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Basil Leaves Are Turning Yellow And Curling

Publish Data: July 5, 2021

by Mumtahina Piya

We all know that basil is a hardy plant that can easily survive a little bit of the harshness of nature. But that does not mean you will not face any problems while growing basil in your herb garden. There are many problems that you may face during basil cultivation.

Out of those problems, we often face the problem of yellow and curly leaves. Sometimes you may notice that the leaves are turning yellow or curling up or down. So, to solve this problem, you have to know why they are turning yellow and curling.

Basil leaves can curl and turn yellow due to overwatering, too much or too little sun, disease, or pests. So these are the main reasons for all those curly and yellow leaves on your basil plant.

So, I am here to give you the details of the cause and solution to the problem. Let’s dig deeper!

Basil leaves turning brown
Gardening at 58 North / YouTube

Why basil leaves are turning yellow and curly

As you already know that basil leaves can turn yellow due to overwatering, fungal diseases, pests, malnutrition, or not getting the right amount of sun. Nobody wants some yellow leaves on the plant in the place of some fresh green basil leaves.

Here I have mentioned five causes of it. So, let’s know about those!

1. Frequently deep watering or overwatering!

The most common cause for turning leaves yellow is too much watering. Basil likes moist soil but can’t tolerate soggy soil. So, if you notice the yellow and curly leaves on the plant, you can be sure that the watering is way too much.

Maybe you are using poor drainage clay soil for the plant. Or else, the drainage holes are not enough to drain the excess water. As a result, the excess water will turn the soil soggy.

Besides that, the soil surface is not dehydrated, but you are adding water to it. So, then the over-watering will cause the problem, and soon you will have yellowish and curly leaves on the plant for sure.

2. Providing the sunlight to basil in a wrong manner

Basil is a sun-loving plant. Basil needs direct sunlight for 6 hours per day. But when you place it in a shady place, it can’t get enough sunlight. So when it doesn’t get that amount properly, it tends to curl and turn into brown leaves.

3. Disease attacks can be severe!

Another cause for curling and yellow leaves is a disease. The root rot and some fungal attacks cause the basil leaves to turn yellow and curly. Over-watering can consider as the main culprit for fungal attacks as soggy soil can attract fungus or bacteria to the plant. Let’s discuss those diseases.

Rotten Root Disease

Root rot is mainly a fungal attack on the roots due to over-watering. The fungi create mold on the downside of the plant, and that causes the roots to rot. As a result, the leaves will start to turn yellow and curly, and eventually, the plant dies due to root rot.

Downy Mildew Disease

You can easily trace the presence of downy mildew disease by tracing the drooping leaves and yellow spots on the leaves. A humid environment encourages this disease to grow. When you kept the plant in a moist environment with poor air circulation, this disease can effortlessly attack your plant. So, it is better to locate the plant in a place where it can get fresh air.

Powdery Mildew Disease

It is another fungal disease that can be the cause of curly leaves. You can notice the curl leaves along with powdery stuff on the leave’s surface. Too much watering and shady place encourage this disease to grow on the plants.

Fusarium Wilt Disease

This deadly fungal disease will turn the leaves curly and brown. In this disease, there grows fungus on the plant that ultimately kills the plant.

4. Either too much or no fertilizer for fighting nutrient deficiency

Indeed, basil doesn’t need heavy fertilization. But a light fertilizer can help the basil to get the nutrition for its growth. Due to nutrient lacking, basil leaves can turn yellow and curly. Also, due to nitrogen deficiency, the basil leaves can turn yellow.

However, using too much fertilizer can cause the leaves to burn, and the leaves can be curly due to the fertilizer burn.

5. Pests are unwanted guests sucking the leaf’s fluid

If you notice a pest on an individual leaf, be sure the entire plant is under pest attack. When the foliage is turning yellow, check the underside of the foliage. If you notice some small substance on the back, the pests are here!


These sap-sucker insects attack the underside of leaves. Because of this insect, the leaves will curl and turn yellow. This pest can suck all the fluid and nutrients from the leaves that cause the leaves to become curly and turn yellow. Even the plant can die if you don’t take care of the affected plant.

Spider Mites

It is also like aphids, sucking the leaf’s fluid. Initially, you can notice yellow or brown spots, and gradually the leaves start to curl after the attack. You may not see this pest on the leaves. So, shake the plant softly, and some white stuff falls from the plant. Then, you can be sure of its existence.

Five ways to prevent yellow and curly leaves on basil

So till now, we have discussed the causes of the curly and yellowish leaves. Now it’s time to discuss the prevention of this disease so that the basil can have healthy growth. Let’s jump to the solutions.

1. Stop doing overwatering!

Many people misunderstand the moist with overwatering. Moistening the soil doesn’t mean overwatering. Basil doesn’t need lots of water! Only one inch of water per week is okay for it. Water basil once after every two or three days based on the soil moisture. Other times, you can just moist the soil using a spray bottle, but don’t let the water touch the leaves.

2. Place the basil in a sunny spot!

As basil requires 6 hours of sunlight per day, it is better to put it in a sunny spot. But make sure to protect it from the harsh light of afternoon shade. Also, be aware of the temperature as it shouldn’t be 90 degrees or more. Also, it will better to avoid sunburn.

3. Keep the fertilizer under check!

Basil also needs fertilizer like other plants. You can use some liquid fertilizer once every couple of weeks in a small amount. Or you can use a slow-release fertilizer in the soil or potting mix and re-fertilize it again after six months.

4. Fighting against the pests

For fighting against the pest, you can use chemical pest control spray or insect soap. Follow the package instructions for applying them.

Besides that, you can use a predator, like a ladybug, for taking down the aphids. The aphids are the tasty snacks for ladybugs, you know! Or else use neem oil to keep the pest away.

Sometimes, ants can invite those pests to your basil. So, it’s better to keep the ants away. For that, you can either use ant-killing medicine or cinnamon powder in the soil.

Moreover, you can use some companion plants like garlic or zinnias. They will work well as a repellent for keeping the pests away.

5. Fighting against the disease

Now to talk about the disease. The only remedy to keep sickness away is to keep the basil in a sunny spot and away from soggy soil. Most of the fungus attracts to the plant because of the wet soil surface or wet leaves. So if you give them a warm environment and the right amount of water, neither the plant nor the soil will remain damp.

However, if the disease attacks a single plant, it is better to remove the sick plant as soon as you notice it. The fungus can be contagious to affect the other plants in the garden.

Few last words for you

Don’t be upset if your basil leaves have turned yellow or curly. It is common to face some problems during the gardening journey. But you see, I have mentioned all the possible causes and the solutions for solving those problems. I hope these will help you with your basil problems. Have a good gardening journey, Happy Gardening!