recover, but you can halt the decline of a plant by improving light levels and watering less often. Repotting to improve soil drainage may also help.

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