Broccoli has rocketed up the vegetable popularity charts in recent years, thanks in large part to medical researchers, who have shown in study after study that broccoli and other members of the Brassica family produce a cancer-fighting substance called sulforaphane. Broccoli is a cool-season vegetable that prefers its temperatures on the mild side.
- You can grow broccoli anywhere in USDA Zone 3 or above, but your crop will be most productive where nights are cool and daytime temperatures hover in the upper 60s F.
- Choose a site that has good drainage and air circulation, gets full sun or light shade, and where broccoli, cauliflower or other members of the Brassica genus have not grown for at least four years. And, because broccoli grows about three feet tall, choose a site where the plants won't shade other crops.
- Plant broccoli in soil to which you've added plenty of compost or well-rotted manure. The plants perform best in soil with a neutral pH of 7.0, but they'll do fine with anything between 6.2 and 7.2.
- Sow broccoli seeds directly into the garden a month or two before the last frost in cool climates or in early spring in warmer regions.
- Get a jump on the growing season by starting seeds indoors six to eight weeks before the last frost. Put hardened-off seedlings into the ground about two weeks before the last frost, setting them into the soil up to their first true leaves and about 18 inches apart.
- Add a topdressing of compost or well-rotted manure when the central head is about an inch across to give the new plants a nutritional boost.
- Keep the soil moist. If rainfall is scant, give the plants one to two inches of water each week.
- Mulch to retain moisture and deter weeds, and cover the plants with floating row covers to protect them from the cold and discourage insect marauders. A paper collar around each plant, at soil level, will help foil cutworms.
- Start picking broccoli as soon as the heads are big enough to use. Be sure to harvest all the flower stalks before you see any sign of yellow: it means the tiny buds are beginning to open.
Broccoli can fall victim to clubroot, a fungus that can invade your garden on infected plants. You can avoid the disease by growing your own seedlings rather than buying them, by growing broccoli and other Brassica crops in a different spot each year, or by choosing disease-resistant cultivars. (They'll be marked as such in seed catalogs.)