Broccoli

About Broccoli

Broccoli is grown for its tight green heads of flower buds and keeps producing smaller side shoots after the main head is cut. It develops best in cool weather, so it is grown as a spring or fall crop.

Grown as a cool-season annual in every zone; time it for the cool weather of spring or fall. Plants keep growing after the first light fall frosts.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

• Start seeds indoors: 6 to 8 weeks before the last frost
• Set out plants: 2 to 4 weeks before the last frost
• Fall planting: 8 to 10 weeks before the first fall frost

Days count from transplanting: about 50 to 60 for spring varieties and 60 to 85 for fall ones. The fall number is for setting out transplants started in midsummer; plants held too long in pots may form tiny 'button' heads.

Soil

Fertile, well-drained soil that holds moisture; plants must never go short of water as heads form.

Work in compost or well-rotted manure and follow a soil test; without one, about 2.5 lb of balanced fertilizer such as 10-10-10 per 100 sq ft before planting, with soil pH about 5.8 to 6.5.

Feeding

• 3 to 4 weeks after transplanting, once plants are established (direct-seeded plants: when about 6 inches tall): nitrogen fertilizer such as calcium nitrate (15.5-0-0) or 21-0-0. Use about 2 lb of calcium nitrate per 100 ft of row, or 1/2 cup of 21-0-0 per 10 ft of row, beside the plants and water it in.
• when the main head is about the size of a quarter: nitrogen fertilizer such as 21-0-0. Add about 1/4 cup per 10 ft of row beside the plants and water it in.
• after cutting the main head: nitrogen fertilizer such as 21-0-0. A little more nitrogen helps the side shoots grow; water it in.

Do not use fresh manure or weed-and-feed products, and skip extra phosphorus unless a soil test calls for it.

Harvest

Cut the central head, with 5 to 6 inches of stem, while the buds are still tight and before any yellow flowers open. Keep picking the side shoots that follow.

After you cut the main head, many smaller side shoots form; keep cutting them as they reach usable size.

Varieties (32)

Good neighbors

Thyme, Onion, Nasturtium, Radish

An Iowa study cited by UMN Extension found thyme, onion and nasturtium helped reduce cabbage looper damage on broccoli; radishes at the base are a space-saver.

Pests to watch for

Imported cabbageworm, Cabbage looper, Flea beetles, Aphids, Whiteflies, Slugs, Harlequin bug, Swede midge, Bagrada bug, Garden symphylan, Beet armyworm, Cabbage maggot, Diamondback moth, Fungus gnats

Diseases and problems

Black rot, Clubroot, Alternaria leaf spot, Edema (oedema), Transplant shock, Too little light (leggy plants), Bolting (going to seed), Boron deficiency, Nutrient deficiency, Tipburn, Downy mildew, Damping-off, White mold, Sooty mold, Turnip mosaic

In the kitchen

Steamed, roasted, stir-fried or eaten raw; the peeled stems are tender too.

Keeping it: Refrigerate unwashed heads in a loose, open bag and use within 3-5 days; with cold, humid storage it can last about 2 weeks.

Safety: If you take the blood thinner warfarin, keep the amount of vegetables like broccoli about the same from day to day, because they are rich in vitamin K (NIH Office of Dietary Supplements).

Pets: Not listed as toxic by the ASPCA