Edema
Small watery blisters on the undersides of older leaves that later burst and dry into tan corky scabs. It is not an insect and it is not an infection. The roots took up more water than the leaves could give off, and leaf cells burst from the inside.
Disease checklist
Four things to look for. If most of them match what you are holding, you are in the right place.
What gets rid of it
Gentlest option first. For most backyard cases the first one is enough, so try these in order and stop as soon as it works. If you do spray something, the product label tells you how — please read the notice further down.
1Water less often
Let the top of the mix dry before watering again, especially in cool cloudy weather and through winter.
soil moisture meter houseplantTry this first2Give it more light
Move the plant somewhere brighter so the leaves can transpire off the water the roots are pulling in.
grow light houseplant3Improve drainage
Repot into a fast-draining mix in a pot with a drainage hole, and empty the saucer after watering.
cactus succulent potting mix4Water in the morning
Water early so the plant has warm daylight hours to use it rather than a cold night.
5Move some air
A small fan or wider spacing drops the humidity right around the leaves.
small clip on fan6Leave the marked leaves
Edema is cosmetic and does not otherwise harm the plant. Remove scarred leaves only if you dislike the look.
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Which plants get edema
Every plant we cover that gets edema, grouped by type — tap any one to open its page. A note beside a plant came from that plant’s own entry, because the same disease can be a minor nuisance on one plant and a serious problem on another. Plenty of plants we do not cover get it too.
annuals3
Plant families hit hardest
Related plants often share the same problems, so if one plant in a family has it, check the others. The largest group here is Crassulaceae, with 3 of the 7 affected plants.
- Crassulaceae3 plants
- Violaceae2 plants
When to treat
Cut the watering back the day you see blisters; the marked leaves will not heal but the new ones can come in clean.
Timing only — the label is the law
This page tells you when to watch for edema and when treating is worth considering. It is not a recommendation to apply any particular product. Read and follow the product label before you spray — under federal law the label is the legal instruction, and using a pesticide against it is illegal.
- Check the pre-harvest interval. Every product that’s cleared for an edible crop sets a minimum number of days between spraying and picking. Find it on the label before you spray anything you intend to eat.
- Check the re-entry interval before you or anyone else works in the treated area again, and use the protective equipment the label names.
- Confirm the product is registered for your crop in your state. This page groups many different crops together, and a product legal on one of them is not legal on all of them — state registrations differ too. Your state pesticide agency or local extension office can confirm both.
- Rates and mixing instructions come from the label, never from us. We don’t publish them because they differ by product and formulation.
Other problems on the same plants
If a plant gets edema, these are the problems it most often gets as well, so they are worth checking for while you are out there. They tend to appear together; one does not cause another.