Provide at least 1 inch of water a week, soaking the soil to a depth of 6 inches. Cauliflower requires constant moisture to produce large, tender heads; soil that dries out between waterings will cause heads to open up and become “ricey.” Use a thick layer of compost or organic mulch to cut down on evaporation and weeds and to cool the soil. Be careful not to disturb cauliflower roots when weeding, because damaged roots produce uneven growth. Give young plants monthly light feedings with fish emulsion or compost tea. If you want to speed up growth, feed every 2 weeks.
When the flower heads (curds) of white-headed cultivars are about the size of an egg, blanch them by shading out the sunlight. Otherwise they’ll turn yellowish or brown and become, if not less tasty, certainly less appealing. Prepare plants for blanching on a sunny afternoon when the plants are totally dry, because damp heads are more susceptible to rot. Just bend some of the plants’ own leaves over the head and tuck them in on the opposite side, or secure the leaves at the top with soft twine, rubber bands, or plastic tape. Use enough leaves to keep out light and moisture, but allow room for air circulation and for the heads to grow.
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Once the blanching process begins, be careful to avoid splashing water on the heads or leaves. Unwrap occasionally to check on growth, to look for pests, or to allow heads to dry out after a rain. In hot weather, heads can be ready to harvest in a matter of days. In cool periods, the maturing process can take as long as 2 weeks. Blanching is not necessary when you’re growing varieties that produce purple, lime green, or orange heads, or with self-blanching types, which have leaves that naturally curl over the head.