Cauliflower is a cool season crop that needs consistent temperatures in the 60s to grow a healthy head. In hot weather, it may “button,” or grow many small heads instead of one large one. Cauliflower prefers full sun, but will tolerate some shade, especially in warm weather. It needs well-draining soil with a pH between 6.0 and 7.0. To increase the fertility of your soil before planting, mix in up to four inches of mature compost. If your soil is in particularly poor condition, add additional high-nitrogen fertilizer to enrich the soil. Organic fertilizers like alfalfa, cottonseed meal, and aged manure are good choices when planting cauliflower.
For a spring or early summer harvest, start your cauliflower indoors 6-8 weeks before your last frost date, and transplant the seedlings into the garden about 3 weeks before the last frost. Your transplants should ideally be about 4” tall when they go in the garden. For a fall harvest, find the days to maturity for the variety you’re growing, and then plant seeds that many days before your area’s first frost date. If you use floating row cover, you can cheat your planting date later by several weeks. In some climates, it’s possible to direct seed fall cauliflower crops outdoors, but in hotter climates such as the Southeast, it’s often too hot out for cool-season plants to thrive when fall seeding time rolls around. Starting your fall cauliflower seeds under shade cloth or indoors in the AC may be best.
When transplanting, space your plants 12-24” apart in rows 36” apart. Apply an organic mulch made of mature compost, leaves, or bark to keep weeds in check and soil temperature regulated. Cauliflower plants have very shallow roots. If you disturb the soil, you may accidentally break roots and damage the plants. If weeds develop around the plants, suffocate them with mulch instead of plucking them from the ground to avoid disturbing the cauliflower’s roots.
Allow your plants between one and one and a half inches of water per week. Cauliflower likes moist (but well-drained) soil. In particularly hot or dry conditions, increase the amount of water you give your plants. Fertilize your plants about three weeks to one month after transplanting. Fish emulsion works well for fertilizing cauliflower plants.
When the heads (or “curds”) reach 2 to 3 inches in diameter, they should be blanched (protected from the sun) to keep their bright white color. Self-blanching varieties should take care of this for you, by growing leaves that wrap around the curds. If the curds are not well-covered naturally, you can tie the outer leaves up around them. Harvest when the heads have reached expected size but are still mostly smooth. Rough-textured heads are past their prime and won’t have the expected mild flavor and tender texture. Pay attention to the variety’s days to harvest, and check your cauliflower plants often as the expected harvest date approaches.
Cauliflower (Brassica oleracea) is an insect-pollinated biennial that needs only very mild winter conditions to trigger flowering. Early spring-planted crops will usually bolt, but fall-planted crops will not flower and go to seed until the following spring. To collect pure seed, isolate your cauliflower by ½ mile from any other B. oleracea varieties that may be in flower at the same time. Collect seed from at least six different plants to ensure good vigor and genetic diversity. A common seed saving method among home gardeners is to harvest the main heads from the plants, then allow the side shoots to flower and go to seed. Pick seed pods off the plants as they turn brown and completely dry. You can open them and empty out the seeds by hand, or crush the pods all together and then winnow by pouring the seeds and chaff from one container to another in front of a fan. Make sure the seeds are completely dried before storing them in an airtight container in a dark and cool location.