Basil Leaves Turning Black On Plant And After Picking? (Fix It Now!)
Basil is a popular herb used in kitchens around the world, known for its intense flavor and sweet smell. Although originally found in tropical Africa and Southeast Asia, this member of the mint family has given birth to several varieties that we use worldwide. Sweet basil, or Genovese basil, is more commonly used in our kitchens today. Basil is easy to grow in your home or garden, but beware of any basil leaves turning black.
There are many reasons why your basil could be turning black. Basil plants are fragile; both underwatering and overwatering will kill your plant. But water isn’t the only culprit– basil is also susceptible to fungal infections and downy mildew. And if that doesn’t seem like enough, pests like aphids and fungus gnats can quickly kill your basil.
To keep your basil leaves from turning black, keep the soil evenly moist. Don’t let the soil get too dry. When watering your basil plant, allow the water to soak completely into the soil before adding more to avoid drowning the plant. To combat fungal infections and bacterial leaf spots, make sure your basil has plenty of air circulation and adequate drainage. Once you’ve picked your basil, keep it fresh by storing the bunch in a jar with water. Cover and refrigerate
Common Causes and Their Solutions
Black Leaves Caused by Overwatering
With delicate plants like basil, there is a fine line between overwatering your plant and underwatering. Basil that is overwatered will begin to wilt before turning yellow and then brown. If you suspect that your basil plant is overwatered, check the soil. An overwatered plant will have saturated soil.
Ensure that the soil is evenly moist and not soggy. The roots of your basil need room to breathe! If you saturate the roots with water, the roots may rot. Check that the soil is porous and will allow the water to drain completely.
Solution: Stop watering immediately and move the plant into a sunny and warm place for the soil to dry.
Black Leaves Caused by Underwatering
While the signs of underwatering and overwatering can look very similar, an underwatered basil will have leaves that are dry and crispy. Underwatered basil will also have wilting leaves, but the soil will be dry. Fortunately, basil plants can recover from underwatering much easier than overwatering.
Solution: When your basil plant starts to droop, water generously. Allow the soil to soak up the water before adding more. Take care not to get any basil leaves wet, as additional moisture could produce mildew. After a couple of hours, you should see your basil plant perk up.
Black Leaves Caused by Diseases
Basil is particularly prone to fungal infections. Downy mildew is a common cause of black spots on basil plants. If left unchecked, downy mildew can lead to a bacterial leaf spot caused by Pseudomonas cichorii. It only takes one bacterial leaf to kill your entire basil plant.
The fungus Peronospora belbahrii is responsible for downy mildew, for which there is no cure. The spores arrive via water droplets or air and quickly spread. Warm or humid conditions speed up the spread. Black lesions on the leaf surface are a sure sign of downy mildew. Check underneath the leaf for dark growth. In high humidity, these affected areas may turn black.
Solution: Remove any infected leaves, including those that have already fallen from your plant. Destroy the infected materials to prevent the spread to healthy plants. You can also treat black leaf spots regularly with fungicide.
Black Leaves Caused by Pests
Although basil’s pungent profile makes it a natural repellent to flies and mosquitoes, basil is susceptible to several pests like Japanese beetles, fungus gnats, slugs, and aphids. Japanese beetles are rampant for a month in the summer, but luckily you can pick these bugs off with your hands.
Solution: Pick off larger bugs such as beetles and deter smaller pests with insecticidal soap or spray. You can easily knock whiteflies, spider mites, and aphids off your basil leaves with a spray from the water hose, but make sure to do this early in the day to avoid waterlogging the leaves.
Black Leaves Caused by Poor Nutrition
Black spots on basil could be due to poor nutrition in your plant’s soil. Too much or too little nitrogen in your fertilizer is a common culprit. Although an imbalance of nutrients could be difficult to diagnose, always support your plants with an organic fertilizer.
Solution: Use quality organic compost instead of commercial fertilizer.
Black Leaves Caused by Frost
Basil is very sensitive to temperature. An unexpected frost can shock the leaf edges and cause the plant to die. Temperatures below 50 degrees can damage your basil plant and hamper its future growth.
Solution: To protect your basil plant from the elements, water your basil thoroughly. Not only does wet soil stay warmer than dry soil, but damp soil absorbs more heat from the sun. Mulch and secure the roots. If you are expecting a sudden cold snap, consider covering your basil with plastic sheeting.
Caring For Basil
Most basil plants are annuals, meaning that they don’t automatically come back the following year. Since basil plants are native to tropical climates, they do best in the sun and heat. Basil plants need 6-8 hours of sun each day. Water the soil evenly and ensure that the soil is draining well. Adequate air circulation is vital in keeping the leaves free of fungi and pests.
Basil can be grown indoors or outdoors. Basil plants flourish in containers and raised garden beds which allow for better drainage. If planting in containers, make sure that you have left enough space between each basil plant. Planting indoors and then transporting outside enables you to plant basil weeks before the last frost, rather than waiting until after the last spring frost. Protecting your basil plant from subfreezing temperatures will keep the leaves from turning brown or black.
Preserving Your Harvested Basil
To keep your basil leaves from turning black once you’ve picked them, first wash and dry your basil. Store the basil in a container of water at room temperature. Basil will root in water, so it’s a convenient way to always have it on hand!
If you find yourself with too much basil, you can freeze your basil leaves, similar to cilantro. After you’ve washed and dried them, arrange the basil on a cooking sheet and set it in the freezer for 2 hours. You can cook with whole frozen basil leaves much the same as fresh basil leaves.
Types of Basil
By some estimates, there are as many as 150 species, although most of the basil we eat is a cultivar of O. basilicum or sweet basil. Sweet basil is the traditional basil, easily found at most grocery stores. Sweet basil is characterized by dark, shiny leaves and a pungent smell. If your recipe does not specify, it is most likely calling for sweet basil. Sweet basil is used interchangeably with Genovese basil.
There are several types of basil in addition to sweet basil or Genovese basil. Thai Sweet Basil, Purple Basil, Dark Opal Basil, Lemon Basil, Lime Basil, Green Ruffles, Holy Basil, and Cinnamon Basil are becoming popular garden herbs due to their intense flavor profiles.
We’ve been using basil has in cooking for centuries! Take a look at some of your favorite foods– basil is in marinades, pesto, salads, and pizzas. And if you don’t feel like cooking, you’re in luck. Basil makes an excellent companion to fruits like watermelon, strawberries, and tomatoes.
In addition to being a natural anti-inflammatory, basil promotes heart health and good circulation. Basil has been used to treat upset stomach, loss of appetite, intestinal gas, headaches, and even ear infections.
Can I bring my basil plant back to life?
There are a couple of things you can do to revive your basil plant. If your basil plant is wilting, first give it a thorough watering. Then, let the soil completely soak up the water before adding more. Move the plant into the shade to avoid heat stress, and give your basil plant a few hours to perk up. Finally, Clip away any basil leaves that are unsalvageable to avoid mildew.
What is the best way to store basil?
Like other herbs, basil can be picked, washed, dried, wrapped in a paper towel, and stored in the refrigerator for up to 3 days. But since refrigeration can sometimes cause basil leaves to turn black or slimy, it lasts the longest at room temperature. To get the most out of your harvested basil, trim the stalks and store them in a jar of water in your kitchen. Pick fresh basil from the bunch at your leisure or cover for later use.
Is it safe to eat basil that has turned black?
Basil with a few brown spots should be safe to eat, but try to avoid it. Dark spots on basil could be a sign of pests, and may have a slimy consistency and a bitter taste.
To best care for your basil plant, make sure that your basil is getting the right amount of water, air circulation, sunlight, and drainage. Proper care of your basil plant will protect it against pests, disease, mildew, and anything else that might be turning your leaves black.
HK Sloan is a freelance writer currently covering DIY Home Improvement, Health, and Lifestyle. Sloan is passionate about improving situations for less, whether it be working on mind, body, or home.
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