Growing cauliflower in home gardens

• Have your soil tested. 
• Grow cauliflower in well-drained yet moisture-retentive, fertile soil with pH of 6 to 7. A good cauliflower crop needs this ideal garden soil.
  • Apply phosphorus (P) and potassium (K) according to soil test recommendations.  
  • Many Minnesota soils have enough phosphorus. Unless your soil test report specifically recommends additional phosphorus, use a low- or no-phosphorus fertilizer.
• It is not worth growing cauliflower unless the plants absorb water and nutrients steadily during their growth.
• Improve your soil by adding well-rotted manure or compost in spring or fall. 
• Do not use fresh manure as it may contain harmful bacteria and increase weed problems.
• If you use manure or compost, you may not need more fertilizer applications, depending on how much organic matter you use.
• Side-dress when the plants are about four inches tall.
• Do not use any fertilizer containing a weed killer ("Weed and Feed"), as it may kill your vegetable plants.

For spring-planted cauliflower, it is best to plant in early to mid- April. Choose a variety with heat tolerance and a short growth cycle (50 to 60 days to harvest). ‘Snow Crown’ is one of the best for spring growth.

For the fall crop, start seeds indoors or direct seed in the garden, in early to late July.

Whether you plant in spring or summer, a row cover will protect the plants from wind and insects during the first weeks of growth. In spring, use a cover material that will give protection against cold. In summer, use a lightweight material so that temperatures do not get too hot under the cover. 

If strong winds loosen a floating row cover, it can do more damage than the plants would suffer without it. Be sure to anchor it firmly with soil and/or pins at the edges. Alternatively, support the row cover with wire hoops, forming a low tunnel.  

• Use sterile soilless seedling mix and press the seeds one-fourth to one-half inch deep.
• Do not use bottom heat. The seeds will germinate and the plants will grow well in summer temperatures.
• Seeds should germinate in about two weeks. Turn on bright grow lights above them once the seedlings emerge.
• Apply fertilizer to developing seedlings beginning when the first true leaf appears. Use a half-strength starter solution once a week. After two true leaves are present, apply fertilizer twice a week.
• When the plants have four or five true leaves, after about four weeks, begin hardening them off so that they will adapt well when transplanted outdoors. Reduce watering. Place plants outside where they will receive wind protection and a couple hours of sunlight.
• Gradually expose them to more sunlight and wind over the next week. Keep them well watered.
• Dig small holes with a trowel, or dig a narrow trench with a shovel. Place the seedlings 18 inches apart. Fill the soil around them so that the plant is at the same level it was in its pot.
• Water the plants in, or use a liquid starter solution high in phosphorus and low in nitrogen and potassium.
• Apply a row cover, if using.

• Direct seed cauliflower in July.
• Plant seed shallowly, one fourth to one-half inch deep, dropping three seeds every 18 inches.
• Keep the soil moist during seedling emergence.
• Once the plants emerge, thin so that one seedling remains every 18 inches.
• Take care of the seedlings. When small, they experience extreme heat, wind, drought, and insects. Water them as needed.

• Cauliflower needs good soil moisture. To produce hard, solid, rich-flavored heads, the plants must not experience water stress.
• If the plants do not receive consistent rainfall or irrigation, they will have poor texture and may develop strong “off” flavors.
• If the planting does not receive one inch of rain each week, soak the soil thoroughly at least once a week.
• If your soil is sandy, it is important to water more often than once a week.
• An inch of water will wet a sandy soil to a depth of ten inches, a heavy clay soil to a depth of six inches.
• Use a trowel to see how far down the soil is wet. If it is only an inch or two, keep the water running.

• Frequent, shallow cultivation with a hoe or other tool will kill weeds before they become a problem.
• Hoe just deeply enough to cut the weeds off below the surface of the soil. Be careful not to damage the plants when cultivating.
• Mulching with herbicide-free grass clippings, weed-free straw or other organic material to a depth of three to four inches can help prevent weed growth, decreasing the need for frequent cultivation.

To promote the color of white cauliflower, watch for the head to begin forming. Once it is visible, gather the outer leaves and tie them together over the head with string or rubber bands. This will keep the curds white-colored, or “blanched,” as they grow in a shaded environment.

There are self-blanching varieties available that do not require you to tie the leaves. They will still produce a white curd.

Do not tie leaves of colored—orange, green, purple—or Romanesco-type cauliflower. Full color will not develop on these types without sunshine on the curds.

• Harvest cauliflower when heads reach usable size, before the flower buds open. Cut the head above ground level and remove the leaves wrapped around the head.
• If you leave curds on the plant for too long, they will become loose, especially in spring plantings. Colder fall weather helps the later crop hold its quality in the field.
• Cauliflower will keep for about one week in the refrigerator. Even in colder, moist conditions, it will not keep more than three weeks.
• Preserve a big harvest by freezing cauliflower.
• You can also pickle cauliflower in a mix of vegetables.

Minnesota is home to many common insects that feed on cauliflower.  Some level of insect feeding it to be expected.

• Flea beetles chew small holes in leaves. Seedlings are most vulnerable to injury from this feeding.
• Imported cabbage worm, cabbage looper, and diamondback moth larvae feed on the leaves. Young seedlings and transplants are most vulnerable to injury from this feeding.
• Cabbage maggots feed on the roots, injuring the plants, sometimes killing them.
• Swede midge is a new pest in Minnesota that can cause cauliflower to produce no crown.

Many of the same cultural practices can help prevent various cauliflower diseases.  

• Alternaria is a common disease that causes spots on leaves and the crowns of cauliflower to rot.
• Black rot causes yellow triangles on the edge of leaves and can cause rot in the cauliflower crowns.
• Clubroot attacks cauliflower roots, causing roots to be swollen and plants to be stunted.

• Boron deficiency can cause the florets in the crown to turn brown.
• Plant stress, caused by nutrient deficiency, low moisture, or bad transplant timing, can cause immature plants to develop small heads.
• Hot weather (86°F in the day and over 77°F at night) can cause cauliflower to grow no crown. Plants may produce a crown if it cools off.