5 Reasons Why Is My Cauliflower Turning Purple

The reason your cauliflower is turning purple is because of anthocyanin. It is a water-soluble pigment that appears in purple. The same pigment appears in blue, red, or black in other plants such as blueberry, raspberry, black rice, red cabbage, and many other fruits and vegetables.

This article will explain why cauliflower turns pink or purple and how to avoid this. We will also discuss how this changes cauliflowers taste and quality.

Reasons For Cauliflower Turning Purple

The purple color can start appearing on cauliflower edges, across the top of the curd, or on the stem. It is also possible for the whole head to turn purple. This is caused by a pigment that is present in a lot of fruits, berries, and vegetables called anthocyanin.

Anthocyanin is a water-soluble pigment aggravated by sun exposure and responsible for cauliflower turning purple. The changes in the environment encourage anthocyanin production and cause discoloration. [1]

In shops, we only see snowy or creamy white cauliflowers. So, for most gardening beginners, such a color change can be worrying. 

And of course, at the commercial level, the color change will affect the sale, but a backyard grower should not worry about it. Pink or purple cauliflower is safe to harvest and eat!

There are several reasons why cauliflower might turn purple. These are:

Let us discuss why cauliflower turns purple and how to solve it.

Temperature

Cauliflowers are cool-season vegetables. Their heads must be shaded from the sun to maintain the snowy white color. When it is exposed to heat and sunlight, the level of anthocyanins increases which causes the head to turn purple. 

This usually happens when this vegetable is grown at the wrong time of the year. The color can be affected if it is planted when the temperatures are too hot. If it is planted too late, when it is too cold, the frost might kill the plant.

This vegetable requires a soil temperature between 70 to 85 ^oF (21 – 30 ^oC). If the temperature goes over, your cauliflower will likely turn purple. 

Solution – Choose The Right Time Of The Year To Plant Your Cauliflower!

Take into account the range of temperatures in your area. You do not want to plant your cauliflower when the temperatures are too hot, but also, you don’t want to grow it when it is too cold.

If you grow your cauliflower in the summer months, you might want to consider planting them in the shade or under the cover. You can use windbreak netting that provides UV protection to create shade.

Pro Tip: Use the blanching process. When cauliflower grows, the leaves around the head will become bigger. Blanching is when you tie up the large loose leaves to create shade for the cauliflower head. Just don’t make it into a house for pests!

Soil Nutrients

Cauliflower grows well in well-drained, fertile soil rich in nitrogen and potassium. However, if the plant receives too much nitrogen, it creates premature heads, and the outer leaves are not big enough to protect the curd from sunlight. This causes the cauliflower head to turn purple.

The deficiency of potassium and nitrogen can also be the cause of a purple hue. So, keep your nutrient level just right. 

Solution – Make Sure Your Soil Has Enough Nutrients!

Add compost before sowing seeds or transplanting. It will help to improve the fertility of your soil. This includes manure and homemade or store-bought compost. 

After your plants have grown a bit, add organic vegetable fertilizer to the soil. Follow the directions on the label. Usually, it is recommended to use it every 2 weeks (14 days).

Cauliflower Variety

Most of us only know snowy white or creamy white cauliflowers, but there are many different varieties. They vary in shape, size, texture, and even color. 

Cauliflower variety is one of the factors that can affect cauliflower’s color. Some varieties are more likely to turn purple than others. So, it is essential to understand that it is not always a bad thing. 

Solution – Choose a Suitable Variety!

If you don’t want white curd, choose a purple cauliflower variety. Popular purple-colored cauliflower varieties include:

• Graffiti,
• Violet Queen,
• Purple Cape,
• Rambo purple,
• Sicilian Violet.

White cauliflower varieties (which may change to purple):

• Snowball,
• Snow Spring,
• White Corona,
• Early White,
• Cornish.

Ricing

Cauliflower ricing is the process when the plant goes into the reproduction stage. Curd (cauliflower head) will start to develop flowers. So the whole head will have a velvety appearance with small flower curds known as ricey curds. As the buds form, the head might turn to pink or purple color. 

The most common causes of cauliflower ricing are one or a few from the list below:

• High-temperature fluctuation,
• Too much nitrogen in the soil,
• Too much moisture in the soil.

Solution – To Prevent Ricey Curds, Take These Precautions!

• Plant varieties that are suited to your hardiness zone.
• Do not plant cauliflower during the summer heat. Plant either early or late. This way, you can harvest it before or after the summer heat.
• Maintain good soil drainage to prevent moisture buildup.
• Space out seedlings properly as described on the seed packet. This will allow sufficient air circulation for humidity control.
• Use balanced vegetable fertilizer. Use it only when required. Too much nitrogen will cause flower formation.
• Keep the plants protected from dry spells and extreme hot and cold temperatures.
• Prevent overmaturity by blanching the cauliflower. Cover the developing head with leaves and tie the leaves to blanch the cauliflower. Once the curd grows to the size of an egg, it is the right time to start blanching. You may need to adjust the position of leaves for maximum protection as the head grows.

Fungal Diseases

Virus and bacterial diseases can cause discoloration of the cauliflower head. It can turn pink, purple, yellow, brown, or even black. However, it should not be difficult to distinguish between viral or bacterial diseases and purple discoloration due to other reasons already discussed in this article.

The color change due to diseases will be dull, unattractive, or rotten looking. Can even have foul-smelling areas and leaf wilting. This is entirely different from attractive pink or purple color change due to temperature fluctuation. 

Most diseases thrive in warm, damp conditions. Too much rainfall or excessive watering promotes the growth of bacteria and fungi. 

Solution – Prepare And Control!

• Plant varieties that are resistant to major Brassicaceae family diseases. These include bacterial leaf, black rot, club rot, mosaic virus, and white mold.
• Plant cauliflowers in well-drained soil.
• Avoid watering the curds. Water the soil around the plants instead.
• Apply recommended amounts of fungicide if required and monitor the plants.

Is Purple Cauliflower Safe To Eat?

A simple purple cauliflower with no signs of disease or insect infestation is OK to eat. You can eat it raw, roasted, grilled, steamed, or sautéed.

During the cooking, the purple color may leach out, and the hue of the cauliflower will turn gray, light green, or slightly blue. This is normal and will taste just like ordinary white cauliflower. 

It is better to discard the curd if you notice disease-like mushy blemishes, brown, blackish spots, or foul-smelling areas. This means it is not safe to eat.

What Does Purple Cauliflower Taste Like?

The purple coloration does not affect the cauliflower’s taste or texture. It only affects appearance. So, the purple cauliflower will taste mild, sweet, and nutty, just like white cauliflower.

Is Purple Cauliflower Better Than White?

Although both purple and white cauliflowers are high in nutrients, purple cauliflower contains more anthocyanins. Anthocyanins possess anticancer, antimicrobial, antidiabetic, anti-inflammatory, and anti-obesity effects and can prevent cardiovascular diseases. [2]

Below is a table of the nutritional value of cauliflowers (100 g). [3]

5 Tips On How to Grow Big Cauliflower Heads at Home

Final Thoughts

Let’s sum up what we discussed so far.

There are 5 reasons why cauliflower can turn purple:

• Temperature
• Soil Nutrients
• Cauliflower Variety
• Ricing
• Fungal Diseases

But the main reasons are temperature and soil nutrients.

If you take care of these two, you should have a lovely white curd. Well… Unless you have a purple variety, of course.

If you don’t want white curd and want to experiment a bit, try purple varieties or plant white varieties in the summer heat. The sunlight will intensify the color.

Hopefully, you got the answer to why my cauliflower is turning purple. If you enjoyed reading our article, check out other similar articles in our Gardening How To section.

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