Start broccoli seed indoors 5 to 6 weeks before the last frost in spring. Transplant broccoli seedlings to the garden when they are 4 to 6 weeks old, as early as the last frost in spring, after hardening off the seedlings for 4 days. In mild-winter regions, start seeds indoors in late summer and set them in the garden in autumn for winter harvest. Broccoli will come to harvest in 55 to 85 days when grown from transplants and 70 to 100 days when grown from seed.
Description. Broccoli is a hardy biennial grown as a cool-season annual. It grows 18 to 36 inches tall and has broad, thick leaves and a thick main stalk. Broccoli forms single or multiple flowers “heads ” of tiny blue-green flower buds. The flowers heads are eaten before they bloom; buds open to tiny yellow flowers. Broccoli will bolt and go to seed in warm temperatures or when daylight hours lengthen.
Yield. Plant 2 to 4 broccoli plants for each household member.
Site. Broccoli grows best in compost-rich, well-drained soil with a soil pH between 6.0 and 6.8. Broccoli grows best where air temperatures range between 45° and 75°F. Broccoli is frost hardy and can tolerate temperatures as low as 20°F. In regions where there is heavy rain or sandy soil, aged-compost should be added to the soil to supplement soil nitrogen.
Planting time. Broccoli is a cool-weather crop that must come to harvest before temperatures rise consistently above 75°F. Start broccoli seed indoors 5 to 6 weeks before the last frost in spring. Transplant broccoli seedlings to the garden 2 to 3 weeks before the last frost in spring after hardening seedlings off for 4 days. In mild-winter regions, start seeds indoors in late summer and set them in the garden in autumn for winter harvest. Weather that is too cold or too warm will cause broccoli to go to seed without forming a head. In cold-winter, short-season regions start broccoli in summer for fall harvest.
Planting and spacing. Plant transplants that are 4 to 6 weeks old with four or five true leaves. Leggy transplants or transplants with crooked stems can be planted up to their first leaves so that they will not grow top heavy. Plant seedlings 18 to 24 inches apart in rows 24 to 36 inches apart. Plant seeds and transplants at the same time for succession crops or plant early and midseason varieties at the same time. Sow seed ½ inch deep and 3 inches apart. Transplant thinned seedlings to another part of the garden.
Water and feeding. Keep soil moist during the growing season. Decrease watering when plants approach maturity. Water broccoli at the base of the plant. Side dress plants with well-aged compost at planting time and again at midseason,
Companion plants. Beets, celery, herbs, onions, potatoes. Avoid planting broccoli near pole beans, strawberries, or tomatoes.
Care. Keep broccoli planting beds weed free.
Container growing. A single broccoli will grow in an 8-inch container. Grow multiple plants in larger containers set 18 inches apart. Broccoli is very sensitive to heat so be sure to move plants into the shade on hot days.
Pests. Broccoli can be attacked by cutworms, cabbage loopers (preceded by small yellow and white moths), and imported cabbage worms. Control these pests by hand picking them off of plants or by spraying with bacillus thuringiensis.
Diseases. Broccoli is susceptible to the cabbage family diseases yellows, clubroot, and downy mildew. Plant disease-resistant varieties, rotate crops each year, and keep the garden free of debris to cut back the incidence of disease. Remove and destroy infected plants immediately.
Harvest. Broccoli grown from seed will come to harvest in 100 to 150 days. Grown from transplants broccoli will come to harvest in 55 to 80 days. Cut buds when they are still green and tight. Cut the central head with five to six inches of stem. Leave the base of the plant and some outer leaves to encourage new heads on secondary shoots. Heads that have begun to open showing small yellow flowers are past the eating stage.
Varieties. Aracdia, Bonanza (55 days), Citation, DeCicco, Early Dividend, Emperor (80 days), Eureka (87 days), Green Comet (78 days), Green Goliath (75 days), Green Jewel, Green Valiant (70 days), Italian Sprouting (80 days), Land Mark, Legend (86 days), Love Me Tender, Marathon, Minaret, Packman (80 days), Paragon (75 days), Pinnacle Premium Crop (58 days), Late Purple Sprouting (220 days), Raab Spring, Rapine (70 days), Romanesco (70 days), Saga (57 days), Salad, ShoGun (93 days), Small Miracle, Sprinter, Super Blend, Super Dome, Thompson, Violet Queen (70 days), Waltham (95 days).
Storing and preserving. Broccoli will keep in the refrigerator up to one week or frozen after blanching for up to 3 months.
Common name. Broccoli, Italian broccoli, Calabrese, brocks.
Botanical name. Brassica oleracea italica