- Grow where you have not grown related crops—cabbage, cauliflower, broccoli, Brussels sprouts, collards, kale, mustard, turnip, rutabaga—for the past four years.
- For spring-planted cauliflower, start seeds indoors in April.
- For the fall crop, start seeds in July, indoors or direct seeded in the garden.
- Grow in rich, moist soil without drought stress.
- Blanch white cauliflower. Green, orange and purple types need sunlight to develop color.
Cauliflower (Brassica oleracea var. botrytis) is the same species as broccoli, cabbage, Brussels sprouts and turnip, and has many similar needs for good garden performance. For the best quality cauliflower, grow it in rich, moist soil without drought stress.
For those who love it, nothing is better than the richness of cauliflower in an Indian curry, a North African stew, or a creamy soup. In many Minnesota kitchens, raw on a vegetable platter, steamed as a side dish, baked in a cheesy casserole, or pickled and served with a sandwich are all common recipes.
The dense, mounded head of cauliflower is the “curd.” The curd is the flowering stalk of the plant. The edible stage is before the flowers open. Dense, flavorful curds grow in cool temperatures, between 50°F and 70°F.
Some varieties are good for spring planting, growing quickly and producing curds before hot summer weather sets in. Most types are best as a mid-summer planting for fall harvest.
Warm weather during growth of the leafy portion of the plant helps build a large plant, leading to a larger head. Pointy, green Romanesco cauliflower is a fall crop.
Gardeners in the far northeastern part of Minnesota, from Duluth north, can grow excellent quality cauliflower all summer long.
Soil pH and fertility
- 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.
How to keep your cauliflower plants healthy and productive
- 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.
- Imported cabbageworm, cabbage looper, and diamondback moth larvae feed on the leaves. Young seedlings and transplants are most vulnerable to injury from this feeding.
- Flea beetles chew small holes in leaves. Seedlings are vulnerable to injury from this feeding.
- Root maggots feed on the roots, injuring the plants, and in some cases even killing them.
- Although root maggots and flea beetles are more active early in the season, they can also severely damage small plants in mid-summer. Use a lightweight row cover to help prevent these pests.
A variety of diseases affects cauliflower, including Alternaria leaf spot, black rot, black leg and clubroot.
Many diseases arrive on infected seed. Always purchase clean, disease-free seed from a reliable source. Remove diseased plant material from the garden and destroy it, or bury it where found.
Use good cultural control practices to reduce disease problems to a good level and have a successful harvest.
Practice crop rotation. Choose a location in your garden where you have not grown related crops--cabbage, cauliflower, broccoli, Brussels sprouts, collards, kale, mustard, turnip, or rutabaga--for the past four years. Even if you have not noticed disease symptoms previously, it is best not to plant cole crops where other plants in the same family have grown recently. Disease spores in the soil can easily infect new plantings.
For assistance in diagnosing unknown problems, visit the University of Minnesota Extension diagnostic site “What’s wrong with my plant?”
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.
Reviewed in 2018