Cauliflower is an easy to grow, tasty and nutritious vegetable. There are two phases in the growth of the cauliflower plant: vegetative and reproductive, both of which are necessary for healthy cauliflower plants. It is desirable to have good vegetative growth before the reproductive (head) growth. During the growth period the plant is very sensitive to changes, while if in the vegetative phase the plant is upset, head formation begins Early head formation results in a small plant with small `curds'- which is known as "buttoning" or early heading. Examples of changes (stresses) are: cold soil or air temperatures in the spring, a lack of fertility or water, the use of transplants with poor root growth or rootbound transplants, and insect damage and disease.
Varieties that mature in a short time after transplanting are more susceptible to the stress than varietes that require a longer period to mature. Properly grown transplants, adequate fertility, regular irrigation, and good insect and disease control ensure a successful crop.
Hot, dry weather can cause several physiological problems. "Leafy heads" occur when the leaves grow through the head, forming individual segments surrounded by leaves. Often, the heads are also "ricy" (the surface has a granular appearance) or "hairy" (the small floret parts begin to expand). Tipburn on young cover leaves is common in early cultivars. This problem usually appears just before or as heads begin to form. It appears to be most prevalent in unirrigated fields but also occurs in well watered fields. Tipburn may be caused by calcium deficiency as a result of rapid growth during hot, dry weather. It also appears to be related to molybdenum deficiency. Tipburn appears to be similar to internal tipburn in cabbage and blackheart in celery. Later maturing cultivars are not affected as much because they head during cooler weather when plants are growing slower. To avoid or to overcome these problems, continue irrigation until the heads have been harvested. Apply molybdate (3 ounces per acre) weekly. Although calcium may be involved, there is no evidence that foliar applications of calcium will help.
Molybdenum deficiency occurs in broccoli, cabbage, and cauliflower. Recently matured leaves are uniformly pale green, while older leaves maintain their dark green color. Young, developing leaves affected by this disease do not expand properly, often causing oddly shaped leaves. The leaves curl over, with yellow fringing on sides or tips of leaves. The yellow areas become brown (necrotic) and soft rot often sets in. The soft rot on the inner leaves usually discolors the heads, making them unusable. Although the plants usually produce an acceptable head, often not enough large leaves are able to cover and tie the heads.
The application of 3 lbs. of sodium molybdate per acre per week as a foliar spray is helpful in combatting Molybdenum deficiency. Application should continue until the symptoms disappear. This chemical can be included in insecticide sprays.
Calcium deficiency may appear in midsummer, often in fields with pH's below 5.0. Symptoms include: interveinal chlorosis in old leaves, a purpling and stunting of very young leaves, and, in some plants, the death of the growing point.
This disease may be remedied with the application of 10 pounds of calcium chloride per acre, or with 15 pounds calcium nitrate per acre in a foliar spray of 40 or more gallons per acre. A non-ionic surfactant should be included with the spray mixture. One or two applications should overcome the disease.
Cole crop plants develop slowly and often appear to stop growing before nitrogen deficiency symptoms appear. These crops should be sidedressed two to four times with 30 to 50 pounds of actual nitrogen per acre each time. Heavier, darker soils can be sidedressed less often with extra nitrogen. When heavy rains or irrigation occur, thus leaching soluble nutrients such as nitrogen, sidedress more frequently.
On occasion, cauliflower heads show fuzzy projections on the surface. These projections are bracteoles that form and develop around each flower bud primordium. Such formations occur when the developing heads are exposed to temperatures higher than optimum for curd development. Leafy heads, in which green leaves grow through the surface of the curd, occur when the cauliflower curds are exposed to temperatures higher than those inducing fuzzy heads.
A warm, dry summer with sufficient rainfall results in good foliar growth with few disease problems. By early to mid- September, when most varieties should be heading, some plants may be still actively growing vegetatively. Mid and late season varieties, which normally head by early October, may not head at all. In these cases, the problem seems to be the opposite of buttoning (premature heading). Normally, cauliflower forms a head as a result of stress: buttoning can occur any time during the season after the plants have been stressed.
If conditions for foliar growth are nearly ideal, heading may not occur at the usual age of the plants. Cool night temperatures in September may trigger heading, however, if night temperatures do not reach normal lows until well into October, heading may be delayed. Daytime high temperatures below normal for several weeks in late September and October cause the plants to grow slowly, so it may take the heads three to four weeks to mature. Under these circumstances, late plantings of late varieties such as Starlight, Christmas White, and Self-Blanche, probably would not produce a crop.
Cauliflower still in the field can be harvested until it is damaged by frost - it can take some frost but should not be harvested while frozen. A frost of two or more hours below 25 degrees F will normally discolor cauliflower so that is is no longer salable, although still good to eat.
Cauliflower for earlier production generally results in good production under headless cauliflower situations. It may be prudent to make two transplantings of several varieties, the first around June 15 and the second around July 1. This would ensure a steady supply of cauliflower from September 1 and on.
Hortopics: 11/83, by B. Zandstra.
Hortopics: 12/83, by S. Honma.
Compiled from articles by B. Zandstra and L. Taylor, Michigan State University Dept. of Horticulture.