Cabbage, Broccoli, and Other Cole Crops

Fertilization

Harvesting a ton of cauliflower removes 3 to 10 pounds N, 2 to 4 pounds P2O5, and 5 to 7 pounds K2O from the soil. Fertilizer recommendations are given in Cole crop nutrient recommendations based on soil tests, but cauliflower is also subject to micronutrient disorders. Molybdenum deficiency in cauliflower results in a disorder called 'whiptail'. In severe cases leaf blades consist of only midribs and the growing point is so deformed no head develops. Molybdenum deficiency is found most commonly where the pH is low and soil manganese is high. It can usually be prevented by liming to a pH of 6.5. See Chapter 1 for a discussion on liming and organic sources of the fertilizer requirements given in this table. Like all cole crops, cauliflower has a relatively high boron requirement. Low boron levels result in blackened, hollow stems and water-soaked, brown spots on the curd.

Planting

Unlike broccoli, cauliflower is never bunched. While the head size desired may vary somewhat with the market, typically the harvested head measures 6 inches in diameter and weighs 2 to 2.5 pounds. Generally this head size can be achieved by planting on ridged rows 36 to 42 inches apart with 15 to 20 inches between plants. As with broccoli, fall crops tend to have higher quality in the southern states.

Blanching

If cauliflower curds are exposed to sunlight during development, peroxidase activity is stimulated and curd color is yellowish rather than pure white. Although there are self-blanching cultivars, in most cultivars the curd must be shaded by loosely tying the leaves together once the head is 1 to 2 inches across. This also reduces the heat load on the curd.

Color-coded rubber bands used for tying allow heads to be harvested at the proper stage of development without individually inspecting each head. The time from tying until the shaded head reaches full size ranges from 5 days in warm weather to 15 days in cold weather. Several heads are untied each day and inspected to determine if they are large enough to be harvested. In 1989 a green cauliflower was introduced. Although marketed as 'Broccoflower', it is actually a green curd cauliflower that does not have any properties of broccoli except that it need not be blanched. Purple curd cauliflower (which turns green when cooked) is also available.

Harvest

Cauliflower is harvested when mature heads are fully developed, compact and 6 inches in diameter. In preparation for marketing, the heads are cut just below the curd and the leaves enfolding the curd trimmed to 2 inches. Cooling to 33 degrees F is required as soon as possible after harvest, and shipments are iced during transport to preserve quality. Ice should not be in direct content with the cauliflower, however, or head spotting will occur. Approximate storage life under these conditions is 3 to 4 weeks. A good yield would be 7 to 8 tons per acre.

Special Considerations

Nearly three-fourths of the cauliflower grown in the United States is grown in the coastal valleys of California where temperatures and other environmental conditions are fairly constant over the growing season. The variable temperatures and moisture levels of the southern states are far from ideal for cauliflower production, especially in the spring. Some of the problems caused by this environmental variability are presented in this section.

Temperature is particularly critical for successful production of cauliflower. Transplants exposed to cold are large and thick stemmed with attached leaves. The growing point may be killed, by cold or other stresses, resulting in 'blindness'. As with broccoli, 'buttoning' or premature development of a small curd on young plants can also be caused by stress: cold, too wet or too dry soil, nutrient deficiencies, and weed competition. Early maturing cultivars such as 'White Contessa' and 'Stovepipe' are most susceptible.

Once the juvenile stage is passed (stem almost the diameter of a pencil), temperatures of 63 degrees F are needed for best curd formation. If temperatures are too high (over 68 degrees F), poor quality curds are formed. Temperatures too low during curd development cause internode elongation and open curds. In fact, any stress that slows growth will decrease the head quality, making them small or open. Fluctuating temperatures and moisture will also cause less compact growth. Even after the head is formed, high temperatures cause a reversion to vegetative growth with production of bracts on the head. In a marketable cauliflower head, the individual flower buds are undeveloped and undifferentiated. High temperatures (as when the head is exposed to direct sun), too rapid growth after the head is formed, high humidity or high nitrogen cause 'ricing' wherein the flower buds develop, elongate and separate, making the curd unmarketable.