Tips for Growing Cauliflower (and Preventing Common Problems)

Woman Holding Fresh Cauliflower

Cauliflower is perhaps riding its highest wave of popularity ever, thanks to its versatility for those following low-carb or keto diets. Growing cauliflower requires a fair bit of planning and diligence, but it can definitely be done.

When to Plant Cauliflower

The single most important thing to remember is that, when growing cauliflower, timing is critical. If the temperatures consistently reach higher than 65°F (18°C) while the heads are forming, you won't get much of a harvest. So, you have to time it correctly. Cauliflower transplants should be planted out in your garden two to four weeks before your last spring frost date.

Start Seeds Indoors

If you're starting cauliflower from seed, the seeds should be started indoors, under lights, four to five weeks before your last frost date. As Barbara Damrosch and Eliot Coleman note in their book The Four Season Farm Gardener's Cookbook, transplants shouldn't be any older than three weeks before they're set out, or growth will stop.

Transplant Carefully

To say that cauliflower is finicky is a bit of an understatement. Transplants should be set out young, before your frost date, but they can't take a freeze. A week of temperatures below 45°F (7°C) will make them go to seed, and too many days over 65°F will result in almost no heading. So what's a gardener to do?

organic cauliflower cluster

Creating the Right Conditions for Growing Cauliflower

There are a few steps to getting your cauliflower off to a good start.

  1. Sow cauliflower seed indoors five weeks before your last spring frost date.
  2. After two weeks growing under lights, start hardening them off for a week outdoors.
  3. At three weeks old, plant the seedlings directly in the garden. It's important to plant them in a place where you can give them some protection from frost, either by placing cloches or cut off milk jugs over the seedlings when there's danger of a freeze, or where you can cover the entire area with a floating row cover to protect it from freezing.

This process and planning for protection should help you get the timing right and protect the young seedlings from freezing.

You can also sow a fall crop of cauliflower by starting the seeds six to eight weeks before your first fall frost. The trick here is protecting them from late summer heat. Use shade cloth to offer a bit of protection on the hottest, sunniest days.

How to Plant Cauliflower

Once you have your timing figured out and your seedlings are ready, it's important to provide your plants with the best conditions for optimal growth. Cauliflower needs:

  • At least six hours of full sun per day
  • Nutrient-rich soil (it's a fairly heavy feeder)
  • Evenly moist soil

At planting time, amend your soil with compost and a balanced fertilizer. Plant cauliflower 18 to 24 inches apart, and water them in well.

Keep an eye on the weather. If a freeze is in the forecast, be ready to protect your seedlings with recycled milk jugs, cloches, or row cover. In a pinch, even an upturned cardboard box will work, as long as it's only left on overnight and removed early the following day.

Growing Cauliflower

Once plants are in the garden and dangers of freezing have passed, the main things you'll need to do for your cauliflower is water regularly, feed monthly with a balanced fertilizer or a side dressing of compost, and keep en eye out for insect pests. Once heads start to form, you'll know you're about a week to ten days away from your cauliflower harvest.

Blanching Cauliflower

If you're growing a white-headed cauliflower, you'll need to do what is known as "blanching" to make the heads white instead of a mottled greenish-brown. Unblanched heads also tend to be more bitter. If you're growing a colorful variety, such as a yellow, orange, or purple cauliflower, blanching isn't necessary, since it actually needs sunlight to develop those vibrant colors.

Cauliflower

How to Blanch Cauliflower

When you notice that the head is about two to three inches in diameter, pull up the leaves forming around it so they surround the newly forming head.

  • Secure the leaves closed with a clothes pin, clip, or tie with some twine.
  • Check regularly to make sure the leaves stay closed around the head.
  • This will keep sunlight off of the cauliflower and ensure that it develops a pure white color and milder flavor.
  • It takes about seven to ten days after blanching for a head of cauliflower to fully form. Most varieties are ready to be harvested 75 to 80 days after they've been transplanted in the garden.
  • Sometimes the head doesn't form right, stays loose, and never really firms up. Most often, the reason for this is that the conditions got too hot or dry during head formation.

Harvesting Cauliflower

If the heads are covered with leaves, how do you know when it's time to harvest? As mentioned above, it's usually ready seven to ten days after you've blanched the newly forming head, which has been growing inside the cocoon of leaves you've made for it.

The heads should feel compact and firm and be about six to eight inches in diameter.

Cut the head of cauliflower from the plant and ideally eat or preserve it within a day or two - cauliflower doesn't last very long in the refrigerator.

Cauliflower Pests and Diseases

Cauliflower is susceptible to many of the same pests as other brassicas family plants, including the following.

Cabbage Worms

Cabbage worms are the green larval stage of cabbage white butterflies. Handpick these when you see them on your plants, or cover your cauliflower with a floating row cover to keep the butterflies from laying eggs on your plants.

Aphids

Aphids can be an issue. If you see these tiny insects along the stems and undersides of leaves, give the plant a strong blast of water from the hose, or spray it with insecticidal soap. You can also wipe down the leaves and stems with a cloth dipped in soapy water. This will have to be done every few days until the aphids are completely gone.

Powdery Mildew

Powdery mildew is often an issue during periods of heavy humidity. To get rid of it, you can spray any infected foliage with a mix of 1 tablespoon of baking soda diluted in a quart of water. Douse infected areas well. If there are leaves that are beyond saving, prune them from the plant and dispose of them to keep the mildew from spreading.

Cabbage Root Maggots

Cabbage root maggots bore into and feed on the roots of brassicas plants, including cauliflower. They then pupate, turning into cabbage root flies. If you notice wilting leaves and a blue or yellow cast to the leaves, and the wilting isn't improved with watering, there's a good chance your plant has been infested. Possible solutions:

  • Sometimes, you can carefully dig the plant up, swish the roots in a bucket of cold water to dislodge the maggots, and then replant. If the roots have taken too much damage, the plant will likely die.
  • You can prevent the flies from laying eggs by installing traps or installing root collars, which make it hard for the flies to find a good spot to lay eggs.
  • Both of these solutions, however, have to be done as preventative measures at planting time.
Organic Cauliflower plant

Club Root

Club root is a disease caused by a soil-borne fungus that results in the roots of brassicas plants becoming swollen and eventually cracking and rotting, making them unable to absorb water and nutrients. If your plants wilt during the day, despite adequate watering, and the leaves turn yellow or purplish, and the plants just generally struggle along, it's a good chance they may be dealing with club root.

  • The fungus can last in the soil for up to 20 years and will infect any member of the brassicas family planted there.
  • Crop rotation is essential, being sure not to plant brassicas in an area where you've had issues with club root.
  • Be sure to sterilize any garden tools after using them to avoid infecting other areas of your garden.

Grow Your Own Cauliflower

While growing cauliflower isn't necessarily easy, it's certainly worthwhile. This tasty white veggie has many culinary uses, and growing your own is a great way to enjoy it fresh from the garden when it is in season.

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Tips for Growing Cauliflower (and Preventing Common Problems)