Oedema, also called edema, is not a virus or fungal infection (thank goodness!), but rather, it is a condition that develops when your plant is taking up more water than necessary for transpiration from the leaves. That’s right, under certain conditions plants are forced to gorge on water, eventually causing the plant cells to burst. The burst plant cells later form whitish to brown cork-like growths, primarily on the undersides of leaves, and as the condition worsens, leaves may eventually turn yellow and fall off.
How to pronounce oedema: uh·dee·muh
What causes oedema?
This natural response to overwatering is influenced by the plant’s environment. Oedema often occurs in conditions where the soil is moist and warm, and the air around the plant is cool and saturated. Oedema becomes more prevalent during late winter and during extended periods of overcast weather. Plants in indoor situations and in greenhouses are often more at risk as these environments create the ideal conditions where plants absorb water faster than it can lose water through the leaves.
Common signs of oedema
Different plants tend to show different symptoms, but generally, signs of oedema include blisters, bumps, or water-soaked patches on the underside of leaves. These areas may progress and form a corky texture, but some plants may curl or distort. In some plants, crusty white bumps form along the veins of leaves or gall-like formations develop on the underside of leaves with yellow corresponding spots on the upper leaf surface.
How do I treat oedema in my plant?
The most important thing you should do is determine what is causing your plant to take up more water than it needs.
- Start by adjusting your watering habits. Your plants should not be sitting in water so ensure that the soil is draining well and that your plants don’t sit in water-filled saucers. Allow plants to dry out between watering.
- Roots tend to absorb water faster when the atmosphere is cool and the water temperature is warm, so wait until the sun is up and the day has warmed up a bit before you water your plants.
- It is important to improve air circulation around plants with oedema to reduce humidity to optimal levels, especially plants grown indoors.
- It is also helpful to increase the light intensity around a plant with oedema. To do this, gradually introduce your plants to brighter light conditions, moving them too quickly may cause the plant to stress and wilt.
- Ensure you are correctly fertilizing the plant and ensure your soil is not lacking in the necessary nutrients and minerals that your plant needs, including calcium and potassium.
- If your plants are in greenhouse conditions, promote conditions that decrease humidity, ensuring proper ventilation and optimal air temperatures whereby plants can transpire.