How to Grow Cauliflower
Two crops of cauliflower can be grown each year, one spring and one fall. Cauliflower is a temperature sensitive crop, with an ideal growing range between 60 and 70 degrees F. Cauliflower grown at temperatures below 60 F will yield less than cauliflower grown at temperatures near 70 F, so you need to plan your seed sowing date carefully. A good guideline is 4-6 weeks before the last spring frost and 12-13 weeks before the first killing frost.
Start cauliflower in propagation trays, preferably with separate cells for each seedling. 2-3" cells are ideal as you need to hold the transplants for 4-6 weeks, until they are about 6" tall and have 5-6 true leaves. Use a well-drained soil mix fortified with nutrients and feed regularly with a nitrogen-rich fertilizer, such as fish emulsion; once a week is not too frequent. Keep the transplants moist as they grow: do not let the soil dry out. Provide plenty of direct light.
When the seedlings are ready to transplant, choose a day that is cool and cloud covered. Just before rain is expected is ideal. Handle the seedlings with care to avoid damaging the roots and water in well as you go. Plant 18-20" between plants in the row with 30-36" between rows. The more space you allow between plants the faster they will mature. Well composted soil that is high in nutrients provides the best results. Water deeply at least once a week if rainfall is sporadic. Feed with fish emulsion about a month after transplanting.
Exposure to too much sun and heat will result in discolored spots on the heads. These blemishes do not change the flavor but they give it an unappetizing appearance. You can blanch the heads by tying the largest leaves over the heads with rubber bands or twine when curds begin to develop. Do this late in the day when the leaves are dry or you may encourage rot. Check every several days as heads may develop 3-5 days after tying in warm weather, or as long as two weeks when conditions are cooler.
Cauliflower is a shallow rooted crop and mulching is preferred over weeding to suppress weeds and avoid damage to the roots. Cultivating too close can damage the roots and set back the plants.
Harvest cauliflower when the heads are compact, about 6" in diameter, and still surrounded by wrapper leaves. While this may not be full size, the quality is superior to heads that are left too long. Cut with a knife, keeping a few leaves to protect the head. Kept in high humidity in cool conditions, the heads can keep for 4-5 days.
Aphids are a common pest of cauliflower, clustering on the leaves. Spray directly with water to remove them. Cauliflower is also a host plant for cabbage loopers, cabbage worms and other types of caterpillars. Their damage is visible as holes between the veins of the leaves and greenish brown frass which accumulates on the leaves and heads. Control these with the application of Bt (Bacillus thurengiensis) as soon as you see signs of damage.
Rotate the location of your cauliflower crop every year to prevent the build-up of pathogens in the soil.
Seeds may be kept for up to five years under good conditions.