Growing Plants

Why Is My Cauliflower Turning Purple? — A Guide

Cauliflower may not be the easiest veggie to grow, but it’s certainly one of the most versatile in the kitchen (and nutritious!). With just a head of cauliflower, you can prepare dozens of tasty recipes.

However, if you take on the challenge and decide to grow cauliflower yourself, there’s a small chance that the plant may turn purple.

This unexpected change in color can be pretty alarming. Many readers have asked us, “Why is my cauliflower turning purple” before.

In short, it can be caused by various factors, from genetics to environmental conditions, like temperature or changes in soil conditions. Diseases or infections may even cause it.

In this guide, we will explore the reasons why cauliflower turns purple and what you can do to prevent it from happening.

Whether you are a seasoned gardener or just starting out, we hope the information in our article will be helpful!

Why Is My Cauliflower Turning Purple?

Why is my cauliflower turning purple
A “blushing” Snow Crown cauliflower

So what is purple cauliflowers?

These cauliflowers have specks, dots, streaks, or vast patches of purple on their curds instead of the familiar white.

As we said earlier, cauliflower can turn purple for different reasons, ranging from genetics to environmental.

Here are a few potential “culprits” that you can look into if you’re struggling with your cauliflower turning purple.

Temperature

Cauliflowers are best grown in temperatures between 60°F to 65°F (it is a cool-weather plant).

But if the weather doesn’t cooperate with you and a sudden cold snap drops the temperature in your garden down to 50°F, your cauliflower will react to protect itself.

This protection mechanism answers the “Why does cauliflower turn purple?” question.

The plant will secrete a chemical known as anthocyanin. It helps protect the plant’s cells from extreme temperatures better. And, as you may have guessed, anthocyanin is purple!

But it’s not just cold that can trigger anthocyanin production. Excessively high temperature beyond 70°F is also known to cause a few varieties of cauliflower to turn purple.

For example, Snow Crown cauliflowers are known to “blush” when grown during summertime.

This is the main chemical that’s responsible for the cauliflower purple shades.

So, while there are many reasons behind its production, anthocyanin is always the answer to every “Why is cauliflower purple …” question.

Sun Exposure

Too much exposure to the sun can cause the cauliflower to turn purple. Excess sunlight can kickstart the plant’s cells to produce anthocyanin.

It’s one of the reasons why many gardeners have taken to building sun shades for their crops.

Others prefer to wrap the leaves around the head of the cauliflower to shield it from sunlight (this method is called “blanching”).

Virtually all plants can be affected by the sun. For example, pepper plants can develop tiny black spots on pepper leaves if it’s overexposed to sunlight.

Soil Conditions

When soil conditions aren’t right and fertile enough, cauliflower can turn purple as a stress response.

This is the reason why some people opted to mess with the fertility of their planting ground to get their plants to turn a different, prettier color than white.

However, if you plan to do this, remember that it is not so simple.

You need a very good growing technique to pull this off because if you excessively starve out the plant too, it will turn a sickly yellow rather than a delightful purple.

Fungal Diseases

Fungal Diseases
A plant being affected by Blackleg

A fungal disease known as Blackleg, caused by the fungus Phoma lingam, can cause your cauliflower to turn purple spontaneously… but not in a delightful way.

The first signs of the disease are tan-colored spots on the leaves, which eventually darken to gray with black dots.

As the disease progresses, the stems may develop dark black to purple-bordered cankers or lesions, and the damage can move down the stems to the roots, blackening the tissue as it goes.

If your cauliflower is still young, being afflicted by Blackleg can cause it to wilt and eventually die. This is why it’s crucial that you prevent it from taking root in your garden.

Phoma lingam can produce fruiting bodies called pycnidia and pseudothecia.

They contain tiny spores dispersed into the air when the temperature is between 65°F to 80°F and conditions are wet.

Conveniently (for the fungi), this is the temperature range in that cauliflowers are grown. That’s why you should avoid planting while the weather’s wet.

Besides rotting cauliflower, Blackleg can affect other plants like zucchinis, causing them to wilt.

Ricing

If your cauliflower grows too quickly, a condition known as “ricing” may happen to it. When this happens, the curd (the big head of the cauliflower) will grow small, fuzzy flowers.

The fuzz will have a purplish or cauliflower pink color.

Since they affect the overall quality of the cauliflower, it’s best that you harvest the plant before ricing happens.

Cauliflower Variety

You’ve probably seen cauliflowers being sold that have the whole curd a deep purple color before. That cauliflower is most likely bred to have a splendid color.

Many varieties are selected for their ability to turn purple without requiring the gardener to put in too much work adjusting soil conditions or exposing it to harsh temperatures.

You can find many seed packets on the market: Sicilian Violet, Violet Queen, Rambo Purple, Purple Cape, etc.

There are plenty of choices out there. And no worries, anthocyanin isn’t harmful. It’s even beneficial for your health! (More on that later).

Steps to Take to Prevent Purple Cauliflower

If you dislike having purple spots on cauliflower, then there are a few things that you can do to prevent it from happening.

Grow Varieties That Are Self-Blanching

One of the reasons why cauliflowers turn purple is because of excess sunlight.

Self-blanching cauliflower varieties naturally form leaves that wrap around the developing head, shielding it from the sun and preserving its white color.

So, you don’t have to manually blanch the cauliflower by wrapping its leaves around its head with a cord.

Grow Varieties That Are Self Blanching
Many varietals of cauliflowers are self-blanching, meaning the leaves wrap around the head of the cauliflower, like in this photo

Schedule Ahead When You Plant

The best time for your cauliflowers to mature is around September and October, which is when the temperature is perfect for the plants.

You’ll be able to avoid the swelling heat of summer and the freezing temperature of late winter and early spring all in one fell swoop.

Remember, extreme temperature — in either direction, hot or cold — will cause your plant to produce anthocyanin.

Some varieties can mature as quickly as 60 days, so check the information on your seed packet to know when exactly to plant!

Avoid Temperature Spikes and Closely Control the Temperature

This one is a no-brainer. Check your area’s weather forecast regularly and take preventative measures when you hear of a heat wave or a cold snap.

You can install floating row covers to protect your plants from deep freezes and winds. Sunshades can be built to shield your plants from the sun during hotter months.

There are many techniques that you can use in anticipation of extreme temperatures. But the best method is to plan ahead and avoid the hottest and coldest months of the year.

FAQs

Now that we’ve sorted out the main question, “Why is my cauliflower turning purple?” … Let’s get to some of the smaller questions our readers asked us over the last couple of weeks about this subject.

See if they turn out to help and give you the info that you need, as well!

Does purple cauliflower taste different?

Anthocyanin doesn’t change the flavor or smell of cauliflower. It simply looks different!

Can I eat discolored cauliflower?

Anthocyanin is safe to eat. It’s even healthy to eat cauliflower purple spots! This chemical is antidiabetic, anticancer, anti-inflammatory, and antimicrobial and can help you lose weight.

It’s also a compound that can prevent cardiovascular diseases.

Which color cauliflower is best?

There is objectively no “best” cauliflower color. Anything other than black (spoiled or rotten) or yellow (overexposed to sunlight) is good.

In other words, white, purple, and pink cauliflowers are all good for you.

There are other kinds, too, such as blue cauliflower colors. These are also good to eat, and the cauliflower blue color is also caused by anthocyanin!

Conclusion

Purple cauliflower plants aren’t bad. The opposite, in fact, not only many people like the vibrant violet hue of cauliflower, but anthocyanin has also been found to be healthy for consumption.

But if you want your plant’s curd to have the standard pristine white color, we hope this guide has been useful in keeping your cauliflower from purpling!

Samuel Mark

Hello I am Samuel. Samuel's Garden is a garden blog where I share my experiences in garden caring and tree growth. Hope you enjoy it!

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