5 Causes of Pepper Leaves Curling in Greenhouse (with Solutions)
I have been growing bell peppers in polycarbonate greenhouses, often with leaf-curling challenges.
Have you ever wondered why that happens and what steps to take? Read on, and let’s delve into this together.

1- Harsh Growing Conditions
When I notice the leaves of my greenhouse-grown peppers curling, I make it a point to identify the initial symptoms. This can be related to uneven seedling development or improper care.
Leaf deformation can vary: sometimes, they curl along the main vein, and often, alongside the curling, there’s a change in color or shape. Leaves may bend inward, outward, downward, or upward.
The key reason behind leaf curling in vegetable crops is the plant’s response to uncomfortable growth conditions. Greenhouse conditions are different from outdoor ones.
Enclosed spaces often lack adequate air and are frequently dry and stuffy. Due to the dry air, the pepper leaves curl inward, like a “boat” or a “spiral.”
Moisture rapidly evaporates from the leaf surface, causing the leaves to lose their elasticity and density – an especially devastating blow for newly transplanted seedlings.
You can save the plants by lowering the temperature. For prevention, it’s essential to ensure a comfortable humidity level in the greenhouse. To achieve this, I place containers with water at various points.
2- High Temperature
Greenhouse plants suffer from hot air inside the space. Spraying and watering often don’t solve the problem. The leading cause is intense sunlight.
The plant experiences stress, signaling it through wilting and curling of leaves. The temperature drops a bit in the evening, and the leaves uncurl slightly with proper watering.
In such conditions, the root system can’t independently compensate for the lack of evaporated moisture.
The only thing I can do is monitor soil hydration and ventilate the greenhouse more frequently.
Leaf curling is typical when there’s a water deficit. They wilt, wither, and dry out at the edges. Bell pepper, a moisture-loving crop, can react even to the slightest changes in conditions.
The solution to the problem is normalizing the watering schedule. It’s important to ensure the soil inside the space stays moist. If it’s too hot in the greenhouse, water daily.
In small spaces, you can plant on a hydrogel. This polymer has the ability to store water and release it as the soil dries. It is added to the soil at planting time, ensuring it doesn’t contact the root.
3- Development of Rot
If the pepper leaves are curling and darkening, it’s too damp in the greenhouse, creating an environment for infection.
The plant suffers from an excess of water too. The darkening indicates the development of fungus and root rot.
Leaf curling is the first sign of trouble. If it spreads, neighboring bushes could be affected.
In this case, urgent measures are needed. The disease targets weakened seedlings lacking calcium.
To prevent this, I fertilize and treat with fungicides timely.
4- Wrong Care
Without proper care, plants often fall sick and die. After transplanting them into a greenhouse, they need constant attention without forgetting about staking and shaping the bushes.
Often, leaves curl inward at the top, like a “boat,” due to uneven growth of the leaf’s central vein and blade. With proper care, the leaves can regain their normal shape.
Sometimes, I forget to ventilate the greenhouse often enough, completely forget about watering the plants, and neglect to fertilize the soil.
As a result, it gets depleted, and the plants lack potassium, magnesium, and phosphorus.
I solve this problem by adding a complex organic fertilizer. This could be wood ash, which I sprinkle under each bush (about one tablespoon), then perform loosening and watering.
I also use wood ash for liquid feeding. In this case, I mix it with water (1 cup per 2.6 gallons), let it sit for a day, and pour around 17 ounces under each bush.
Providing the pepper plants with an optimal microclimate and necessary conditions is crucial. Leaf blades can deform due to soil causing seedling diseases.
The soil in the greenhouse shouldn’t be overly acidic. That hampers the roots from absorbing nutrients.
It’s important to keep an eye on the balance of trace elements. The plants ‘ leaves curl when there’s an excess or a shortage.
- The pepper lacks potassium when the leaves curl upwards, and the edges dry out and crumble.
- With a phosphorus deficiency, the color turns purple, and the shape resembles a “boat” sticking to the stem.
- With excess potassium and a lack of magnesium, the areas between the veins in the leaves turn yellow and darken.
- A calcium deficiency is expressed in the rising of the edges and bumpiness of the blades, with the gradual appearance of yellow-brown spots.
The lighting should be sufficient. Also, it’s a mistake to skip soil treatment. This leads to a build-up of pest larvae in the soil, which later infest the plants and cause significant harm.
Moreover, considering bell peppers are a bit finicky to grow, you must watch out for temperature fluctuations. The plant’s leaves curl and fall off with a sudden temperature change.
For root feeding, you can use nitrate and potash fertilizer. Dissolve the fertilizers in water (2 tablespoons per 2.6 gallons or 10 liters) and add to moist soil.
5- Diseases and Pests

The above-ground parts of the pepper plant often suffer from harmful insect attacks, signaled by the curling and wilting of leaves.
You can usually identify the cause of the damage visually. Signs include spider webs, a whitish coating, and yellowing of the leaf blades.
All these signs suggest that the plant has fallen victim to aphids, thrips, spider mites, or whiteflies. To get rid of these pests, you need to use specialized strategies.
These can be chemical substances, biological products, or home remedies. Effective treatments include using Insecticidal Soap for Plants and Pure Neem Oil.
If you’re hesitant about using chemical sprays or substances, you might want to consider biological control methods.
These involve using natural predators, like ladybugs, to control aphids and spider mites.
These little critters are the natural enemies of these pests and are incredibly effective in keeping your pepper plants pest-free.
You can find these helpful bugs in garden stores or even on Amazon.
Removing the bush and treating the soil makes sense if the damage is extensive.
Manually removing aphids or other pests is pointless. This measure is ineffective and doesn’t yield results.
To boost the plants’ immunity, some people use stimulants. Some use a soapy solution, onion peels, or wormwood.
Often, the plant falls prey to apical rot and verticillium wilt. It happens due to intense heat; the blade’s edge becomes wavy.
Then it bends upwards and turns yellow. In this case, you have to get rid of the affected bushes.
For the treatment of fungal diseases. Here are the fungicides I recommend:
Name of The Fungicide | Amount | Amount of Water |
Bonide 811 Copper 4E Fungicide | 1-4 tablespoons (.05-2.0 fl oz) | 1 gallon of water |
Garden Safe Brand Fungicide3 | 2 tablespoons (1 fl oz) | 1 gallon of water |
Southern Ag – Liquid Copper Fungicide | 3-4 tablespoons | 1 gallon of water |
As home remedies, you can use onion, garlic, or whey. They’re effective in the early stages of the disease.