6 Reasons Why Basil Leaves Turn Brown

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Basil is a fragrant herb that is often used to flavor dishes. If you’ve ever had pizza with some aromatic green leaves scattered on top or a pasta dish with pesto sauce, you’ve eaten basil. This sweet-smelling herb is wildly popular, not just because of the delicious flavor it brings, but also because it is one of the easiest herbs to grow. Just like other plants, however, basil requires the right amount of care to ensure its growth. In case your basil leaves turn brown, here are some quick steps to remedy it.

While basil leaves are easy to care for, they are also sensitive plants. If you ever find your basil leaves turning brown or yellow, you need to find which of the following might be the cause: lack of sunlight, wrong temperature, over-water or under-watering, soil diseases, or pest problems. Identifying the cause will help you treat your plant quickly so it can go back to its healthy, thriving state.

About basil plants

Basil, also known as Ocimum basilicum, is one of the most popular herbs in America. It is a member of the mint family and can be grown both indoors and outdoors and used for various dishes. Basil is an annual plant, meaning they flower and die in one season and will bloom all season until frost. If you want basil again the following year, you’ll have to plant them again. Sometimes basil plants even go from seed to harvest in only 3 to 4 weeks. If it’s your first time to plant herbs or grow a garden, growing basil is something that you should try.

Growing basil in a garden

It’s easy to grow basil in your home garden. As long as you’ve got full sun and soil that is moist, rich, and well-drained, your basil plants will be in optimum condition. You can even add a healthy amount of organic nutrients when you put compost, cottonseed meal, or blood meal to the soil.

The earliest time to start planting basil is around two weeks after the last frost—the warmer the better. Seeds can even be germinated indoors while you are waiting for the frost to pass, and then transferred outdoors in the spring. When you transfer the seeds to your garden, find a place that has plenty of sunlight and make sure that they are spaced at least 12-18 inches apart. That way, you leave lots of room for growth.

Outdoor basil plants require at least six hours of sun per day and an inch of water per week. If you live in a place with intense midday heat, try to find a way to give your basil plants some shade during the hottest hour of the day.

There’s no specific time to harvest basil. The idea is to grab a few leaves as you need them. Make sure you cut the stems and not pull the leaves. The more you harvest basil, the more it grows. If properly cared for, garden-grown basil plants can last for as long as 6 months.

Growing basil in pots

Woman cutting basil leaves off a plant growing in the kitchen
Basil does quite well indoors, and can be placed near a window in convenient distance to your kitchen countertop.

If you don’t have a garden or plot of land where you can grow your basil plants, there’s no need to worry as basil also grows well in pots, provided that your pot is large. Small pots easily dry when the weather turns hot and they will often need water, both of which can harm a growing basil plant. As basil plants thrive in well-drained soil, your soil must be fresh and spongy and your pot must have a drainage hole to prevent your soil from becoming soggy. It’s best to water sparingly, so feel your soil first before watering it. If the soil still feels moist, don’t water it first.

Just like basil plants grown in the garden, basil that is grown in a pot also requires at least six hours of direct sunlight. You can place them on the window sill in the morning so they can soak a lot of the morning sun and then put them in a shady place when the sun becomes too hot.

Causes of basil leaves turning brown and/or curling

Even while basil is a plant that is relatively easy to grow, you still need to make sure you are doing the right steps as you care for it. Basil plants are not high-maintenance, but they are sensitive to their surroundings. Watch out for your basil leaves turning brown which could be a sign that something is wrong.

Here are some of the most popular causes of basil leaves turning brown and the solutions you can apply to make sure they go back to their thriving, healthy state:

#1 Lack of sunlight

Basil plants love the sun and are extremely sensitive to cold. If the leaves of your basil plant are turning brown, it could mean that they are not receiving enough sun. It’s important for basil plants to get at least six to eight hours of full or partial sunlight. It’s also important to plant basil in a very sunny but shady spot. You want to make sure that your basil is in a place where it can receive plenty of sun without the chill of the wind.

Even if basil plants can grow on the windowsill, the part that is not turned toward the window could suffer from not getting enough direct sunlight. If you are in a place that has little or no natural light, you will need to make sure your basil plant is exposed to at least 12 hours of artificial light each day.

How to fix – Check if your basil plant leaves are curling and turning yellow and if the plant has longer stems but fewer leaves. If that is the case, it means that your basil plant lacks sun.

Make sure your basil plant has not been planted outside unless you are sure that the danger of frost is over. If your basil plant is potted, make sure to turn it on the window sill so all sides are exposed to the sun. You can also opt to move your plant to a sunnier position in your garden or around your house.

#2 Too hot, too cold

While they are generally easy to grow and cultivate, basil plants are sensitive to abrupt and abnormal weather changes. If the temperature suddenly drops or spikes, resulting in your basil leaves turning brown or new leaves deforming, the growth of a basil plant may come to a stop.

Because it is an herb that is traditionally grown in tropical climates, basil does not handle cold temperatures very well and may even wither and die if the temperature drops below 50°F. If you live in a place where nighttime temperatures drop suddenly and drastically, there’s a chance your basil plant might not survive that.

At the same time, if it is too hot, a basil plant will shrivel up and die. Basil plants must be exposed to as much direct sunlight as possible, but if they are very young plants, they are also in danger of suffering from too much sun.

How to fix – A basil plant with leaves that are browning or deforming can still be salvaged. If your basil plant is out in the garden and you think that it is still in danger of too much cold, you can move it back indoors or to a new part of your garden where the sun reaches better and the soil is warmer. If you feel like the heat is the cause, find a way to give your garden-planted basil a nice shade or opt to expose your potted basil to a less-intense afternoon sun.

#3 Too wet, too dry

One of the common mistakes when it comes to growing basil is watering. In some instances, you might find that you are watering your potted basil too much, something that happens frequently with indoor plants because moisture doesn’t evaporate as quickly indoors as they do outdoors.

In other instances, if you keep your potted basil plants outdoors where water evaporates faster and doesn’t accumulate in the soil for a long period, you might be underwatering them.

How to fix – If you think you might be overwatering your basil, the first thing you should do is to inspect the roots of your plant. If a large part of the roots have gone soft and mushy and are colored brown, it means that the plant has rotted. If the damage is minimal, you can still save your basil plant by getting it and replanting it in new, dry soil. Before you water it, check to see if the soil is dry to the touch.

If you see that the leaves of your basil plant are curling, shrinking, and drying out, there’s a chance that you are underwatering your basil plant. Another key indicator is the taste and smell of the leaves, as they will become bitter and pungent.

If your plant is exposed to a lot of sun, such as on a window with direct sunlight, you will need to give it sufficient water to keep the plant moist. Don’t keep a strict schedule when it comes to watering your plant. Instead, check first to make sure that the first 1 to 2 inches of the soil are dry before watering so you don’t make a mistake and end up drowning your basil.

#4 Improper soil and fertilizer

Basil thrives in average soil that isn’t rich in organic matter. The soil where you plant your basil must be slightly acidic and well-drained. On the other hand, if your soil is highly acidic, there’s also a chance that it will burn the basil and cause it to brown and wilt and its leaves to curl. This can also be a result of improper fertilization.

How to fix – If your basil has yellow or discovered leaves and very slow growth, it’s possible that your plant may be getting enough light, but may not have enough nutrients. When it comes to the soil, sandy loam is often recommended because it will prevent fungal problems such as the roots of your basil rotting. If you want to use fertilizer for your basil, use an organic one, such as compost tea. You can also opt to use vermicompost or shellfish or any other soil amendments to give the soil much-needed nitrogen and other essential minerals.

If you’re growing basil the whole year round in pots, remember to repot it every few months. Soil becomes stagnant after being left in the pot for a long time and loses its nutrients. Make sure you don’t change pots too much, though, as this can shock the basil’s stability.

#5 Diseases

Basil, just like other plants, can also be subject to various kinds of plant diseases. A couple of the most common fatal diseases to a basil plant the Fusarium Wilt and the damping-off which are caused by some species of fungi. These diseases can make your basil leaves turn brown and curl and even darken some parts of the stem.

How to fix – Unfortunately, there’s no cure for fusarium wilt, and plants that have been infected with it must be destroyed. Damping-off can be treated with fungicides. To avoid either of these diseases, refrain from overwatering your plants so the soggy soil doesn’t encourage fungus growth. Try to also leave a good amount of space in between your plants so they aren’t over-crowded. If you are growing basil for the first time, be careful where you buy your soil, seeds, and plants.

#6 Pest problems

In general, basil plants don’t have that many pest problems. Nevertheless, an occasional insect—such as spider mites, thrips, aphids, and the like—might still attack the herb by sucking the juices and causing the leaves to brown and curl. While they don’t do much damage to the plant, it’s still better to keep them under control so your basil continues to be in its healthy state.

How to fix – Inspect your plant regularly and check for the presence of pests. Look at both sides of the leaves and along the stems and see if the leaves have turned brown or yellow entirely or may have developed yellow spots in an irregular pattern. To ward off the occasional insect, you can opt to use predatory insects (such as ladybugs and lacewings) as a way to keep the pests under control. You can also opt to spray the basil with horticultural oil or insecticidal soap.