Basil (Ocimum basilicum) is a versatile herb commonly used in cooking.
Gardeners often use this herb, commonly known as garden-fresh parsley, in their gardens to add a strong, pungent flavor to their dishes, as well as to garnish and decorate salads, soups, and other recipes.
While Basil is generally easy to grow, sometimes the leaves can turn yellow. This can be due to several factors, including diseases, pests, or poor growing conditions.
If your Basil leaves turn yellow, here are 10 possible causes and solutions.
What Causes Basil Leaves to Turn Yellow and How To Fix It
The growth of herbs in the home garden is a great way to add freshness and flavor to dishes, as they require minimal care and can be harvested regularly to ensure steady growth of the plants.
Basil leaves are usually green, but if they turn yellow, it can be due to several reasons.
A yellowing of the leaves can be a sign of overwatering, nutrient deficiencies, or too much direct sunlight, all of which can be detrimental to the health of the plants.
Here are some common causes of yellowing basil leaves and what you can do about them:
1. Too Much Water
Overwatering Basil plants is a common problem, as the leaves will begin to turn yellow and fall off.
This problem is typically caused by too much water in the soil, which can drown the roots and prevent the plant from getting the oxygen it needs, leading to the roots becoming infected with fungi and bacteria, resulting in root rot.
If your plant is wilting and the leaves turn yellow, check the soil to see if it’s too wet.
The soil should be moist but not soggy.
How to Properly Adjust Watering
If your Basil is wilting and the leaves turn yellow, it’s likely because it is getting too much water.
You’ll need to let the soil dry out completely before watering again to fix this problem.
You can also try using a well-draining potting mix to help prevent overwatering in the future.
This herb needs to be watered regularly, but you should allow the soil to dry out between waterings.
To check if your plant needs water, insert your finger into the soil up to the first joint; if the soil is dry, it’s time to water, but if it’s still damp, wait a few days before watering again.
If the soil is too wet, try increasing the time between waterings or choose a pot with drainage holes to help improve drainage.
2. Not Enough Water
Basil leaves can turn yellow for several reasons, but one of the most common causes is a lack of water.
When plants don’t receive enough water, their leaves will turn yellow and eventually brown and wilt.
The stems of Basil plants are particularly vulnerable to drought, as even a small amount of dryness can cause their leaves to turn yellow and become brittle, making them more susceptible to breakage and damage.
Basil needs to be watered regularly, especially during hot weather.
Correcting Watering Practices
The good news is that you can easily prevent this by carefully and consistently watering your basil, ensuring it receives sufficient water.
If you notice the Basil leaves turning yellow, increase the frequency and amount of water you’re providing to the plant.
To ensure the plant stays healthy, it’s important to check the soil at the bottom of the pot to make sure it’s not too dry before watering. It should be watered at least once a week and more often during hot weather.
3. Lack of Light
Basil is a sun-loving plant that needs at least 6 hours of sunlight per day to thrive.
If plants don’t get enough light, their leaves will turn yellow.
This is because Basil lacks chlorophyll, which gives plants their green color.
Improving Light Conditions
To fix this problem, move your plant to a brighter location.
If you’re growing Basil indoors, place it near south-facing windows where it will get the most sunlight.
They need at least 6 hours of sunlight per day, so ensure the plant is getting enough light.
However, too much direct sunlight can also cause leaves to turn yellow.
4. Too Much Light
While Basil needs a lot of light to grow, too much sunlight can harm the plant.
If plants are exposed to too much direct sunlight, their leaves will turn yellow.
This is because the plant is producing too much chlorophyll in an attempt to protect itself from the sun.
Balancing Sunlight Exposure
If your Basil plant is getting too much sunlight, move it to a shadier location.
Growing Basil indoors requires a shadier location, such as near an east or west-facing window where it will get indirect sunlight, as too much direct sunlight can cause the leaves to become scorched and the plant to wilt in the shade.
These plants need at least 6 hours of sunlight per day, so ensure the plant isn’t getting too much or too little light.
5. Nutrient Deficiencies
Basil plants can also suffer from nutrient deficiencies, which can cause their leaves to turn yellow.
The most common nutrient deficiency is nitrogen, but the plant can also lack other essential nutrients like phosphorus and potassium.
Several factors, including poor soil quality, incorrect fertilizer ratios, and inadequate watering, can cause a nutrient deficiency.
Rectifying Nutrient Imbalance
If you suspect your Basil is suffering from a nutrient deficiency, the best action is to get a soil test. This will help you determine which nutrients are lacking and how to amend the soil best.
You can also try using a fertilizer high in nitrogen, phosphorus, and potassium to help correct the nutrient deficiency.
They must be fertilized every 2-4 weeks during the growing season.
6. Overfertilization
While Basil plants need to be fertilized regularly, it’s important not to overdo it.
Overfertilizing these plants can cause their leaves to turn yellow or brown. This is because the plant is getting too much nitrogen, which causes the leaves to turn yellow.
It can also cause the plant’s roots to burn, leading to leaves turning brown and wilting.
Proper Fertilization Guidelines
If you think your Basil has been overfertilized, flush the soil with water to remove any excess fertilizer.
You can also try moving the plant to a new container with fresh, unfertilized soil.
These herbs should be fertilized every 2-4 weeks during the growing season.
7. Pest Infestation
Basil plants can also be affected by pests, which can cause their leaves to turn yellow or brown.
The most common pests that affect these plants are aphids, whiteflies, and spider mites.
These pests suck the sap from plants, which can weaken the plant and cause its leaves to turn yellow.
Pest infestations can also lead to Basil leaves turning brown and wilting.
Effective Pest Management
If you think your plant has a pest infestation, the best course of action is to treat the plant with neem oil or an Insecticidal soap.
You can also try to remove the insects by hand. Use a cotton swab or a Q-tip dipped in rubbing alcohol to kill the pests.
To ensure the removal of all pests from your plant, use a strong blast of water from a hose and make sure to pay special attention to the undersides of the leaves, as this is often where the pests hide.
8. Cold Weather
Basil plants are native to tropical climates and can’t tolerate cold weather.
If they are exposed to temperatures below 50°F, their leaves will turn yellow. This is because the plant is shocked and trying to protect itself from the cold.
When the temperature drops below 50°F (10°C), it is important to bring them indoors or cover them up to protect them from the cold, as they are not frost tolerant and may suffer damage if exposed to temperatures below this threshold.
Protecting Basil from Cold
Bring it indoors and place it in a warm, sunny location if your Basil is exposed to cold weather.
Cover it with a frost blanket or burlap sack to protect it from the cold if you can’t bring the plant inside.
You should keep them above 50°F at all times.
9. Basil Downy Mildew
Basil downy mildew is indeed a fungal disease that commonly affects Basil plants.
It is caused by the pathogen Peronospora belbahrii and is often characterized by the appearance of yellowing leaves.
As the disease progresses, the affected leaves may develop dark, purplish blotches and eventually turn brown or black.
Other symptoms may include stunted growth, curling of leaves, and a white, fluffy growth on the undersides of leaves.
If left untreated, downy mildew can cause defoliation and eventual plant death.
Preventing and Treating Downy Mildew
If your plant has downy mildew, the best action is to remove all affected leaves.
Destroy any infected leaves that you find to prevent the fungal infection from spreading.
Fungicides and cultural practices such as proper plant spacing, adequate air circulation, and watering at the base of the plant can help control the spread of the disease.
Additionally, planting resistant basil varieties can also be an effective preventive measure.
10. Potting Soil Issues
Basil plants need well-draining, nutrient-rich soil to thrive.
If they are grown in potting soil that’s too dense or doesn’t have enough nutrients, their leaves can turn yellow.
The best way to avoid this issue is to use a high-quality potting mix for Basil plants.
You can also add some organic matter to the soil to improve its drainage and nutrient content.
How to Manage Issues with Potting Soil
If your plant is grown in potting soil that’s too dense or doesn’t have enough nutrients, repot the plant in a high-quality potting mix.
You can also add some organic matter, such as compost, to the soil to improve its drainage and nutrient content.
Basil plants need well-draining, nutrient-rich soil to thrive, so provide them with the best growing conditions possible.
11. Overcrowding
Basil plants need room to grow and should be planted in individual pots.
When plants in an overcrowded environment don’t have enough air circulation, they can become stressed, and their leaves can start to turn yellow due to the competition for space, light, and nutrients.
Plants that are overcrowded will also produce fewer leaves and flowers.
How to Address Overcrowding
If your Basil plants are overcrowded, repot them in individual pots.
Be sure to provide each plant with enough space to grow.
Plants need room to breathe and should be planted in separate pots.
12. Transplant Shock
Basil plants can go into shock when they are transplanted. This is a normal reaction and nothing to worry about.
When a plant is transplanted, it may experience stress due to changes in its environment, such as changes in temperature, light levels, or soil conditions.
As a result, the plant may exhibit symptoms of shock, including yellowing leaves. However, with proper care and adjustments to the new conditions, the plant should recover and resume healthy growth.
Helping Basil Recover from Transplanting
If your Basil is experiencing transplant shock, give it time to adjust to its new environment.
Plants need time to acclimate to their new surroundings and usually recover within a few days.
Be sure to water the plant regularly and keep it in a warm, sunny location.
13. Natural Leaf Yellowing
It’s normal for Basil leaves to turn yellow as they age.
Plants always produce new leaves, and the older leaves will eventually turn yellow and die off.
This is a natural process and nothing to worry about. They will continue to produce new leaves as long as they are healthy and happy.
Dealing with Natural Leaf Yellowing
There’s no need to fix yellowing leaves due to age.
Just remove the affected leaves and dispose of them.
Basil plants will continue to produce new leaves, so don’t worry about the plant losing its foliage.
Dealing with Yellow Basil Leaves With Brown Spots
Basil leaves can turn yellow with brown spots due to several different reasons.
Basil downy mildew, nutrient deficiencies, and herbicide damage are common causes of the plant turning yellow with brown spots.
When diagnosing the problem, it’s essential to look for other symptoms that can help narrow down the cause.
- Due to herbicide damage, leaves turning yellow with brown spots will also have a burnt or scorched appearance.
- Leaves turning yellow with brown spots due to nutrient deficiencies often have pale green or yellowish-green leaves.
- Downy mildew will cause the leaves to turn yellow and brown and have a powdery or fuzzy appearance.
How to Treat Yellowing Basil Leaves and Curling
A variety of factors can cause basil leaves to yellow and curl.
Basil downy mildew, heat stress, and pest infestations are common causes of yellow Basil leaves and curling.
When diagnosing the problem, it’s essential to look for other symptoms that can help narrow down the cause.
- Leaves turning yellow and curling due to downy mildew will also have a powdery or fuzzy appearance.
- Plants experiencing heat stress will often have wilted or drooping leaves.
- Leaves infested with pests will have small holes or chewed edges.
Handling Basil Yellow Leaves With Black Spots
Basil leaves can turn yellow with black spots for several different reasons.
It is a very sensitive plant; even minor environmental changes can cause eaves to turn yellow with black spots.
The most common reason for yellow leaves with black spots is a lack of water.
Leaves will also turn yellow if the plant is not receiving enough water or if it is being overwatered.
Should I Remove Yellow Leaves From Basil Plant?
If you have a basil plant, you may notice that the leaves turn yellow. While this is a common problem, it can be frustrating to see your plant suffer.
So, should you remove yellow leaves from basil plants?
The answer is yes and no. If the leaves are only slightly yellow, you can still use them for cooking.
However, if the leaves are very yellow or starting to brown, it is best to remove them. This will help the plant focus its energy on producing healthy new leaves.
If you decide to remove yellowing leaves, be sure to do so gently. These leaves are delicate and can easily be damaged.
Use sharp scissors or pruning shears to make clean cuts. These herbs are generally very resilient, so don’t be afraid to trim them back.
Final Thoughts
With the right ingredients, such as adequate sunlight, nutrient-rich soil, regular watering, and proper care and attention, you can provide your basil plant with the essential elements it needs to thrive.
Soon enough, you will be rewarded with a lush, green, and healthy plant.
However, basil can turn yellow for a variety of reasons, most often due to a lack of nutrients or excessive watering.
They also require well-draining, nutrient-rich soil to thrive.
If your plant’s leaves turn yellow, try one of the solutions mentioned above.
With some care and attention, you can bring your basil plant back to its green and healthy state in no time.
