Why is basil turning yellow?

Just Veggies

It’s a rite of spring: I plant basil transplants into the garden in May and they turn yellow. I fret. And after a few weeks of fretting the basil is suddenly joyously green. I am then free to fret about some other crop, typically my beets or chard.

My basil turns yellow pretty much every spring, and I bet maybe yours is becoming or has become yellowish, too. Here are a few possible reasons why.

Too cool, or too cold

Basil originates from India and eastern Asia, so it’s understandable that it prefers warm temperatures. And remember, if you buy basil in a pot from a garden center, it’s likely been treated in a warm and cozy greenhouse. The shock of being outside in temps under 50F can be too much for the plant.

Too wet

Basil doesn’t like to be too wet. And it’s been raining a lot here. Basil likes well-drained soils. In fact, it likes horrible soils and I’ve grown it in some rotten places with much success. But too much water makes basil unhappy.

Prolonged wet weather also can cause the growth and proliferation of a certain type of downy mildew. See the brownish spots on those leaves? Could quite possibly be an indication of “fuzzy brown stuff” under the leaves. I haven’t gone back to the garden to verify, however. Afraid to look, actually.

Lack of nutrients

Basil may like horrible soil, but it does need some nutrients in order to grow. Yellowing leaves can often mean the basil needs some sort of nutrient application, like a balanced fertilizer (10-10-10). All the rain may also mean the nutrients are being washed away or rinsed downward and out of reach of the basil’s roots.

Not enough sun

Basil prefers full sun conditions, and its vibrant green will begin to fade when it doesn’t receive enough light.

In my case, I’m pretty sure I plant the basil in the garden too early each spring. I should know by now to wait until the first of June. This year, I probably should have waited longer.

Is your basil dying? Turing yellow and brown? Join the crowd. Last year was the first year that my sweet basil didn’t flourish. Sadly, they turned yellow, then brown and subsequently died. I learned during my master gardener classes that my basil dying was caused by downy mildew. So if you want basil this year, learn the facts and how to keep downy mildew at bay in your garden.

Why are Basil Dying?

This pathogen, Peronospora belbahrii, which causes downy mildew is deadlier than the Terminator. It wipes out your sweet basil (Ocimum basilicum) patch in the blink of an eye.

All of your sweet basil.

In fact, if you live in Florida or Texas, like the Terminator, this pathogen says, “I’ll be back” since it is a year round problem.

Thank goodness for New Jersey harsh winters since it wipes out the pathogen. But it will be back too.

Where Did this Pathogen Come From?

According to Cornell University, the original outbreak occurred in Uganda in 1933. It was observed again in Switzerland in 2001, Italy in 2003, France and Belgium in 2004, and subsequently spread to Israel, New Zealand, Canada, the United States, Iran, and several African countries.

In the United States, the pathogen has spread to basil plants in North Carolina, Pennsylvania, New Jersey, Minnesota, Massachusetts, Kansas, and Florida. Cornell speculates that the pathogen may be in other areas of the United States; however, growers may think that the basil died from other causes.

Twenty percent of basil is imported to the United States. Leaves could contain the pathogen. Between contaminated seeds and plants, the pathogen took hold around the world.

How Do You Know if You have Downy Mildew?

According to the University of Minnesota,

  • The infection starts at the lower leaves and moves up the plant;
  • At first, the plants turn yellow which could be interpreted as a nutrient deficiency.
  • Then, irregular black spots appear.
  • In addition, fluffy gray spores grow on the underside of the leaf.

Eventually the effected leaves turn brown and the plant dies.

The pathogen spreads via contaminated seeds and wind dispersed spores. Once one plant gets sick, the others follow suit.

High humidity and/or dampness like wet springs make this pathogen one happy fella.

The weather conditions of the east coast are prime for the spread of this pathogen. In New Jersey, we generally have wet springs and very humid summers.

The Research to Come Up with a Fix:

Unfortunately, there aren’t any sweet basil varieties that are not susceptible to downy mildew.

Since 2011, a team of researchers from Rutgers University , University of Massachusetts, Cornell University and University of Florida have assembled to develop a strategy on managing downy mildew in basil.

(If you are interested in getting more detailed information as to what has been discovered by the team, watch for the videos from the 2016 Basil Downy Mildew Workshop Sessions.)

In addition, the Rutgers team is in charge of developing new sweet basil varieties that are resistant to downy mildew. The team has one of the largest basil breeding grounds in the United States.

Is All Basil Susceptible?

Not all types of basil are as susceptible as sweet basil. Less susceptible varieties include:

Moderately susceptible:

  • Red Rubin and Red Leaf (O. basilicum purpurescens)
  • Thai Basil
  • Lemon Std., Mrs. Burns Lemon, and Lime,

Least Susceptible:

  • Blue Spice, Cinnamon, Spice & Blue F1

Interestingly, Eleonora is the first sweet basil to be moderately resistant; however, its level of resistance is not sufficient without using fungicides. It can be purchased HERE or HERE.

Tips to Grow Sweet Basil:

If you insist on planting sweet basil, here are some tips to keep the pathogen at bay:

  • Plant as soon as you can and realize you might only get a spring harvest.
  • Make sure that your basil is planted in full sunlight.
  • Space your plants to allow for good air circulation.
  • Use drip irrigation so the leaves don’t get wet.
  • In a greenhouse, keep the lights on at night since this pathogen needs 7 hours of darkness to create spores.
  • In addition, in a greenhouse, keep the humidity below 85% in the canopy of the plants if possible.
  • Buy pathogen free seed. (Meaning don’t get seeds from your neighbor’s last year plants.)

What About Fungicides?

Commercial growers can use fungicides as a preventative. Learn about them HERE and HERE. Unfortunately, organic control for homeowners are insufficient to control the disease.

According to the University of North Carolina,

“Products containing the active ingredients copper or chlorothalonil (the trade name of one product with chlorothalonil is known as ‘Daconil’) are the best and only effective products available to home gardeners. In addition, home gardeners should grow varieties with tolerance if they are worried about basil downy mildew in future years because most chemicals available to the home gardener are not sufficient to control basil downy mildew once it appears.”

Other non-organic approved fungicides reduced the disease by 70-90%.

Once a plant is inflected, get rid of it. Don’t compost it.

Who Wants Dying Basil. What’s My Options?

I felt the same way. Either harvest early or plant the other varieties of basil listed above until Rutgers creates a hybrid that is resistant to this pathogen.

Join the Conversation

Did your basil die last year from downy mildew?

Photos by Scot Nelson here, here, and here.

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Why Is My Basil Plant Turning Yellow?

Basil can turn yellow after it has fully matured or as a result of improper growing conditions. Typically, basil begins to naturally yellow after the plant has produced seeds.

Cool temperatures may cause the basil plant to begin yellowing. The plant should be moved away from windows at night if the temperature is at or below 32 degrees Fahrenheit. Basil that’s grown outdoors should be planted in a sunny location and protected from frost. Too much or too little water may cause basil plants to yellow. Water when the top layer of soil feels dry, and plant the basil in a container that has drainage holes.

If the basil has yellow leaves near the bottom of the plant, the plant may require additional nutrients. Add nitrogen-rich, liquid fertilizer to the plant’s water until the leaves have returned to their normal color. Then fertilize with potassium-rich fertilizer at least once per week.

Basil that has recently been transplanted into the garden may yellow as a result of the environmental change. Before transplanting herbs to the garden, harden off the seedlings by exposing them to the outdoors in increasing increments of time over the course of a week. To harden off seedlings, take them outdoors for one hour the first day, and then increase the amount of time spent outdoors by one hour each day. After the seventh day, the seedlings are hardy enough to survive outdoors.

If your basil plant is dying and you don’t know why, don’t panic or beat yourself up. It’s a common experience that almost all herb gardeners pass through.

Although basil is a plant that can grow anywhere, especially at home, it can be a bit sensitive towards unfavorable growing conditions and can suddenly break down under stress.

Nonetheless, this herb is good at showing signs of discomfort.

Basil doesn’t leave things until the last moment, and it asks for help quickly when stressed. Perhaps you’ve already noticed from your plant’s appearance right now.

The distress your basil is passing through can be triggered by several causes that I’m going to discuss thoroughly in this article.

Don’t worry; you will be able to save your basil (if it isn’t too late). Moreover, you will be much more prepared to grow and care for basil properly.

Why is Your Basil Plant Dying?


The number one cause of stress and death in basil plants is overwatering. It’s the most common and the most innocent mistake beginners make.

Watering basil can be a very delicate activity, especially when we’re talking about indoor gardening.

Outdoors, water evaporates faster, which prevents it from accumulating in the soil for long periods. This keeps potted outdoor basil plants thirstier than indoor ones.

People who are taking their first shot at growing herbs indoors underestimate the importance of moderate watering, and they will water their basil plant each day, or every other day.

That could be problematic, especially when we’re talking about an environment in which the temperature is balanced and not high enough to pull the trapped water out of the pot.

  • Symptoms:

Overwatered basil will show signs of wilting. You might also observe leaves turning yellow or dark brown, and this could be dangerous.

If you suspect you’re overwatering your basil, the first thing to do is inspect the roots of your plant.

You will know it’s too late to save your basil if a huge part of its root is brown and softened, which means it has rotted.

  • What should you do?

If the damage to the root is minimal, you can still save your basil by transferring it to a new pot containing dry, well-draining potting soil.

Remember to only water your potted basil daily when you’re growing it outdoors, on a balcony for example, and the days are getting hot.

Indoors, plan your watering schedule according to how fast the potting soil dries.

Don’t be afraid to use your fingers to feel the soil every day. When it develops a dry touch, it means it’s time to water your basil.


It’s very important not to leave the soil until it dries too much, or else you would be underwatering your basil.

Sometimes, people neglect their potted basil for days and water it only when they “feel” like it or when they remember to.

That can be slightly tolerated when the pot isn’t losing a lot of water during the day, but if the plant is growing on a windowsill or in a hot room, underwatering can be fatal.

  • Symptoms:

Underwatered basil plants also show signs of wilting. In most cases, their leaves turn yellow (usually starting from the bottom) and they appear to be shrinking considerably.

  • What should you do?

Basil plants that have been underwatered can be saved by immediate watering if the cells are minimally damaged.

Sometimes, it’s impossible to save your basil when its system has been highly impaired due to the lack of water.

This happens when the plant has been neglected for several days.

A proper watering schedule is the only way to prevent underwatered basil. Don’t skip watering days, and don’t wait for the soil to get too dry.

Also, remember to increase the times you water your basil when temperatures around your plant get hotter.

Too Little Light

Basil grows in partial or full sun, which means it needs at least 4 hours of direct sunlight every day.

Some gardeners who grow their herbs at home can’t find a sunny location inside that can provide that amount of light, and the result is a plant that can’t synthesize its own food and is trying helplessly to find the light.

  • Symptoms:

Basil plants that are not getting the amount of light they need have long stems and a reduced number of leaves that are sometimes discolored (usually yellow).

  • What should you do?

Saving your basil in this case also depends on how fast you are. You need to provide your plant with heavy amounts of light.

You can either search for a sunny location inside or simply purchase grow lights that can complete your basil’s quest for light.

Grow lights are widely available in the market and most are optimized to provide little amounts of heat that might harm the plant.

Nutrient Deficiency

Nutrient deficiency is often overlooked by many gardeners. Malnutrition in basil is serious and can happen frequently.

Basil is a fast-growing plant, so it’s obvious that it needs a lot of nutrients to support its rapid growth.

When the soil isn’t rich with food, basil declares an emergency situation and reduces its growth.

If basil goes without enough food for a prolonged period of time, it will eventually pass away.

  • Symptoms:

Malnourished basil has yellow or discolored leaves and very slow growth. If your basil is getting enough water and light, but it’s still growing slowly, it’s probably malnutrition.

  • What should you do?

Nutrient deficiency can be treated by adding fertilizers to the soil. You can use compost, vermicompost, shellfish, or any other soil amendment to enrich the soil with nitrogen and essential minerals.

Also, remember to repot your basil every few months. As you know, when the soil is left in the pot for a long time, it becomes devoid of nutrients.


As basil grows tall and spreads its branches all over the place, it also becomes huge below the soil. Its root system expands to aid its overall development.

When your basil is potted, its roots can keep on growing until they bump into the walls of the container. At that point, your plant becomes crippled.

Being trapped and unfree to expand, the roots will go around in circles and suffocate themselves. Basil will stop growing, and eventually, it will die.

  • Symptoms:

Yellow leaves, leggy branches, and stunted growth are all signs of rootbound basil.

Nonetheless, the most distinctive feature of this issue is what happens to the roots. They stop growing in a straight manner, and instead they will have a circular shape.

You can suspect that your basil is rootbound If the container it’s growing in is too small in comparison to its size.

  • What should you do?

To free your basil, start by taking your basil out of the pot. Afterward, cut all the roots that have the shape of the pot they were in (usually, these are circular).

Once you prune the abnormal roots, loosen the other roots so they hang down, loose and free.

Bring in a new, wider and deeper, pot and transfer your basil to it.

Water the plant heavily and avoid exposing it to too much light for the first few days.

Changes in Temperature

Basil is sensitive to abnormal temperature fluctuations, particularly when it’s being exposed to cold weather in the process.

During such an extreme variation in temperature, you can simply lose your herb for good.

  • Symptoms:

Black and deformed leaves are the greatest indication of cold temperature intolerance in basil. In addition to that, the plant growth will be stunted.

When it’s too hot, the plant will simply wilt and its leaves will turn yellow.

  • What should you do?

Learn all about basil’s temperature tolerance here to discover the optimal temperature for your basil plant.

Excessive Transplanting

Basil doesn’t like changing pots too much. Changing pots excessively can shock your herb’s stability, which may lead to death.

  • Symptoms

Stunted growth and wilting are the main symptoms of a basil plant that has been replanted too many times.

  • What should you do?

Don’t put too much stress on a newly transplanted basil. Avoid watering the plant excessively or exposing it to direct sunlight for long periods of time.

It might take a few days for the plant to adapt to its “new” environment.

Fusarium Wilt:

Fusarium wilt is one of the most common fatal diseases that affect basil. It’s a relatively new disease, and it affects sweet basil the most.

The wilt is caused by some species of fungi that can invade the water-transporting channels in the stem of your plant.

  • Symptoms:

Wilting and crumbling of the leaves, darkening of some parts of the stem, asymmetrical growth, and root rot are all signs of the disease.

  • What should you do?

Unfortunately, there’s still no cure for fusarium wilt.

The only way to deal with this issue is to get rid of the infected plants immediately so as not to infect the surrounding plants.

Pay attention to where you buy your soil, seeds, and plants from and always purchase high-quality products. This is the best way to prevent the disease.


Flowering and seeding are the last stages of your basil’s life cycle. At the end of this stage, death is inevitable.

  • Symptoms:

The main symptom here is the development of flowering buds, then seeds, followed by yellowing of the leaves.

  • What should you do?

If It isn’t too late, you need to pinch off the flowering buds at the top of each branch. This activity is called dead-heading.

Dead-heading your basil isn’t just important for its health but also for its flavor.

Supermarket Basil

In all honesty, buying your basil from the supermarket isn’t the best idea ever.

Plants that grow in the supermarket are usually very weak and sensitive.

That has to do with the fact that the environment inside the store doesn’t teach the plant how to adapt to and resist harsh conditions.

  • Symptoms:

Many supermarket basil plants will start wilting for “no apparent” reason. Their leaves will fall down, their stems will eventually turn brown, and the plant will die.

  • What should you do?

Supermarket basil plants aren’t hardy enough. To harden off your basil, you need to expose it to harsh conditions gradually.

Place the plant for a few hours on a balcony each day, but most importantly, let it in at night.

This will push the plant to develop a more protective mechanism that will strengthen it.

Hopefully, with all this information, you will able to save your basil if you notice some unhealthy characteristics. If it’s late, however, don’t worry; you’re much more prepared now to grow basil successfully next time.

Don’t forget to share your questions and thoughts in the comments below!

Now that my basil is growing, what should I do about yellow leaves? | The Kansas City Star

Late-growing basil plant Submitted


I started my basil plants late this year, on May 10. They didn’t grow much at all for the first four weeks, and then started to yellow and develop brown patches. But once the constant rain finally moved out, I’m starting to see what looks like healthy new growth on top. Where should I go from here? Should I remove the yellow leaves at the bottom, or leave them be? – Derek


Yellow leaves on basil could be a number of things, so here are a few things to consider.

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Since you planted the basil in May, the weather has been generally cool, cloudy and very wet. The older leaves could be responding to the sudden change in temperature and very hot sun, resulting in sunscald. In this case the plant will grow out of the condition. Just cut off the yellow bottom leaves as they die.

And how is the drainage? Basil needs good drainage.

Next, have you fertilized the plants? With all the rain we have had, they could be deficient in nitrogen. Nitrogen is mobile in the soil and will wash out. Also, too wet conditions can tie up nutrients in the soil that the plants need. Try an application of a balanced fertilizer.

Lastly, check the underside of the yellowing leaves. Are there any spots, fluffy grayish spores, webbing? If so, post again, with a picture of the underside of the leaves.

Hope this helps.

Carole-Johnson County Extension Master Gardener

Basil Sunburn

There’s an important step between growing a seeding in the house and moving it to the garden. Before planting seedlings outside, they need to be hardened off.

Hardening off is the process of acclimatizing a plant to a new growing condition. When you start plants inside and grow them in either a sunny window or under lights, the plant is growing under very stable and controlled conditions. The light isn’t as strong as the sun; the water is constant; there is little or no physical movement of the plant like that caused by the wind. When you add all of these factors together, you end up with a plant that isn’t tough enough to face life outside of the house – they’re literally “hothouse flowers,” weak and easily damaged. The tissues of the plant are soft and the protective layer of waxy cuticle on the leaves is very thin.

In order to make the transition from inside to outside, the plants needs some time to adjust or “harden off.” This is done by slowly introducing the plant to the conditions it’ll face in the garden. It’s often suggested that you place the plant in the morning sun for one hour on day one, then two hours the next day, etc. While this process makes sense, it’s far too structured for my taste. Instead, I put my tray of plants on an open porch where they only get a few hours of morning sun. Here they’re exposed to sunlight and have some physical movement caused by the wind. After about a week the plants are more sturdy and I feel safe to plant them in the garden.

Basil with Sunburn

As I was checking a pot of herbs, I realized the my basil plants weren’t full hardened off before I planting them. While the plants are growing fine, there are some leaves that are chlorotic (yellow) with a little bit of burning. What happened is that the intensity of the sun has scorched the leaves. It’s often called sunburn but it’s a very different process from the sunburn that we might get on a sunny day.

For a plant, sunburn occurs when there’s too much sun and too little water. The basil plants in my herb pot hadn’t had enough time to develop a full protective cuticle layer so too much of the sun’s energy was getting into the tissue of the leaf. As newly transplanted seedlings, the roots of the plants weren’t very developed so the absorption of water was a little slower than it would be in an established plant. The result of too much sun and too little water is that the leaf tissue dried out and died.

In this case it’s hardly a problem – the only damage was a few burnt leaves. But I’ve had plants die from not being hardened off properly. It’s tempting to want to take a plant that’s been growing inside and put it directly into the garden, but the results can be disastrous! In the case of seedlings grown in the house, a little bit of time spent hardening off a plant is worth the effort.

Information On How To Grow Basil Indoors

While basil is a commonly grown herb outdoors, this easy-care plant can also be grown indoors. In fact, you can grow basil inside much the same as you would in the garden. This wonderfully fragrant herb can be grown for use in the kitchen, making aromatic oils, or simply for aesthetic purposes. Let’s look at how to grow basil indoors.

Basil Growing Indoors

Growing basil indoors is easy. Container grown basil should be planted in well-drained, nutrient-rich soil. Using the proper soil type is important in order to successfully grow basil inside. As basil is not tolerant of water stress, make sure pots provide adequate drainage. While the soil should be kept somewhat moist, it should never be soggy; otherwise, the roots will be prone to rotting.

Basil growing indoors will require fertilizing. Depending on the variety grown and its overall purpose, a general houseplant fertilizer can be used. As with many houseplant fertilizers, this should be used at half the recommended strength. However, basil used solely for flavoring foods requires the use of an organic fertilizer. Organic fertilizer also helps to maintain pH levels when growing basil indoors.

Healthy pH levels are another important aspect of quality soil. You should check the pH levels of soil about once a month or every four to six weeks for optimal growth. Sufficient pH levels are usually between 6.0 and 7.5.

Best Lighting to Grow Basil Inside

Additionally, when growing basil indoors, lighting is important. Basil growing indoors requires at least six hours of sunlight. Basil plants should be placed in a sunny window, preferably facing south. Otherwise, these potted plants may need to be grown under fluorescent lights. With this type of lighting, basil plants will need about 10 hours of light for healthy growth. However, basil grown indoors can also be given both sun and artificial lighting by alternating so many hours in each.

While growing basil indoors is an easy endeavor, the vigorous growth of plants may require frequent repotting.

If you follow these few easy tips on how to grow basil indoors, you will be rewarded with this delicious herb year round.

Brown spots on basil may mean sunburn

Carol Savonen Special to the Statesman Journal Published 10:41 AM EDT Jul 17, 2017 Keep basil such as this Siam Queen healthy by being on the lookout for too much sun, especially after planting, which can cause sunburn. Statesman Journal file

Question: I purchased six basil plants (2 per pot) about a month ago, which I repotted into larger containers. I put them out on my sunny back deck. About 2 weeks ago, I noticed that on all of the plants, there were areas of browning to the leaves on one side. Any idea what is causing this and what to do about it? I’d like to make some decent pesto out of these little guys.

Answer: Your purchased basil plants may have suffered from sunburn. Yellowing or browning, particularly on the south side of the plant is a common symptom of sunburn in plants. The long sunny days and hot temperatures of summer can lead to sunburn on some plants. The starts you purchased were most likely stored in the shade at the nursery or market where you bought them.

Or, on the other hand, if your basil plants experienced temperatures lower than 40 degrees, their tissue could have be cold-injured. Basil is a tropical plant and cannot tolerate colder temperatures.

The next time you buy starts, acclimatize them to the conditions over a period of days. The first day after you transplant them, move the pot into the sun only for an hour or so. Then bring it back into a partly shady area. The next day, leave them in the sun longer. Or, get some shade cloth, and put it over the plants during the sun’s hottest hours. And, if cold nights are forecast, move the pots to a warmer, protected spot for those evenings.

Many other kinds of plants are subject to sunburn. Rhododendrons and hostas are commonly chronically sunburned when they are mistakenly planted in full sun. Some varieties are better adapted to sun than others. Check at the time of purchase for sun tolerance. Others prefer a partially shaded site.

Newly planted plants or young plants with underdeveloped root systems are particularly susceptible to sunburn. Young plants are growing really fast and require a lot of water. Their root systems are still developing and sometimes are not caught up to the size of the above-ground portion of the plant. To add insult to injury, summer days are really long, so plants might have to put up with sunlight for 12 hours or more.

Berries also can show signs of sunburn, especially the red raspberry and blackberry. Sunburned raspberries have white “drupelets,” on the sun-exposed side of the berry. Drupelets are those tiny round sections that make up a raspberry. These colorless drupelets do not otherwise affect the quality of the fruit. You can still eat them.

MORE: Read past gardening Q&As from Carol Savonen.

Dark-colored blackberry fruits absorb heat, especially on the sun-exposed side. When sunburned, droplets of trailing varieties can become red and soft and taste overripe. But they are still edible. Gooseberries can exhibit browning if sunburned. Grapes rarely get sunburned except if leaves are removed late in the season, exposing previously shaded grapes to full sun.

The best way to prevent sunburn is to learn your plants’ requirements for sun or shade before you plant them, then plant them in the right place. If your plants are already in the ground and are getting sunburned, either transplant them to a better site or amend heavy soils with compost so the plant can develop better roots. Make sure your plants are getting enough water and fertilizer for optimal health and minimal stress.

A short-term solution for sunburn is to protect them with shade cloth. I sometimes protected newly potted plants on my deck by moving the potted plants under a picnic table or under a lawn chair, plastic milk crate or on the north side of a larger pot for a few days until their roots get more established.

Carol Savonen is a naturalist and writer. She is an associate professor emeritus at OSU and tends a large garden in the Coast Range Hills west of Philomath with her husband and dogs. She can be reached at [email protected] or c/o: EESC, 422 Kerr Admin. Bldg., OSU, Corvallis, OR 97331.

Published 10:41 AM EDT Jul 17, 2017

How to Troubleshoot Basil Plant Leaves Turning Yellow

basil image by aliengel from Fotolia.com

All varieties of basil are annual plants, meaning that their life cycle can be completed in a single year. If you remove the flowers and buds as soon as they appear, you can get your basil to continue growing and providing delicious leaves longer than expected. Basil leaves produced after the plant has begun to flower usually taste bitter. Yellow leaves on the basil plant are not uncommon and there are several directions to look in when troubleshooting the causes.

Determine how long your basil plant has been growing. Has it already produced flowers, or gone to seed? If so, it is nearing the end of its growth cycle. Basil leaves that are old will turn yellow, indicating no problem other than age.

Examine the watering conditions for your basil. Do not overwater or underwater, as both situations can create yellow, drooping leaves.

Consider the last time you fertilized your basil. Feed it a potassium-rich fertilizer on a regular basis to replace the nutrients it drinks. Feed the basil plant slightly more often if it lives in a pot, as nutrients are washed out of the bottom of the pot every time you water.

Make sure the basil is in a comfortable temperature range. Do not let an indoor basil plant sit too near windows when nighttime temperatures approach freezing.

Consider the possibility of sun scald. Harden your basil off, if you have been growing it indoors, before moving it outside. the difference in ultraviolet light strength can be too much for your basil plant to handle otherwise.

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