What Causes Basil Leaves To Turn Black?

The basil plant leaves turn black due to the presence of anthocyanins. Anthocyanins are a pigment responsible for the red, blue, and purple colors found in many fruits and vegetables.

They are also responsible for the black coloration of some leaves. When anthocyanins are present in high levels, they can cause leaf tissues to die and blacken.

Frost, bacterial or fungal infections, pest infestations, or a lack of nutrients in the soil can all cause black or brown spots on basil leaves.

How to treat and prevent it from happening again, dig this guide.

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Four common causes for basil leaves to turn black

Spots on leaves are a symptom of various underlying problems, so there is no single cause for them.

The following are the four most likely causes of blackened basil leaves: The following are the four most likely causes of blackened basil leaves:

Exposure to Frost

Basil is a tropical and subtropical herb that will die if exposed to freezing temperatures or frost.

This happens if you plant basil too early in the season or an overnight cold snap, and the leaves begin to turn black and die due to this shock.

Fungal and Bacterial Infections

Insects or water splashing on the leaves of your basil plant can spread disease pathogens that cause black or brown patches on the leaves.

Black or brown spotting on the leaves of your basil plant can be caused by fungal infections such as Colletotrichum, Septoria, and Cercospora Leaf Spot.

Wet, brown patches appear on the leaves and stems of plants infected with Pseudomonas Cichorii, a bacterial disease. However, downy mildew is not a fungus but a parasitic organism.


Aphids, thrips, and spider mites are just a few of the pests that like to feast on basil. It is possible to see tiny black spots on the leaves, or leaves punctured and fed on will begin to turn black and fall off if an infestation is not treated in time.

They are more likely to attack weak or vulnerable plants or to spread from other plants of the same or a different species that are already being attacked by the pests they feed on.

Nutrient Deficiencies

Lack of nutrients is more likely to result in yellowing or curled leaves than black spots on your basil leaves.

Yellowing and dying leaves can eventually turn brown or black due to nitrogen deficiency or excess application.

This could be the problem if you’ve ruled out all other possibilities.

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How To Identify Black Spots On Basil?, 4 Common Causes

The presence of black spots on basil leaves is usually a symptom of a fungal disease. The most common fungus that causes this problem is Alternaria alternata. This fungus can cause dark brown or black leaves in color. A yellow halo may also surround the spots. 

what causes basil leaves to turn black
What Causes Basil Leaves To Turn Black? 3

If your basil leaves are covered in black spots, you can try various methods to discover what’s going on.

1: After A Cold Snap

Find out if there have been any overnight temperature drops by looking back at the forecast from the previous week and checking it out.

Black spots or tips on your basil leaves after a night of temperatures below 50°F (10°C) are almost certainly due to exposure to cold or freezing temperatures. Leaf spots can be small or large, depending on the severity of the condition.

2: Look At The Spots And Rings Color

Although it can be difficult to distinguish between fungal and bacterial infections, they usually have different colors, textures, or rings surrounding them.

As the disease spreads, wet, dark spots will appear on the leaves of Pseudomonas Cichorii, a bacterial infection.

Colletotrichum is a fungal disease that causes leaf spots to turn black and fall off, leaving an inconspicuous hole in the leaf’s surface.

Symptoms of Cercospora Leaf Spot include large black spots surrounded by a yellow ring and eventually develop a white core.

After that part of the leaf dies and dries out, they can also fall out. Septoria fungi spots will appear gray/brown rather than black, and a dark brown halo will surround them.

3: Black Spots On The Leaves

A black or brown mold-like substance is likely to be found on the underside of your basil leaves if you see it.

At the beginning of the infection, it can only be found under the leaves and is the best way to identify it. Once it has spread, the tops of lower leaves will also be affected.

4: Leaf Webbing, Stickiness, Or Eggs

Aside from the black or brown spots on the leaves of your basil plant, pests like aphids, thrips, and spider mites usually leave other signs of their presence.

Insect feces can be found in the black spots, but it’s also possible that the plant tissue has been eaten away.

Tiny bumps on the leaf’s surface area where thrips lay their eggs, so look for them.

There are larger aphids, which can be seen on the leaves if you look very closely, but they also excrete sticky, clear fluid excrement that resembles honey in appearance.

Spider mites, which can be as small as a millimeter in length, are known for the fine webbing they leave behind between the leaves and at the stem’s base.

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How To Treat Black Spotted Leaves?, 3 Simple Methods

At this point, you are likely to have figured out what’s behind your black spots (or at least narrowed down your list of possible culprits).

If your basil plant has become brown and shriveled, we’ll show you how to resuscitate it so it can produce more sweet basil throughout the growing season.

1. Cold Exposure

Unfortunately, there isn’t much you can do to ‘cure’ your basil plant if it turns black because of the cold. Pruning away all of the affected leaves is the only option you have.

Because of the damage caused by cold and frost, basil’s black spots indicate necrosis, which is irreversible and will continue to spread if left on the plant.

Using a sharp snip close to the stem, remove any dead or dying leaves from the plant.

Cover the basil plant with bell jars and tents to prevent future colds. We are using hoop tents to protect basil from short-term cold weather. Keep the planting soil at the same temperature for the entire time. For this reason, wet soil is preferable to dry soil.

Consider bringing your outdoor plants inside during a sudden cold spell, or at least moving them to a protected location like a porch or close to a building until the weather warms up again. If you want to avoid temperature fluctuations, you can always grow your basil indoors all year round.

Fresh leaves can be harvested and preserved by drying or freezing them in other recipes.

2. Fungal And Bacterial Infections

Organic bicarbonate-based fungicides can be used to treat many bacterial and fungal infections in basil if they aren’t too advanced.

Before applying the solution, remove any leaves that are infected. A liter of water, a half teaspoon of baking soda, and a few drops of natural dish soap are all you need to make this protective spray at home. Powdery downy mildew can also be treated with this if you catch it early enough.

All infected plants must be destroyed to prevent the disease from spreading to other crops within a reasonable distance.

It is recommended that diseased plants be burned or thrown away with care after being removed from the landscape. These specimens should not be composted to prevent the decaying plant from being eaten by fungi and bacteria. Then it may spread throughout your entire yard.

3. Pests

Synthetic pesticides can harm beneficial insects and your soil, so this method is preferred. On the other hand, Using neem oil, basil leaf miners can be eradicated. You can buy this natural pesticide, made from the neem tree, online or in most garden centers.

Using the same dish soap and baking soda combination spray for fungal infections is possible to treat and eliminate spider mites.

Pruning away severely damaged leaves will help the plant get a fresh start. To ensure that any eggs laid by pests in the old soil do not survive underground, all potted basil plants should be repotted with fresh soil and a mixture of organic fertilizer.

4. Nutrient Deficiencies

If you suspect that your basil is suffering from a nutrient deficiency, the best way to support your plant’s recovery is to adjust your fertilizing and watering schedules.

If you haven’t fed your basil plant in a while, consider applying a layer of compost or organic nitrogen fertilizer.

A second option is to stop fertilizing for a month and observe whether or not your basil recovers from its over-fertilization.

If you notice spotted leaves on a healthy plant, you should remove the afflicted ones.

Preventing Your Basil From Developing Black Spots

A garden plagued by disease or pests is a much more difficult task than preventing them from ever getting there, to begin with.

To keep your basil plants healthy and resilient, you must first create an ideal growing environment for them.

Heat, sunlight, good air circulation, sufficient nutrition, and semi-dry conditions are essential for the success of basil plants.

Preventing black spotting is as simple as following these guidelines:

Keep your plants at least a foot apart from each other and away from humid areas to ensure adequate air circulation. Despite the additional warmth provided by greenhouses, basil may be more susceptible to fungal diseases because of the high humidity.

When plants are crowded together in the garden, the lower leaves of the plants will be unable to dry out in the sun, resulting in damp conditions that both bacterial and fungal diseases can use to grow.

As wet leaves are a primary pathway for bacterial leaf infections, water your basil plants first thing in the morning and directly at the base of the plant.

During the hottest months of the year, basil should be watered several times a week. They can be watered in the morning so that any leaf droplets can dry before the cool evening temperatures arrive.

Basil thrives in soil that is well-balanced in nitrogen, potassium, and phosphorus and has good drainage. Growing basil in a pot or container and bringing it inside when temperatures drop is an excellent way to maintain soil conditions while also protecting it from the cold.

When temperatures are still cold, transplanting seedlings into the ground too early in the spring is a sure way to kill off your plants.

Once a week, inspect your plant thoroughly for any signs of pests so that you can treat it with neem oil before any severe damage is done. If you take these precautions, you will be less likely to encounter a pest infestation because pests prefer weak or sickly plants.

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Can You Eat Basil With Black Spots?

The leaves of your basil plant are safe to eat even if they have black spots. On the other hand, the leaf may have a distinctive flavor all its own. Basil leaves that have been damaged are likely to taste bitter and, in extreme cases, may even be a bit slimy. When possible, use fresh green leaves instead of dried-out ones!

Will The Leaf Spot Go Away On Their Own?

Leaf spots will not go away on their own if a fungus or bacteria causes them. If you have any other basil plants or leaves nearby, they will also be infected. Remove the infected leaves and clean your gardening tools with soapy water as soon as possible.

Sulfur or copper-based fungicides applied weekly or biweekly can be used to treat the plant going forward, depending on the severity of the condition.

Should You Change The Soil Of Black Spot Basil?

If insects cause the problem, I’ll usually remove the soil and replace it. Additionally, I prefer to use a high-quality potting mix.

Can I Bring My Basil Plant Back To Life?

You can give your basil plant a second chance by doing a few simple things. Give your basil a good drink of water if it’s starting to wilt. Allow the soil to absorb the water for a few days before adding more. Avoid heat stress by moving your basil into the shade and giving it a few hours of vigor. To prevent mildew, remove any basil leaves that cannot be saved.

What Is The Best Way To Store Basil?

Keeping basil in the refrigerator for up to three days is as simple as harvesting, washing, letting it air dry, and then wrapping it in a paper towel. Basil keeps best at room temperature because refrigeration can sometimes turn the leaves black or slimy.

Trim the basil stalks and keep them in a jar of water in your kitchen to get the most use out of your harvest. You can remove fresh basil from the bunch and store it for later use if you prefer.

Does Basil Droop At Night?

The sensitivity of basil to temperature changes is well-known. When the temperature drops at night, the basil responds by dropping its leaves.

Before showing black spots on their leaves, basil leaves will begin to droop in the cooler months.

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What Can You Do With Old Basil?

You can make classic pesto with old basil and use it in all of your favorite sauces and dips.

Some people prefer to preserve dried basil leaves by crushing them as a condiment in their meals.

How Do I Know When To Pick Basil?

During the basil’s juiciness peak, harvest the leaves 6 to 8 inches tall.

More leaves will grow if you pick them up early in the morning and harvest them regularly.

Why Are My Basil Leaves Turning Black?

There are several reasons why basil plants turn black on their leaves. These reasons include mites, aphids, bacteria, fungi, and viruses. 

Examine your basil plants. Remove any insects and check for leaves with yellowing or small holes in them. Use a magnifying glass to examine the undersides of leaves to look for the presence of white powdery matter.

Can We Still Eat Basil That Has A Few Black Areas?

It depends on the type of black spot. Bacteria or viruses can cause black spots, so be sure to cut out any damaged leaves and wash the soil. If the spots are not damaged, it is best to let them be.

Are The Leaves And Stems Of Your Basil Plant Turning Black?

The most common cause for basil leaves turning black is mold. It is best to cut off the affected area and discard it when this happens. You can also try washing the affected leaves and stems with water. Be sure to dry the plant thoroughly afterward.

If you notice discoloration on the stems, this may be caused by something you’re applying to your plants (such as fertilizer, soap, or other products). Try removing the affected area and washing the stems and leaves well with clean water.

Should You Change The Soil Of Black Spot Basil?

Whether or not it’s a good idea to change the soil where the basil is growing in the garden is impossible without more research.

If your plants are not starting to grow or stunted in size, it may be a good time to replace the plant’s soil.

Why Does Basil Turn Black After Washing?

Basil is a shared kitchen herb found year-round at grocery stores. It is used for its flavor and aroma in sauces, soups, pasta, and pizzas. Basil leaves, like other fresh herbs, are highly perishable. 

Basil, particularly in its raw state, contains a chemical that prevents storing it for too long. This chemical helps to protect the leaves from insects and other pests.

Therefore, basil leaves turn black due to a fungus called Alternaria. The most common causes are fungal diseases, pests, and poor growing conditions. However, other causes can include nutrient deficiencies, herbicide damage, and frost damage.

It can cause severe damage to plants, fruits, and vegetables. There is no known cure for this fungus, so it is important to take preventative measures to protect your basil plants.

Ensure your basil plant is getting the right amount of water, air circulation, sunlight, and drainage to get the most out of it.

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