All plants can be affected by oedema
Formation of numerous small, water-soaked blisters appear mainly along the veins of the undersides of leaves. These blisters will erupt forming brown, corky growths. In time, the leaves may turn yellow and fall off.
In greenhouses, oedema formation can take place within hours.
This disorder occurs mainly during a sudden change of climate when humidity goes up rapidly and temperatures drop quickly. Such a change within a short period of time will result in plants taking up more water than their leaves can transpire. The outcome will be an excess of watery fluid accumulating in the plant tissues.