Skip to Content

Why Does My Basil Have Black Spots – Top 4 Reasons!

Sharing is caring!

Growing vegetables and herbs at home is a very fulfilling task. You have your little kitchen garden, and you can pick any herb or veggie you want, fresh out of the garden, anytime you want. Basil is one of the most commonly grown herbs in homes.

It has a bright green appearance and adds freshness to your garden. But if you have recently noticed little black spots on the basil leaves, you could be left wondering – why does my basil have black spots?

You don’t need to panic just yet. Black spots do not always mean the end of your plant. You can take some steps to revive it or save it. However, first, you must know all the reasons behind the black spots to act accordingly. Keep reading, and we will reveal the answer to your query – why does my basil have black spots?   

Why Does My Basil Have Black Spots 1
Black spots on basil. What is this and what can I do? – via Reddit

Why Does My Basil Have Black Spots?

Basil comes from the mint family, and conditions similar to a tropical environment are best for this plant. So, it grows best in warm temperatures and during the summer season. Nowadays, basil is grown in almost all places around the world. You can grow it in a pot inside the house or plant it in your garden, directly in the soil.  

Despite its easy-growing nature, certain conditions can cause black spots to appear on it. Some of the main reasons for these black spots include extreme cold, fungal, bacterial, pest attacks, nutrition issues, and more. Let’s find out all the reasons to answer your question – why does my basil have black spots?

#1 Fungal and Bacterial Infections

Fungal and bacterial infections are one of the common causes of the appearance of black spots on a basil plant. With these infections, the black spots can appear anywhere on the leaf.

You may spot them on the edge, tip, in the middle, or on the underside of the leaves as well. Usually, a fungal attack starts from the bottom of the leaf, and the spots start appearing all over once the infection spreads.

Pseudomonas Cichorii is a bacterial infection that can take over your basil plant. The black spots will be large and will soon become dry, causing holes to form on the leaf. You need to throw away the affected leaves here.

Cercospora leaf spot is a fungal infection that usually occurs when the plant is left in a moist, cold, and dark environment. The black spots, in this case, will be large and round as well. You may also notice a slight yellow color around the black spot. After some days, the black spots may develop a slightly gray color in the center, become dry, and form holes in the leaves.

Mildew is a parasite that usually invades the indoor basil plants and is one of the most common reasons black spots form on the basil leaves. This, too, attacks the plant in confined, dark, wet, and cold environments.

It is hard to spot mildew because the black spots here look like dust or dirt. You will be able to see it on the bottom of the leaf only. Mildew spreads very easily to other plants and can cause the discoloration of the leaves.   

Why Does My Basil Have Black Spots 2
What are these black spots on my basil? What should I do? – via Reddit

#2 Pest Attack

Besides fungi and bacteria, pests can also attack the basil plants to form black spots. Sometimes a pest infestation looks like a fungal attack, so check for pests to be sure. The black spots formed by a pest attack are tiny and large numbers. The color may be more grayish-black than jet black.

To avoid confusing pest attacks with fungal attacks, check the symptoms thoroughly and try to find the pests living on the leaves. Also, look for white/yellow coloring around the black spots. Thrips, aphids, spider mites, and whiteflies are some of the pests that may invade and eat away your basil plant.  

In case of pests, you might have to remove the leaves affected by these. You could also use neem oil or a good pesticide to tackle the issue.

HARRIS Neem Oil, 100% Cold Pressed and Unrefined Concentrate for Plant Spray, High Azadirachtin Content, 12oz
  • 100% Cold Pressed & Unrefined - All natural with absolutely no chemicals or additives included to ensure that the neem oil retains its original composition
  • Cosmetic grade - The oil is high in antioxidant compounds that soothe the skin
  • Organic gardening uses - used in organic gardening to keep plants looking healthy
  • Mix with lotions or shampoos - Antioxidants, vitamins and essential fatty acids provide nourishment for hair, nails and skin
  • Note: This product is not registered with the EPA as an insecticide, Harris cannot support any claims that might be made by 3rd parties
Monterey LG6150 Garden Insect Spray, Insecticide & Pesticide with Spinosad Concentrate, 16 oz
  • Fast acting and odorless - Monterey insect Killer is a bacterial product produced by fermentation which rapidly treats plants and does not produce odors.
  • Controls many insects - the insect treatment Spray controls caterpillars, leafminers, codling moth, tent caterpillars, gypsy moth, trips, borers, fire ants, and more.
  • Variety of uses - this pest control can be used on outdoor ornamentals, lawns, vegetables, and also broadleaf weeds.
  • Easy spray application - this CSI alternative product may be applied with a trigger sprayer, hand-held, backpack, or hose-end Sprayers. Carefully read the label directions before use for optimal application.
  • Organic gardening - the active ingredient in our bug Killer spray is a natural bacteria called spinosad, which is the newest agricultural chemistry to be introduced. Approved For organic gardening, our product is safe for use around people and pets.

#3 Extreme Cold

Basil plants do not fare well in colder temperatures. They are native to tropical areas and need warm to hot weather to thrive. If the basil plant is exposed to sudden cold or chilly weather, it can develop many health issues like the growth may become stunted, it may become susceptible to pest attacks, and develop black spots.

Black spots formed due to cold weather appear on the surface of the leaves, on the edges, and on the tips as well. Sometimes the weather may suddenly turn cold during the spring season sending shocks to the basil plant.

If your basil is planted outside, keep checking the forecast to know what to expect. If there are expected chilly winds, frost, or if the weather is generally moving towards winters, you need to make proper arrangements for your basil.

You can cover the plant with a bell jar or a tent to keep it warm. Another way is to trim the leaves and store them in your freezer before the weather turns. If you move your plant from a warm indoor place to an outdoor location, introduce it gradually, as the outside may be colder than the inside.

#4 Issues with Nutrition

Lack of proper nutrition can also cause black spots on the basil leaves. Not enough nitrogen is the more common reason for the plant reacting this way. In this case, you can go for a good nitrogen-based fertilizer that is safe for the herbs and occasionally used in the soil of the basil plant.


When you have your heart and soul invested in growing a plant, it can be difficult to see it suffer from diseases and go to waste. But keep in mind that sometimes the only solution is to throw away the plant to prevent the infection from spreading. A rotten plant may not be able to survive.

It is better to spot the condition in its early stages to be dealt with efficiently. However, you must not worry too much as the plant is not always dead. In most mild cases, you will be able to revive it. Just keep giving the right conditions, and don’t lose hope.

I hope this answers your question – why does my basil have black spots? If you have any tips, share them with fellow gardeners.