Why Is Your Purple Basil Changing Color? (And What To Do About It)

Purple basil is a lovely plant that is as edible as it is pretty. This annual herbaceous is also called Purple Ruffles basil as its leaves tend to be clustered as ruffles with the purple basil changing color at times. The changing color of the purple basil can be an issue for some gardeners as they want the true purple color to accent their flower beds.

There are ways around this problem, once you understand the root causes. This plant is widely used as an ornamental addition as it has small purple flowers that produce a striking fragrance. Leaves on the purple basil are usually mostly dark purple, but they can also be a green-purple tone with purple stems.

Some plants change color altogether.

History of Purple Basil

Basil, in general, has always been revered by those along the Mediterrenean. Ancient Greeks called it the “king of herbs” as it is easy to grow and can be used for a variety of uses from scent to food.

Basil can be grown in a yard or in containers, but the climate temperature must be mild either way. The plants are used to warmer climates and so must be protected from harsh, winter weather.

Purple basil is naturally occurring in these warmer regions, but there are also some varieties that were scientifically modified in the 1950s. This is where the hybrid purple basil becomes more popular as it contains both the green and purple hues.

Purple basil has become popular with culinarians because its color adds dimension to salads and vegetables. Its flavor adds a different tone to cooked dishes as it has an intense, almost spicy, flavor over traditional green basil. Purple basil has distinguished itself as among the top herbs for high-end gourmet dishes featured in many restaurants.

General maintenance is to water regularly, use fertilizer two to four times a year and pruning. Purple basil should be pruned once a year. You would also need to prune the stems where there were blooms to keep the plant blooming in the future.

Reasons for Purple Basil Changing Color

Purple basil, like any of the basil varieties, can be tricky to grow and that can become even more difficult when it starts to change color. There could be some issues with the soil, watering, or even a fungus that is causing the problem.

Purple basil is a distinctive variety from the traditional green basil, so this plant is genetically purple even though it tastes similar to the green variety with an additional clove, slightly stronger flavor.

The element that gives purple basil its rich, dark color is a pigment called anthocyanin. Problems with this pigment are often the root cause of purple basil changing color.

Some have noticed that green basil sometimes starts to turn purple, which means it is sick. Typically this means there isn’t enough phosphorus in the soil. However, with purple basil, it will turn green or other colors when there is something wrong with the soil, sunlight, water, or a host of other issues.

The Best Home For Purple Basil

This plant grows best in tropic, Mediterranean, subtropical, or mild climates. It can be grown indoors as long as you monitor the container, soil, water, and any fertilizer used. Common mistakes gardeners make are overwatering, underwatering, or improper sunlight.

Purple basil loves soil that is turned up to six and seven inches deep and that has drainage and a good natural fertilizer base, such as compost.

Why Is Your Purple Basil Turning Green?

Purple basil turns green when the pigment anthocyanin is not functioning properly or it could be the plant is a hybrid plant that mixes purple and green colors naturally. Fading pigment typically indicates a lack of light.

The three potential problems for purple basil turning green are:

  • The pigment is too low
  • Pigment inheritance
  • It’s a hybrid plant,

The most common reason for turning green is a lack of sunlight affecting the anthocyanin. This is the same pigment in other types of basil plants as well as purple cabbage, blood oranges, and cherries. It is what turns plants or their fruit blue or red and this pigment is produced by the plant.

If the anthocyanin is low, the chlorophyll will take over. Chlorophyll is the substance found in all plants allowing them to absorb sunlight and responsible for them being green.

Scientists state a plant under stress will produce more anthocyanin and sunlight is one of those things that produce this type of positive stress. This is particularly critical for purple basil as scientists say it thrives off this kind of stress that comes from a drier, harsher climate.

It is common for purple basil to began to turn green during the winter months because of lower amounts of sunlight. You may want to move the plant to be in more direct, warming rays indoors or invest in an artificial light source to keep the purple hues strong all winter.

Pigment inheritance refers to how young plants look as they grow. With purple basil, seedlings or young leaves may be green when they first start growing. Some may have a mix of green and purple leaves. This is because the plant has an unstable amount of purple pigment.

Gardeners should know that a Purdue University study suggests there is 34 percent of seeds sold as purple seeds are green basil due to the instability of the pigment.

The third option is that you have a hybrid plant. These are common among basil lovers as well as in other similar mixed color plants such as anise, licorice, purple bush, and tulsi.

How to Stop Purple Basil Turning Green?

Those who has plants falling into the first category of a lack of sunlight can easily fix the problem. You will need to up the amount of sunlight. While the minimum for purple basil is six hours of direct sunlight a day, you may need to increase that to get your purple basil to be a truly dark purple.

You may need to change the location of your plant to be more directly in the sun. Finally, buying an artificial light to offer longer rays could be the answer.

Studies from Stefan Cel, Mare University show that an artificial light that has a blue-red combination in an 80-20 ratio doubled the concentration of the pigment in basil when it was compared to ordinary white light.

Some great lighting choices are LED lamps and high-pressure sodium (HPS) lights.

Why Is Your Purple Basil Turning Yellow?

A yellow basil plant is a sick plant and the main culprits are improper waters, fungal disease, and bad growing conditions. Fortunately, all three can be corrected without a lot of difficulty

Improper Watering

Many people over water their plants and this can cause root rot in purple basil. That leads to yellow leaves. Remember, basil is a tropical plant so it loves sunny, drier weather and doesn’t need tons of water.

How to Stop Your Purple Basil Turning Yellow?

Basil gardeners should only water plants when the top two inches of the soil are dry. No one wants soggy soil so the basic rule for basil is to water once a week to 10 days apart when the plant is fully grown.

Another key point is to make sure any container pots you use have at least one drainage hole. This is a common mistake because many novice gardeners buy decorative pots that look great but fail to drain properly. Drainage is critical with any plant but is especially important when it comes to all varieties of basil.

Fungus

The most common fungal disease that affects purple basil is downy mildew. This fungus quickly spreads. You will recognize it when the basil leaves turn yellow and then develop a fuzzy, gray, or brown growth.

Catching the problem early is paramount to saving the plant. You can stop the disease by clipping the affected area off in hopes of saving the rest. Those plants that are too far gone should be disposed of in a way they don’t affect the rest of your garden or flower bed.

Another fungal disease that is common among purple basil is fusarium wilt. The cause of fusarium wilt is a fungus in the soil that assaults purple basil inside the stem tissue that is responsible for moving water throughout the plant.

Most basil plants, including purple basil, mature when they reach six to 12 inches tall. You won’t see the disease appear until after they mature. Fusarium wilt causes brown spotting and streaking on the stems. It also causes the leaves to wilt, turn yellow and drop.

One of the first signs of this disease is a little yellowing along the leave’s major plant veins. Then, brown spots show up within the yellow spots and began to spread over the entire leaf. After that, leaves display a powdery, gray growth underneath the infected yellow spots.

It progresses quickly until the leaves drop off and the plant dies.

While fungicides may be a good option for other plants, they aren’t the best choice to treat these kinds of diseases on basil. The Clemson Cooperative Extension office advises to keep the leaves dry and improve airflow around the plants.

Circulating air helps control both downy mildew and fusarium wilt. For this to be successful, there must be enough space around the plants to allow for ventilation. The idea is to reduce leave moisture, so whatever you can do to improve that will help our plant.

Bad Environment

Another common issue stemming from yellow leaves is inadequate growing conditions. Purple basil likes milder to warm temperatures. It’s best if daytime temperatures are above 70 degrees with nighttime temperatures above 60 degrees.

Those who plant these plants too early or fail to bring them in during the winter could see yellow leaves. A lack of sunlight is another issue causing yellow leaves, just as it is with purple basil turning green.

Yellow leaves could mean there isn’t enough sun to bring out the darker color. One thing to note about purple basil is that older leaves turn yellow eventually, but that shouldn’t happen for a long time. Leaves located near the bottom of the plant near the dirt will also naturally turn yellow because those don’t get the sunlight of those leaves on top of the plant.

Why Is Your Purple Basil Losing Color?

Purple basil can also lose color or turn white. This can happen to the green varieties too. This is most likely because of root rot. Root rot can be corrected if caught early. You will first notice root rot when the leaves on your purple basil droop. They will turn another color, like white, yellow, or maybe even brown or black.

Another problem that leads to a loss of color, as well as yellow leaves, is a lack of fertilizer in the soil. You should add compost before planting, but that can diminish over time. Purple basil can suffer from a potassium deficiency where they develop yellow spots between the leaf veins.

Most plant experts state gardeners need to apply fertilizer applications on the sides of the plant about once every two weeks. The standard is to use around one-third cup of fertilizer for around 25-square-feet of space.

Be sure to scatter the fertilizer and lightly water the plants afterward to make sure the nutrients seep into the soil. Regarding fertilizer, purple basil loves soil full of organic matter and rich nutrients so be sure to use a natural element fertilizer like compost. This is the best option to ensure your plants have optimum growth and color.

How to Stop Your Purple Basil Losing Color?

The solution is pretty simple. Spread out the watering times to allow more time in between. Also, try your best not to water the leaves but aim at the roots.

Another more dramatic solution is to change out your pot and soil. Typically, soggy soil takes time to dry out and your plant may not have that kind of time. It could also be the pot doesn’t have proper drainage.

Re-potting your plant in a container with drainage and fresh, drier soil could save it. If you are going to re-pot, you should go ahead and make sure the soil is high in nutrients. You can create more potassium in the soil by using a commercial potassium fertilizer, like muriate of potash. Be sure to follow instructions for its use.

What Can You Do to Keep It Purple?

The answer is sunlight, sunlight, and more sunlight. That is the key thing in maintaining the color of your purple basil. Keep the fertilized soil on the drier side and make sure it’s in a temperate environment.

Overall Maintenance of Purple Basil

Purple basil can be low maintenance if you do some basic things upfront such as picking the proper garden spot and planting it at the right time of the year with warmer temperatures. Placing your purple basil in the right area at the beginning of growth will prevent many problems later.

One thing that is crucial to this plant is sunshine. These types of plants should receive full sunlight for at least a minimum of six hours a day. The best places for this amount of sunshine are either on the east or west-facing sides of your property.

Temperatures need to be above 60 degrees at night when you plant purple basil. It is crucial when planting it outside that it goes in the ground after the last frost date in your area. It should be planted shallowly just one-eighth inch deep in well-turned soil with some good compost.

Water twice a day until seeds are growing, then taper off to once every few days. You may need to thin the row out to allow for 12 inches between plants.

Other Issues You May Have with Purple Basil

  • Purple basil can have other problems that will need to be remedied including:
  • Leaves turning dry and brown from sunscald
  • Yellow to brown or black streaking on stems from bacterial leaf spot yellow
  • Stunted, or twisted leaves from Nematode worms

All of these problems can be remedied with proper care, watering, and pesticides. There are some special care you need to take when it comes to diseases like bacterial leaf spot and fungal diseases.

Bacteria leaf spot causes yellow to brown and black streaking on water-soaked stems along with spotting on leaves. This happens when the soil is infected by the Pseudomonas cichorii fungi. The soil ends up splashing on the plants when it rains or they are watered.

This disease is a big problem in warm and humid weather and there is no cure for it. The best option is to cut off infected leaves as soon as they show up. Also, wipe your shears or scissors clean with an alcohol-soaked cloth to prevent the disease from spreading.

Another way to prevent this disease is to water the purple basil at the plant base to avoid soil from splashing onto the plants.

Strawberry leaf nematodes are attracted to basil plants, including the purple variety. Nematodes are tiny worms that eat the basil leaves, causing them to turn yellow and become twisted and stunted. The holes eaten by the worms turn brown before dropping from the rest of the leaf.

These worms require one thing to complete their mission. They need standing water on the leaves. This is another reason gardeners need to be careful when they water as dry leaves are a good preventive.

There isn’t a way to control these pests with a chemical because such chemicals are only available to professional growers. Home gardeners must remove any affected plants to keep the worms from spreading.

Recap

While purple basil is easy to grow, those who try their hand at it need to be careful when it comes to the following:

  • The environmental temperature
  • Moisture around the plant
  • Sunshine
  • Compost

Basil enjoys warmer climates and planting it in colder areas where temperatures routinely dip below 60 degrees will cause the plant to suffer and its leaves will turn yellow, brown, or black. The planting season is after your region’s first frost and you should bring your plants in before the first fall frost to help them grow during the winter.

Young purple basil plants thrive from heavier watering with most experts recommend watering seeds twice a day. However, water should be reduced as the plants grown and should be limited to one every seven to 10 days once a plant reaches maturity of 6 to 12-inches tall.

This will help prevent leaves from turning yellow or white as over watering leads to root rot. A lack of sunshine is detrimental to purple basil plants asreducingd sun will also diminish the element in the plant that makes it purple.

Reduced sun allows chlorophyll to grow, which will make the leaves turn green instead of their intense purple color. Those who have the healthiest purple basil plants will put them in direct sunlight for at least six hours a day and on up to 10 hours a day for maximum benefit to the plant.

Compost is another important element for purple basil. This is a plant that needs a nutrient-rich soil to do well and maintain the distinctive purple color. natural-based compost mixed into the soil works the best. It doesn’t need fertilizer to regularly, but you will need to add more fertilizer around the sides of the soil a minimum of a couple of times a year. 

Conclusion

Purple basil offers a unique plant for visual interest in a garden as well as providing a deep, rich flavor to food. It can be a fairly easy plant to grow with some basic knowledge and guidelines.

 Although the purple basil can have its share of plant health issues, most are easily remedied and well worth the effort. This plant can add beauty, fragrance, and taste to your home for years with proper care.

Sources

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