Cauliflower (Brassica oleracea, Botrytis group) is also called "heading broccoli". It is a type of cabbage that originated in southern Europe. For many gardeners, cauliflower is one of the most temperamental crops to grow in the vegetable garden. Unlike broccoli which produces side shoots for additional harvests, there is only one opportunity for a good crop with cauliflower because the plant produces only one head. The head, sometimes referred to as a "curd", is formed from shortened flower parts at the top of the plant.
There are several reasons why cauliflower can be tricky to grow in a home garden - most of them due to environmental factors. Too much heat prevents the cauliflower head from forming. Cauliflower must be grown at a continuous, steady rate through it entire life, from seedling to harvest. Anything which slows or stops its growth, such as insects, lack of water, or excessive heat or cold, may prevent development of the head.
Some plants may produce heads prematurely on relatively small plants. This occurrence, called "buttoning", is frustrating to gardeners. It is caused by any type of stress that interrupts the plants growth. It often occurs when large transplants, or those crowded in cell packs and flats, are planted into the garden. Setting cauliflower plants outdoors when temperatures are still cold may also be a problem. To avoid "buttoning", plant small, healthy transplants two weeks before the average last frost date in your area. In young cauliflower plants, there is a fine balance between vegetative and reproductive growth. Any stress tips the balance toward button formation.
Success with growing cauliflower begins with selecting a variety that performs well in Iowa. Varieties that require a growing season of 50 days or more are recommended. Early maturing varieties are more susceptible to buttoning than later varieties. 'Snowcrown' hybrid, which matures in 60 days, is an excellent variety for home gardens.
Cauliflower is usually set out as transplants that were started indoors 6 to 8 weeks before planting. Cauliflower transplants are easy to grow. Sow the seed 1/4 inch deep in individual containers, such as peat pots, or in furrows in flats and later transplant the seedlings to individual containers or cell packs containing fresh, well drained potting soil. The optimum soil temperature for seed germination is 80 F., however, cauliflower will germinate at temperatures as low as 50 F. After germination, set the seedlings in a location that receives direct sun or grow them under artificial lights. The growing temperature show be approximately 60oF. Keep the soil moderately moist, but not soggy.
Harden-off the transplants before planting them in the garden. About 5 days to a week before planting, set them outside in the shade and gradually expose them to longer periods of sun. Plant the young transplants in the garden on a cool, cloudy day or late in the afternoon. It is a good idea to apply a starter fertilizer at planting time. Plant cauliflower two feet apart in rows 30 to 36 inches apart.
Cauliflower grows best during sunny days with air temperatures of 70 F. If temperatures are above 80 F. during curd formation, leaves may form in the head, it may become rough in texture, or have a purple or green coloration.
When the head is golf to tennis ball size (2 to 3 inches in diameter), it needs to be protected from sunlight. This keeps the head white, protecting it from sunscald and turning yellow and off-flavored. Tie the outside leaves loosely over the head with a strip of old nylon stocking or soft cloth. Some gardens use spring-type clothespins to tie the cauliflower leaves up.
The heads will be ready for harvest one to two weeks after covering, depending on the weather. Check the head every few days so that it does not become overmature. Harvest cauliflower heads when they are six or more inches in diameter but before the flower parts separate.
For fall plantings, transplants are started in early July and set out in the garden in early August. Mulch around the young plants and keep them well-watered.
This article originally appeared in the February 28, 1997 issue, p. 16.