Culture: Culture of broccoli is similar to cabbage, but broccoli is more sensitive to hot weather. See Cabbage section for detailed cultural notes. Start seeds indoors 4-5 weeks before transplanting out. Transplants should have at least 4 leaves. Transplant starting 1 month before last spring frost. (If seedlings experience 20 degrees F or lower they may "button up" and only make tiny heads, because the plants will think that they've gone through a winter and that it's time to flower.) Broccoli does best in cooler weather - avoid maturing heads in deep summer heat. For fall crops start seed 10-12 weeks before the first hard freeze date, and transplant to garden after seedlings are well developed. Broccoli requires a steady supply of moisture in a well-drained fertile soil. Any temporary arrest of growth will adversely affect production and taste. Keep a deep layer of mulch on the soil during hot weather. Side-sprouting varieties have smaller central heads with many side sprouts, a feature that is useful for extended harvest. Plant in raised beds or rows 12-16 in. apart.
Broccoli Raab: A spicier relative of broccoli, used in Italian cooking, quicker to mature. Best planted in spring and for fall. Space closer than regular broccoli, 4-6 in. apart. For multiple harvests, just as the flower buds are starting to open, use knife or hand pruners to harvest the buds and several leaves below them.
Maturity Dates: Days to maturity are from transplanting. Add 25 days if from seed.
Seed Savers: Broccoli will cross with brussels sprouts, cabbage, cauliflower, collards, and kohlrabi, and most kale. Broccoli Raab will cross with Chinese cabbage, turnips, and some rapeseed (canola).Isolate by 1/8 mile for home use. For pure seed of small plantings isolate by 1/4 to 1/2 mile.
Packet: Open-pollinated varieties, 2 g (about 625 seeds) unless otherwise noted, sows 50' direct seeded or 350' as transplants.