Basil leaves curling can be very alarming and can happen for a couple of reasons such as incorrect lighting, wrong temperature, over watering or pests. If your basil leaves are curling up, we can assure you that your plant is usually not in any real danger, it is just stressed.
In most cases, you can take steps to prevent this from happening again. This guide will help you identify why this is happening and what can be done to prevent it.
Why Are Your Basil Leaves Curling?
The cause could be the lighting, water, or humidity level in your home. It could also be related to how much sun exposure your plant gets. This phenomenon is known as “curling”, and it can happen to any type of basil. 
– Temperature Issues
Basil is native to India and that means it is used to high temperatures. Temperatures outside of its ideal range can cause leaf curling. In more serious cases it could cause plant death due to too high temperatures or, conversely, frost damage.
– Sunlight Deficiency
The first issue is if the plant is being exposed to direct sunlight or not. Basil plants need about six to eight hours of direct sunlight each day – that is a lot of sunlight!
However, if the leaves of these plants do not receive the required amount of light, their foliage begins to transform into a brownish color and shows signs of curling. If this situation continues, small and distorted leaves also follow.
– Irregular Watering
Another cause of curling leaves is if the plant or leaves are not getting watered properly. To this end, both over-watering and under-watering are equal contributors to this problem. While watering your plant, you can check the soil to see if it is still moist. If the soil is too wet, then the plant might develop root rot.
Similarly, under-watering can also prove lethal to the growth of your plant. As the plant stays in the presence of direct sunlight, its store of water runs out quite fast. So, not providing it with enough water also causes the leaves to curl and stimulates wilting.
Basil need to be frequently watered. Watering them only once a week like many other plants simply won’t cut it. Hence, improper watering will lead to malnutrition of the plant. The leaves will begin to turn brown, start curling and eventually fall off.
– Nutrient Deficiency
The leaves of Basil herb plants appear to be thinner and also curl upwards when faced with a lack of nutrients for their steady growth.Leaves turning yellow could be a symptom of a deficiency in the potassium content of the soil.
– Diseases
Some diseases can cause your basil leaves to start curling up. The two of the most common diseases that can create problems with the growth of your basil is powdery mildew and fusarium wilt. Leaf spot or basil plant wilting could be the signs of this.
Powdery mildew
This is a fungal disease that can start growing on the leaves of your basil herb plant and cause them to curl up. Powdery mildew is commonly recognized as the powdery, gray, fuzzy material that develops on the foliage of the Basil.
This disease can easily affect your plant if it is placed in a shady location and provided with insufficient water. If left untreated, it will eventually turn into further severe problems and might even cost your basil plant and any use you might have put it to.
Fusarium wilt
Fusarium wilt is a soil-borne, fungal disease that also causes the leaves of your basil herb plant to curl. The infection caused by the disease interferes with the water that is being conducted up to the leaves through the stem. This in turn causes the foliage of the plant to wilt and turn brown.
– Pest Invasion
If you notice pests on your plant, you need to get rid of them as soon as possible. You can either use a pesticide or use an organic pest control method like neem oil. If you do not get rid of the pests, they can multiply quickly and damage your basil leaves in the long run.
Aphids
These are small sap-sucking insects that attack the leaves of basil herb plants. They cause the leaves to curl up and also stimulate the production of yellow leaves.
Aphids can be serious plant pests as they suck out the plant juices from your leaves that contain important nutrients needed for the healthy growth and development of your plant. Thus, if left unchecked, these pests can cause serious harm to your leaves by causing them to curl up due to malnutrition.
Spider mites
Spider mites are tiny insects that are commonly found in hot, dry conditions. They can cause the leaves of your plants to turn yellow and die. If left unchecked, spider mites can spread quickly and kill your entire plant. Examine your plants carefully, especially the underside of leaves for these tiny pests.
How to Stop Basil Leaves Curling
With proper plant care you can save wilting basil and leaf curling. Here are some tips and tricks to avoid basil leave curling:
– Suitable Temperatures
For basil, night temperatures should remain between 64 and 71 degrees Fahrenheit. Interestingly it will also improve flavor and aroma! If the plant gets damaged due to wrong temperatures you should prune the affected leaves and cover the plant against frost by putting an upturned box on it. 
– Suitable Amount of Sunlight
If the leaves are curling up because of too much sunlight, you can try rotating the plant so that it doesn’t receive direct sunlight or at least place it somewhere where it will receive less sun throughout the day.
If the plant is getting too little sunlight, you can move the plant to an area that receives more sunlight. If you’re growing the plant in a pot, you can move the pot to an area that receives more sunlight when the plant is young.
– Sufficient Amount of Water
Basil plants require regular watering as they like to stay moist. Use a soil moisture meter to see if the soil is moist or dry. You can also use your fingers to feel if the soil is too dry.
The right time to water basil is when the top one or two inches of the soil surface feel dry. Garden-planted basil leaves need to be provided with at least one deep watering each week. While indoor basil plants require watering every one to three days.
It is important to note that these plants require a significant amount of water as they are constantly under direct sunlight throughout the day. You will also need to increase the frequency of the watering in the extremely hot and dry seasons of the year. However, these plants require less water in the cold, winter seasons as water does not dry up as quickly in winters as it does in the summers.
A helpful note is to pot your Basil plant in a container with drainage holes in it so that the excess water can easily get eliminated. This will also help to keep the soil light and dry. Proper watering can also prevent transplant shock.
– Solving Nutrient Issues
The best solution for leaf curling – and to stimulate healthy growth – is to use an all-purpose fertilizer. The recommended ration to be use is 10-10-10.
– Dealing with Powdery Mildew
The key to treating a plant infected with this disease is to place it in a suitable location. Try not to over-water the plant and also allow the excess water to drain out in between watering. In case this disease has already attacked your plants, you will need to cut off the infected foliage to prevent the disease from spreading to other parts of the plant.
There are many chemical treatments to deal with this fungal disease, but one of the most effective treatments include the use of hydrogen peroxide. Just spray a diluted solution of this chemical on the infected plant once a week and get your Basil plant as healthy as ever!
However, many gardeners prefer home remedies instead of using commercially produced fungicides. One common remedy involves the use of baking soda. Many gardeners have found it to be quite effective, too. Just dissolve one teaspoon of baking soda in 1 quart of water and spray your leaves thoroughly with this solution.
– Dealing with Fusarium Wilt
This disease thrives in warm conditions. Therefore, if only one side of your plant is receiving direct sunlight, you ought to rotate your plant regularly.
Unfortunately, there is no treatment or remedy for fusarium wilt. If the symptoms of the disease start to become apparent, such as the wilting of foliage, brown streaks and spots along the stem, and stunted growth, there will be no cure for the infected plant.
Furthermore, it is necessary to uproot and remove infected plants as soon as possible to prevent the disease from becoming airborne and spreading to other plants.
Also make sure to avoid planting any other plant in the previously infected areas, at least for two to three years. Even if the new plant species is not a host for the fungal fusarium wilt disease, it can act as a carrier and infect other plants that are prone to this disease.
– Controlling Aphids
In case your plants have been infected by these sap-sucking insects, there are several solutions for you to use to get rid of these pests.
The first way is to manually remove the aphids using a dry paper towel, and then, crush them. Nevertheless, there are far easier methods to get rid of these pests without having to go through so much trouble.
You can either spray the underside of your leaves with a pressurized garden hose to get rid of the aphids, or even use insecticidal soaps. Moreover, commercially produced pesticides can also be applied.
If the aphids have spread to the entire plant and cannot be reduced, you can cut off the entire Basil plant too. After this, be sure to dispose of the part of the plant cut off, into the garbage to prevent the disease from spreading to other plants.
– Dealing with Spider Mites
In the case of treating a plant with Spider Mites, the fastest and the most natural way is to use a high-pressure hose to drain the spider mites off the basil plant. On the other hand, neem oil or other several insecticides also fare well when it comes to treating a plant infected by spider mites.
You can also mix a dishwashing liquid with some water and voila! You now have an effective home remedy solution that will stick to the invasive spider mites and suffocates them. Just transfer this solution into a spray bottle, shake it up and start covering all the leaves with this solution.
FAQ
Does Basil do well in the heat?
Basil plants thrive in warm temperatures, with 80 to 90 degrees Fahrenheit being the ideal range, along with receiving six to eight hours of healthy sunlight each day. However, in case of dry temperatures, the Basil plant does not survive too well. Growing basil is easy in warm climates.
What nutrient deficiency can cause Basil leaves to curl?
A common nutrient deficiency that can cause Basil leaves to curl is a lack of potassium.
Can Basil leaf curl spread to other plants?
Curling basil leaves are not contagious and won’t spread to other plants.
Conclusion
Here is just a quick recap of everything that you learned today about the causes of basil leaf curling’s and its cures:
- Basil leaves curling happens for several reasons. The first one is if the plant is being exposed to too much direct sunlight.
- Another cause is if the plant is getting too much or too little water.
- If the plant has diseases such as Fusarium wilt, they can also cause the leaves to start curling up.
- Pests like aphids and spider mites are another cause of leaf curling.
- You can prevent this by watering the plant properly, rotating the plant so that it doesn’t get too much sunlight, and getting rid of pests.
In general, this problem can easily be avoided if the necessities of the plants are taken care of.
