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Edema In Plants – How To Treat (With Pictures)

If you are new to growing plants, be ready to ask the internet all about plant issues and pests. One common problem for home gardeners is edema in plants.

Thankfully, edema is not a major concern, though it does require attention to avoid long-term issues with your plants. If left untreated, plant edema can cause distorted leaves and produce unsightly fruits. In this article, we’ll show you what plant edema looks like and how to remedy the problem.

Pepper plant edema on leaf up close
Edema on pepper plant leaf.

What Is Plant Edema?

Plant edema is a common plant disorder whereby the plant’s tissue cannot properly retain water. It is usually caused by environmental factors. Plant edema is not a bacterial or fungal issue, and therefore does not spread from one plant to another.

You may be more familiar with edema in humans, which can be caused by poison ivy, bug bites, or chronic health conditions. However, the concept of skin edema is similar to that of plant edema. Water is being abnormally retained in an organism’s tissue.

Edema In Plants
Plant edema on pepper plant.

According to a study from Kansas City University, what is technically happening is a buildup of water within cells, ultimately causing them to stretch and collapse.

What Causes Edema in Plants?

The basic cause of plant edema is water being absorbed by the plant faster than it can be used or expelled. As a result, the plant will show signs of collapsed cells.

Environmental factors may include poor air circulation, an abnormal watering schedule, irregular fertilization or crowded plants.

Skip ahead to how to treat plant edema here.

What Does Plant Edema Look Like?

Symptoms of edema in plants may include yellowish bumps or blisters on leaves, white crystallized bumps underneath plant leaves, and eventually brownish dry spots where cells have collapsed.

Many plants will also have curled leaves as a result of edema. Learn more about why your pepper plant leaves may be curling in our article about curling pepper plant leaves here.

Curled Leaf Plant Edema
Severe plant edema on pepper plant.

Some plants may also show these symptoms on the plant’s stems and even on fruits. Badly affected plants may eventually have distorted fruits or stunted growth.

Can Plant Edema Spread?

It is important to know that edema in plants is not a viral disease or a bacteria. It is a cellular disorder caused only by environmental factors. As a result, plant edema does not spread from one plant to another.

However, plant edema can be more problematic for certain varieties. It is known to occur in almost any broad leaf plants. These include peppers, tomatoes, ivy, ferns, cacti, broccoli, and many more.

Edema on small pepper plant
Small pepper plant with edema nearby another plant without edema.

We noticed that some of our pepper varieties had minor edema, while others had none, and a few had bad cases. This just shows how the possibility of edema can be much higher for certain varieties within the same plant species.

How To Treat Edema In Plants

To reiterate, plant edema is thought to be caused by environmental conditions. Beyond changing your plant’s environment, you can try growing a different plant variety that is less susceptible to edema.

Improve Air Circulation

This will mostly apply to indoor growers, as the outdoors offers natural air movement: the wind. However, inside is different.

Just like people need to expel carbon dioxide and take in oxygen, plants need to do the opposite. Allow them to breathe by facing a gently blowing fan towards them or by improving your greenhouse’s air circulation.

We love these affordable clip-on fans from Amazon for easy air circulation.

Having plants stuffed together in tight a grow space or greenhouse can cause stress on the plants. Be sure you have some sort of intake and outflow air system in place to keep the air fresh. Keep a window cracked if possible when the outdoor temperatures are high enough.

Give Plants Room To Breathe

If you grow indoors or in a greenhouse, be sure that you allow enough room between plants. We have limited indoor space for growing our peppers from seed, so things can get a bit cramped.

Transplanting peppers up to larger pots at the right time is key to allowing the plants to grow with enough space. We go from small seed cells to 3.5 inch pots for our pepper plants.

These large, sturdy plant trays allow us to space the plants enough to allow airflow.

Try your best to separate individual plants and get them outdoors whenever possible. If you are growing indoors, be sure to have at least a small fan running to keep the air moving. This will help regulate humidity and will likely help the plants expel water properly. This also helps build stronger plant stems when they are young.

Water Regularly

A study at KCU found that one plant that had its soil kept drier than others actually showed worse edema than those kept constantly wet. Why?

They hypothesized that this could be due to sudden uptake of lots of water after being allowed to dry out completely. After all, edema seems to be caused primarily by an inability for plant cells to expel water quickly enough.

Try to pin down exactly how much water your plants need, and keep to a schedule. Never over-water! Watering regimens will vary from one plant type to another.

We wrote an article specifically about watering peppers here which can help you understand the general principles of plant watering.

Monitor Humidity

Humidity could play a role in plant edema for some varieties. It is unclear, but if the plant you are growing comes from a dry environment, try to simulate that as best you can. On the other side, if you are growing a tropical plant, keeping the air humid (but also fresh) could help abate edema.

A simple humidity/temperature gauge is usually appropriate for any indoor growing. Even if you just have a peace lily or philodendron, knowing the humidity may help indicate when to mist your plants.

Try an affordable temp./humidity gauge to monitor your environment.

Water When Soil Is Warm

Water is absorbed faster when soil is cool, so be sure to water at an appropriate time of the day. Try to water when your plants are warm, ideally early in the day when the sun is not too intense.

Plant Edema Lookalikes

While edema can be treated by changing environmental factors, other issues may look similar to edema. Here are a couple of possible plant edema lookalikes to watch for.


It may seem unlikely to mistake pollen for edema, but some gardeners can be a bit over-worried. Pollen is a natural, dust like substance that falls from your plant’s flowers. It is an essential part of fruit and seed production, and does nothing but help your plant.

Pepper Plant Pollen

Pollen has a dusty appearance and can usually be blown away easily. If your leaves have a whitish dust that easily comes off, it is most likely pollen. Nothing to worry about!

Scale Insects

Scale insects are usually small, white, immobile insects that spread easily from one plant to another. These pests are nearly impossible to completely eliminate, but may be treatable with a neem oil solution or a pesticide.

You can usually tell if you have scale insects if the affected region of your plant is localized. Many types appear clearly insect-like, while plant edema has more of a crystalline appearance. There are many types of scale, so do some research to understand the best way to deal with these pests.

Powdery Mildew

A common fungal disease, powdery mildew affects many different plant varieties. We’ve seen this on our squash plants, but it can affect grapes, maple trees and many more.

Powdery mildew appears as a white, powdery substance similar to powdered sugar. It mostly occurs on the tops of leaves, while edema will usually show symptoms on the leaf bottoms.

This fungal disease spreads easily from one plant to another, so be sure to treat it as soon as you find it. Treatments include a diluted solution of baking soda and dish soap in water, sprayed on the affected areas.

Read Next:

I hope this article helped you get a better understanding of edema in plants. Thankfully, plant edema does not spread and can usually be remedied by a few environmental changes. Good luck, and happy gardening!

Calvin Thumbnail


One of the original Pepper Geeks! When Calvin isn’t gardening or learning more about peppers and botany, he might be traveling new places or playing some music.


Sunday 20th of March 2022

If I can be of any help, I have a grow tent with a 3 level shelf wjere I grow tomatoes peppers and mesclun. I have learned that when your soil is at 25 celcius and the air too during the day, the plants are doing fine with oedema. Its when the lights turn off that the bad thing happen! Your soil stay hot longer than your ambient air and without the lights on to heat the air, it start getting colder much faster than the soil is. So the plant close its stomata because of the cold temperature but the roots are in a hot soil so they keep pumping water up in the leaves which make the leaves cells rupture. My grow tent is in my basement at 18 celcius. In the tent its 25 celcius, so when the lights turns off, my blower must do too or I will make the temperature drop too drastically.

I also read about over feltilizing, when you have a high concentration of nutrient in the leaves, it prevent a good transpiration due to osmosis effect. Water always tend to go to the most concentrated environment, in this case the leaves.

The best tips I can give is to find ways to not over water plants, over fertilize them, to get a good ventilation system and to keep the growing area protected against quick temperature drop when the lights turn off


Monday 17th of May 2021

Great info. I have a few plants that have edema, most likely caused by crowding: air circulation. I have 75 pepper plants and 80 tomato plants hardening off as we speak(7a). I’ve moved them all out to a detached garage and have them on a 4x8 piece of plywood attached to a couple of dollies, makes it easy to pull in and out of the sun.

Question I have is I have everything from sweet snacking peppers to cayennes, to super hots. I use drip irritation, any suggestions on watering based on species and pot size?


Tuesday 18th of May 2021

Sounds great, hopefully we can get to that level with a dolly for hardening off. No real suggestions for drip irrigation based on plant species..but I'd say just check the soil for moisture level before watering each time to avoid over doing it. As for pots, the larger the pot the less frequent watering should be necessary. However, on hot days, even a large pot can run out of water fast!


Monday 19th of April 2021

What a great article. A couple of my plants have edema. They’ve grown so big. I check on them every day. Multiple times a day. I swear they’re like children. I am constantly out there peeking at them. Looking if they grew anymore from last time I checked. Ridiculous. This is an obsession. I’ve kept mine on heat mats since I started them from germination, and under grow lights. I live in zone 6B Connecticut. It’s too cold to plant them outside. My question is how high should the T5 grow lights be kept from the plants. And should I keep the heat mats on. We have a make shift grow tent to keep them warm. And open up one of the sides so the fan can blow on it. However tho I have to water them every other day. They dry out so fast and then the leaves start to curl. I’m worried that they’re drying out too much. Any tips??


Tuesday 20th of April 2021

Hi Vita,

I feel the same way about our peppers - very attentive to them! As for the lights, T5 bulbs should be kept pretty close to the foliage, usually around 3-4 inches. The reason is that fluorescent bulbs scatter a lot of light quickly as you move away from the light source. If you move them closer to the plants, check back in after a few hours to make sure the leaves aren't showing signs of stress.

As for the heat mat - we shut ours off right after the seeds germinate. Our indoor temperatures are warm enough for the plants once they sprout (between 65-75°F). The dryness will just come down to your local climate - heat tends to dry them out, so I'd say shut off the heat mat!

As the plants grow, the relative humidity will also rise in the grow tent due to the plants transpiring moisture through their leaves.

Happy growing! -Calvin


Friday 19th of March 2021

Thank you sooooo much for this article!

I started some peppers from seed, too early (had some bad advice about how early to start from elsewhere). I have great (2300 lumens 6000k) and also cheap (not branded as grow lights) LED lights that the peppers just loved and I was so happy.

I potted them up into 6" pots, and eventually they got too tall for the shelves with my lights, and it's still not warm enough at night to plant them out. I had to move the plants around a lot to keep them from touching the LEDs, the leaves were curling. And meanwhile, the fungus gnats are horrible (fighting them now with BT mosquito bits and yellow glue traps).

So, okay, I'm doing all I can to shepherd these beautiful plants, that are starting to have actual peppers on them, through the next few weeks until I can plant them out. I'm running out of space indoors. And then I see these white crystals on the underside of leaves of a few plants that were already curling. What new hell is this! I was so excited about how well everything was doing, a while ago that is, and I wanted to give away plants to friends.

Anyway, your article gives me new hope. Live and learn, and I'm learning a lot from this experience. And glad that it doesn't look like a total loss!

Tony Rhodes

Wednesday 11th of November 2020

You might add improving light to help resolve edema. I had an issue and, thinking for a few days that I did not have enough light, purchased a new full spectrum LED light for my indoor peppers. Within two days the leave curl was gone and my bonchi plants started shooting up again.


Tuesday 23rd of March 2021

Hi Tony - thanks for the tip!

I've started moving the plants outside for a little bit each day, hardening them off, since the weather is really nice during the daytime. Gradually increasing the time outside and bringing them back in - no overnights outdoors yet! So hopefully that will help. And I just up-potted a bunch of plants into the next size pot. Fingers crossed!

I was under the impression that a 6000k light was full spectrum, but maybe I should up it to 6500k. Anyway, thanks for your help!