Plant Problem Diagnosis Key / Growing conditions
Growing conditions
Edema (oedema)
When roots take up water faster than leaves can lose it, cells burst and form blisters. It follows overwatering in cool weather, high humidity and low light.
Signs
- Small water-soaked bumps under the leaves that turn corky and tan.
- Most often on older leaves of tomato, geranium, ivy and jade.
- No spores or insects in the blisters.
What favors it
Overwatering in cool weather, high humidity, and low light.
Prevention
- Let media dry between waterings; water less in cool weather.
- Increase airflow and lower humidity.
- Space plants for light and air.
Often confused with
Sources
- Edema of Indoor PlantsUniversity of Maryland Extension
- Edema Problem in Greenhouse TomatoesUniversity of Maryland Extension
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
No, only damage or discoloration - Where is the problem?
Leaves - What does the leaf damage look like?
Shape change - What has the leaf done?
Bumps or corky blisters underneath
Not a match? Start the key or describe what you see.
More from university Extension: search Extension pages on edema, or find a plant diagnostic lab through your state's Extension.
Other growing conditions
- Blossom drop
- Blossom-end rot
- Cold and frost injury
- Construction and root damage
- Drought stress (underwatering)
- Fruit cracking
- Girdling roots and a buried root flare
- Heat and light stress
- Herbicide injury
- Leaf scorch and drought stress
- Light bleaching
- Mower, trimmer and animal injury
- Normal fall needle drop
- Not enough light (stretching)
- Overwatering (low root oxygen)
- Road salt injury
- Southwest injury (winter sunscald and frost cracks)
- Sunscald
- Transplant shock
- Winter burn of evergreens