How to Grow Broccoli From Seed

Broccoli is a cool-season crop that heads up best in mild weather, so most gardeners start it indoors and transplant. For a spring crop, sow seeds indoors 4 to 6 weeks before your last frost, then set the seedlings out 2 to 3 weeks before that last frost, since young plants shrug off light frost. For a fall crop, which is often the sweeter and easier one, start seeds in mid to late summer so the heads mature as the weather cools.

Sow broccoli seeds a quarter inch deep in cell trays or small pots of moist seed-starting mix, two seeds per cell, and keep them around 70 to 75F. Seedlings usually appear in 5 to 10 days; thin to the strongest one per cell. Harden them off for a week, then transplant into rich, firm soil in full sun, spacing plants 18 inches apart in rows 24 to 36 inches apart. You can direct-sow in mild climates, but transplants give more reliable heads.

Broccoli is a hungry, thirsty plant. Give it steady moisture, about 1 to 1.5 inches of water a week, and feed with a nitrogen-rich fertilizer a few weeks after transplanting to push leafy growth. Firm soil and even watering help form tight heads. Watch for cabbage worms and aphids, the usual brassica pests, and pick worms off by hand or cover young plants with row cover. In hot regions like the South or interior California, grow broccoli as a fall and winter crop, since summer heat above the mid-80s makes heads open into loose yellow flowers early; in the North, both a spring and a fall planting work well.

Broccoli grows well beside plants that repel or distract its main pests, the cabbage worm and flea beetle. These four make especially good neighbors in a brassica bed, and you can add any of them in one click:

Cut the central head while the buds are still tight and green, before any yellow flowers show, slicing the stem about 5 to 6 inches below the head. Harvest in the cool of the morning. After you take the main head, leave the plant in the ground and keep watering: most varieties push out smaller side shoots for weeks, giving you a steady second harvest of bite-sized florets.

Eat broccoli raw with dip, or steam it just until bright green and still crisp, roughly 4 to 5 minutes, so it keeps its color and bite. Roasting at high heat gives crisp, browned edges. The tender stalks are good too, peeled and sliced. Homegrown broccoli is sweeter than store-bought, and the leaves and side shoots are all edible, so little goes to waste.

• Buttoning (tiny premature heads): usually from stress, cold shock at transplant, or crowding. Grow strong seedlings, harden off gently, and keep plants fed and watered.
• Bolting or loose heads: heat makes broccoli flower fast. Time the crop for cool weather and favor a fall planting in warm regions.
• Cabbage worms: green caterpillars that chew the leaves and heads. Pick them off, or float row cover over young plants to keep the white moths out.
• Aphids: rinse them off with a strong spray of water and invite in ladybugs and lacewings by planting flowers nearby.