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.
Pepper Geek participates in various affiliate programs, meaning links contained in this article may provide us a commission should you make a purchase on the linked website.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 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.
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.
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!