When and How to Blanch the Heads of Mature Cauliflower

Cauliflower, Brassica oleracea var. Botrytis is a cool-season cruciferous crop that can be challenging to grow.

There are many different varieties available in shades of green, orange, purple and white.

White types need to shelter their heads in a process known as blanching to produce a crop with an icy color and sweet flavor.

This is not the same as the practice of boiling vegetables, steeping them in boiling water before plunging them into the ice bath that you are probably familiar with.

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Blanching is the simple practice of tying the large outer leaves together around a head of cauliflower to prevent them from turning yellow or brown and developing a bitter flavor due to sun exposure. Some older white varieties may also turn mottled purple.

In this short article you will learn when and how to blanch cauliflower with its leaves.

How to Blanch Cauliflower in the Garden

when the time is right

About a month after sowing, healthy cauliflower plants will be lush with leafy foliage. At this point, the first little heads should start to appear. If you’re just starting out, check out our guide to growing cauliflower.

Some cultivars, such as the ‘Early White Hybrid’, have leaves that curve up and outward away from the head. It does little, if anything, to protect the developing head from the sun.

These varieties require blanching by hand to prevent damage.

Others, such as ‘Snowball Self-Blanching,’ will naturally wrap their inner leaves around the mature ends.

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Often this is enough to successfully shelter them from intense rays, but they too can benefit from gardener intervention.

It may seem like a no-brainer to buy the self-shielding type.

However, considerations such as taste, head size, length of growing season and price may make other types more attractive to some gardeners.

When the seedlings reach the one-month mark, watch the plants closely, because for the most flavorful harvest, you should start them on a dry day protected from the sun before the heads are 3 inches across.

You can still produce an edible crop if you start late, or skip blanching altogether. However, the color of the curd may become discolored or even burnt in the sun, and the taste may be bitter.

How to go about it

If you’re not sure whether you have a self-blanching variety, look at how the leaves are growing. If they are wrapping around the developing head and effectively shielding it from the sun, you may not need to take any protective action.

However, if the leaves are growing upwards and away from the heads, this can leave your crops sensitive to the sun’s rays. In this case, you’ll need to take steps to get the leaves to cover the ends.

Here’s how to do it. It’s very simple. Imagine peeling a banana upside down.

1. Choose a large card to start with.

2. Gently fold the leaf inward over the center of the plant. Keep the leaf in place.

3. Grab the second leaf in the same way, and fold it over the center of the plant to meet the first. Hold the tops of both leaves together in one hand.

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4. Use your other hand to gently fold the third leaf inward to meet the first two. Hold all three leaves together in one hand above the center of the plant.

5. If necessary, fold a fourth leaf inward to meet the other three, effectively hiding the developing head.

Photo by Russell Lee. Wikimedia Commons via CC 3.0

6. Use twine, rubber bands, or clothes pins to loosely tie together the leaves you’re holding together. Secure them either at the top or in the middle, so that they drape over and around the head, covering it completely.

Imagine peeling a banana upside down again. We have to keep the open peels closed.

However, we need to leave some room for airflow, to monitor progress, and to allow the head to reach mature dimensions of six to eight inches in diameter. That’s why we tie them loosely.

Alternative methods include bending the large leaves over the head until they touch the ground, and weighing them down with a brick or rock, or placing a large container over the entire plant.

I’m not a fan of these methods for two reasons:

First, they can reduce airflow and lead to fungus growth.

And second, by corroding the ground, it can create a moist spot that is attractive to munching slugs and snails.

Here’s a tip: Blanch on a dry day, after the morning dew has evaporated. This way, no moisture gets trapped near the curd and mold growth is prevented.

Thats all there is to it!

harvest ready

Check the developing heads every few days by peering between the leaves. Keep an eye out for any hidden pests and treat as necessary. Learn more about controlling cauliflower pests here.

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In one to three weeks, they should reach their mature size and be ready to harvest. When the time is right, simply open the leaves to reveal your harvest.

Also, if your self-blanching varieties don’t seem to have enough foliar cover, or if you’re experiencing a heatwave, don’t hesitate to collect and tie off their outer leaves to prevent discoloration of the heads.

Read more about harvesting cauliflower here.

Crisp and white for your cooking pleasure

Blanching is an easy technique you can use with confidence to preserve the color and flavor of the foliage. Asparagus and celery are two other vegetables that are often blanched to lighten their color and sweeten their flavor.

Add cauliflower to this year’s garden planner, and get ready to reap the benefits of a challenging crop grown well!

And be sure to visit our sister site, Foodle, for more delicious and nutritious cauliflower recipes.

We love to hear from our readers. Do you have any advice for cauliflower growers? Have you tried whitewashing your crops in past years? Please share your stories in the comments section below, and don’t forget to tell us what areas you’re growing in!

Learn more about growing cauliflower with these helpful guides: :

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