key growing information

How to Grow Broccoli From Seed

How to grow heading broccoli from seed: spring, fall and winter planting schedules, transplant care, spacing, pest and disease prevention, harvest and storage.

By Hensley’s Seed Co. September 3, 2026

Standard Heading Broccoli Key Growing Information

A head of standard broccoli, growing in the field.

SCIENTIFIC NAME:

Brassica oleracea

CULTURE:

Broccoli wants fertile, well-drained soil rich in organic matter, with a pH of 6.0–7.5. Even moisture through the season matters, so water regularly. Some newer varieties handle heat better, but broccoli generally struggles in hot weather; spring and fall crops are the most dependable.

DAYS TO MATURITY:

Counted from transplanting; allow about 20 more days when direct sowing.

EARLY SPRING CROP:

Choose early and midseason varieties. Sow ¼" deep, 2 seeds per cell in 72-cell plug flats, 3–4 seeds per inch in 20-row flats, or in an outdoor seedbed. Transplants are usually ready in 3–4 weeks. If you can, hold the soil at 75–80°F (24–27°C) until seedlings emerge, then drop the air temperature to around 60°F (16°C) and give plenty of light and airflow. Set plants 10–18" apart in rows 18–36" apart. Broccoli grows best between 55 and 75°F (13–24°C), ideally 60–70°F (16–21°C), though it can still produce well in warmer summer weather.

FALL CROP:

Grow midseason and storage varieties. Start seedlings the same way in May and plant them out in June or July. Where hard freezes come early in fall, sow early enough that heads have time to mature.

WINTER CROP:

In mild-winter areas where temperatures seldom drop below 32°F (0°C), broccoli can be grown through winter, with transplants set out anytime from September through February.

DIRECT SEEDING:

Plant ½" deep in groups of 3 seeds every foot, rows 18–36" apart, and thin each group to the strongest seedling.

AVG. DIRECT SEEDING RATE:

At 3 seeds per foot, 1,000 seeds sow about 333'. For an acre at 7" in-row spacing and 18" between rows, plan on about 49,800 seeds (roughly 8.3 oz.).

INSECT PESTS:

Covering young plants with floating row covers right after planting keeps flea beetles and root maggots away. If flea beetle pressure gets heavy, use insecticides such as pyrethrin or azadirachtin. Bacillus thuringiensis (Bt) controls cabbage worms and loopers. To head off cutworms, till the soil 2–4 weeks before planting to incorporate cover crops and kill weeds.

DISEASES:

Prevention is the best approach: (1) rotate with non-brassica crops for several years, (2) use clean seed-starting mix and seedbeds, and (3) keep tools and fields clean. Select broccoli seed lots that tested negative for black rot (Xanthomonas campestris pv. campestris) and black leg (Phoma lingam). Keep in mind that a negative test only means the pathogen wasn't detected in the sample examined; it is not a guarantee the whole lot is disease-free, and no seed treatment can promise that either. Feel free to contact us with specific questions.

HARVEST:

Cut the central head while the buds are still closed, and chill it with ice or cold water right away. Keep picking the side shoots that follow to extend the harvest.

STORAGE:

Holds 10–14 days at 32°F (0°C) and 95–98% relative humidity with good air movement.

SIZED SEEDS:

Sized seed has been graded to a uniform size, which gives more precise spacing in mechanical seeders and a more even stand. Our broccoli seed is sized unless the product description says otherwise.

TYPICAL PLANT POPULATION:

About 43,560 plants per acre (1 sq. ft. each) at 8" in the row and 18" between rows.

TRANSPLANTS:

About 850 transplants per 1,000 seeds on average.

SEEDS/LB.:

52,900–142,100 (average 104,100).

PACKET:

100 seeds per packet, enough for about 50'.