Broccoli is the easiest of the cole crops (cabbage and its close relatives) for the home gardener. Probably a Mediterranean native, this cool-season crop grows 23 ft. tall, with a branching habit. Its central stalk bears a cluster of green or purple flower buds; when that cluster is removed, side shoots lengthen and produce smaller clusters. Many Southerners grow two crops each yearone in spring and one in fall. To produce the mammoth heads you admire in seed catalogs or the grocery store, you'd need longer periods of cool weather than we have over most of the South, but you can realistically expect heads to grow to 48 in. across.
To get a jump on the growing season, always start broccoli from transplants (you can buy them at the garden center or grow your own from seed in cell-packs). Broccoli doesn't grow well after warm weather arrives in spring, and a hard freeze in fall will kill it. For a spring crop, set out seedlings 4 weeks before the last frost; for a fall crop, plant in late summer or early fall. In the Coastal South (USDA 9), plant between September and March; in the Tropical South (USDA 10-11), plant between September and January.
For spring planting, choose early-maturing types, so the heads will form before hot weather arrives. Try 'Di Ciccio' (50 days from transplanting to harvest), 'Green Comet' (55 days), 'Green Duke' (50 days), 'Green Goliath' (55 days), 'Packman' (57 days), and 'Premium Crop' (58 days). All of these are also good for fall planting. In the Coastal and Tropical South, late-maturing 'Waltham 29' (80 days) is another good selection for fall planting. Production of side shoots is usually more dependable in fall. Selections noted for extended production of side shoots include 'Green Comet', 'Packman', and 'Waltham 29'. For Romanesco, see Cauliflower.
Broccoli needs fertile, well-drained soil. Set transplants 1112 ft. apart in rows 23 ft. apart. Feed with water-soluble 20-20-20 fertilizer. Three weeks after planting, sprinkle 12 cup of 10-10-10 fertilizer per 10 ft. of row around plants. Water regularly to maintain steady, rapid growth; don't let the soil dry out. Harvest when the hundreds of tiny flower buds that form the head are still green and tightly closed; a head showing yellow flowers is past its prime. Cut the stem 56 in. below the head. Side shoots are usually ready to harvest 2 to 3 weeks after you cut the central headbut if the weather gets too warm, they'll quickly bloom.
A number of pests plague broccoli; they are usually more troublesome in spring than in fall. To prevent a buildup of soil-borne pests, plant in a different site each year. Club root is a serious fungal pest in acid soils; apply lime, if necessary, to raise the pH to at least 6.5. Floating row covers do a good job of controlling insects such as cabbage loopers, cabbageworms, cutworms, and root maggots. You can also control cutworms and root maggots by ringing the base of the plant with a collar made from cardboard. Bacillus thuringiensis (Bt or spinosad) applied according to label directions controls cabbageworms and loopers.