Basil Plant Turning Yellow or Brown? (Why and What to Do)

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Basil is an herb that is used in many different areas of life. For some people, it is almost entirely used in cooking to make dishes taste more flavorful, while in other cases, basil can be used as a natural remedy for health conditions.

While you can often find basil in the stores, many people find it much more beneficial to plant and care for the basil itself. Not only does this mean that you have a regular supply of fresh basil whenever you need it, but this also means that you get the enjoyment of caring for plants, which is something that most people can appreciate.

With that being said, this means that you will also need to be aware of how you can care for the plant and what kind of requirements it has. All different plants require different kinds of care to ensure that they can grow and thrive under your care, and the basil plant is no different in this regard.

Caring for basil is relatively easy as it is a low-maintenance plant. Typically, as long as you leave it in a location that gets an adequate amount of sunlight and you water it every so often, you will have a thriving basil plant that you can make use of; however, there are times when you may feel at more of a loss as to how you should care for your basil plant.

For example, there may come a time when you look over at your basil plant and the leaves are turning another color. Basil plants should keep their bright green leaves for as long as they are growing, and the vivid green leaves are a sign of good health in the plant, so when the leaves start turning another color, it is a good indication that there is something going on that is affecting the plant’s health.

When caring for plants, the general consensus is that the color of the leaves and the pattern that they develop will give you a good indication of what is going on with the plant’s health, and this applies to basil as well.

For instance, if the leaves are simply turning yellow or brown, that is an indication of a lack of water or nutrients, whereas if the leaves are only turning yellow around the veins, that might indicate a potassium deficiency.

The first step to caring for a basil plant with discolored leaves is to determine what the leaves are trying to tell you so that you know what steps to take to make the problem better.

Why Do Basil Leaves Change Color?

Basil leaves will change color for many reasons, but the most common shared reason is that there is something wrong with the nutrients that the plant is getting (or lack thereof). It can also be an indication of fungus, worms, or another form of disease within the plant.

In order to tell the difference between too much water and plant disease, you will have to look more closely at the leaves and pay attention to the pattern of color change. This will usually give you the information that you need to determine what is going on with the basil plant and also what you can do to restore the basil plant’s health before it becomes too late to change it.

If the entirety of the leaf is turning yellow, it can either be an indication of the plant’s natural age (think of people’s hair greying as they age) or it can be an indication that there is a deficiency in nutrients.

If the entirety of the leaf is turning brown, this indicates that there is something going on with the amount of water the plant is able to absorb, with it most commonly meaning that you are either over- or under-watering the plant.

If the areas of browning or yellowing on the leaves are dry and almost withered to the touch, it can be an indication of a condition known as sunscald. Sunscald can be thought of as similar to a sunburn on a person and means that the basil plant is either getting too much sunlight or that the sunlight is too intense for the plant to be able to handle.

If the leaves are spotted and streaking either brown or yellow while also dropping or wilting, then this is a good indication that your basil plant has contracted a type of fungal disease and you need to either try to salvage the plant or figure out what caused the fungus to go after your basil plant.

There’s also a chance that your basil plant may not be able to come back to full health from a fungal disease.

If the leaves of the basil plant are a blend of yellow and brown and ranging into black streaks on the leaves, then this is an indication of bacterial leaf spot. As the name suggests, this is a type of bacterial infection that plants can develop and there are treatment methods that you can switch to so that you can preserve your basil plant’s health.

If the yellowing of the leaves is only present between the veins or along the major veins of the leaves, this is commonly an indication that there is a potassium deficiency and that you need to add some potassium to the soil of the basil plant so that it can get back to full health.

In some cases, it can also be the earlier stages of downy mildew before it progresses into greyish, powdery growths on the basil leaves.

And finally, if the leaves are yellowing, becoming twisted, and are stunted in growth, this is a sign that your basil plant has a case of nematode worms. These worms will commonly go after plants but they can also go after humans, so if your basil plant is affected by them, you should do what you can to try and get rid of them for the sake of both your health and the basil plant’s.

How Can You Restore Your Basil Plant?

Now that you are aware of what yellowing and browning of the leaves can indicate in basil plants, you will want to do what you can to restore your basil plant’s health back to its best.

In some cases, especially with basil plants, readjusting how you water the plant is going to be the best solution, as the most common reason for basil leaves to change color is improper watering (both too much and too little).

On average, basil plants need about one and a half inches of water each week to keep them healthy, and watering them from above or with the use of sprinklers can increase the chances of discolored leaves.

Optimally, you will want to water around the base of the plant and opt to water the plant in either the late evening or early morning, when the sun cannot “burn” the leaves that have water droplets on them.

Adjusting your watering habits to better reflect this has a good chance of helping to restore your basil plant. If your basil is in a pot, you will want to try to check and see if they are rootbound at all, as this can affect how much water the plant is able to absorb even if you are watering it properly.

If you believe that the discoloration of the leaves of your basil plant is due to a nutritional deficiency, you should consider a new fertilizer for it, or add a fertilizer to your planting routine if you haven’t already.

Basil benefits the most from 5-10-10 type fertilizer and requires about three pints of it for every 100 square feet of planting space, in addition to compost, if you want the most from your plant.

If you notice that the nutritional deficiency seems to be surrounding potassium, there are commercial potassium-focused fertilizers that you can add to your basil’s planting area. With these, you will want to follow the instructions on the label of the fertilizer and distribute it to your basil as directed before watering the fertilizer into the rest of the soil.

In a few days’ time, your basil plant should begin absorbing the nutrients and potassium, and if this was the source of the discoloration of its leaves, then you will see this gradually fade away.

If the leaf discoloration persists, you will want to consider looking at some of the diseases and infections that basil can pick up and consider treatment for those, as this may be what is affecting your basil, especially if it didn’t have enough nutrients in the first place to fight off an infection.

With diseases and infections, the best thing that you can do is cut away the infected leaves so that it cannot spread further to the rest of the plant. More often than not, there isn’t a specific cure for these diseases the way that there are antibiotics and medications for people, and your goal should be on preventing the spread of the disease to the whole plant.

For fungal diseases, you will want to follow the same process of cutting away infected areas of the plant so that it cannot spread further. Diseased plant remains should be disposed of in a covered container so the spores will not continue to linger and spread.

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