What is edema and what are some ways to deal with it in the garden?

By Heather Rhoades | Last updated: May 5, 2021

Edema, or oedema, is a type of abnormal water retention in plants, often influenced by the plant’s environment.

Favorable conditions actually encourage edema in many cases, since affected plants already have a fair amount of water in their systems and providing them with more can just encourage them to gorge on liquid. Any time a plant takes up water faster than it transpires, edema becomes a risk.

Signs of edema vary between susceptible species, but often include bumps, blisters or water-soaked areas on the undersides of leaves.

These areas may expand and become corky, but in other plants, curling and distortion are common. White, crusty eruptions may form along the leaf veins, or gall-like structures can develop under leaves with yellow corresponding spots on the upper leaf surfaces.

Because it’s not a disease, there are many ways to treat edema, depending on what’s causing the problem. Your job as the gardener is to figure out what’s causing the problem and correct the situation.

If your plant has edema, your first step is adjusting your watering habits. Most plants should never sit in water, so remove those saucers and make sure big pots are draining well.

Roots tend to absorb water faster when the water is warm and the atmosphere is cool, so wait to water until the sun is up in the morning whenever possible.

Indoors, humidity can have a considerable influence on edema, so improving air circulation around plants will help reduce humidity to a safer range.

Increasing light intensity is helpful for many plants with edema, but be sure not to cook them by moving them too quickly into brighter light.

Make these changes gradually, over the course of a week or two, slowly leaving the plant in brighter light for an increasing length of time until it no longer wilts in response to the sun.

Finally, make sure you’re fertilizing your plants properly. Plants with low levels of available potassium and calcium can be more susceptible to edema.

If cultural conditions seem correct for your plants, a soil test may be needed. Adjusting pH levels can make more nutrients available, or you may need to add more of the nutrients that are lacking.

Source: Kristi Waterworth,

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Written by Heather Rhoades

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Heather Rhoades is the founder of Gardening Know How, where she continues to write articles and answer questions relating to gardening.

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