Imperial (F1) Broccoli Seed

Scientific name

Brassica oleracea var. italica

Soil and water

Broccoli wants fertile, well-drained soil rich in organic matter at pH 6.0–7.5 and steady moisture all season, so irrigate regularly. A few varieties now handle heat better, but broccoli as a rule struggles in hot weather, and spring and fall crops are the most reliable.

Days to maturity

Counted from transplanting. Add about 20 days for direct sowing.

Spring crop

Choose early and midseason varieties. Sow 1/4" deep: 2 seeds per cell in 72-cell trays, 3–4 seeds per inch in open flats, or in an outdoor seedbed. Keep the soil at 75–80°F (24–27°C) until the seed sprouts if you can, then grow on at about 60°F (16°C) with good light and airflow. Plant out at 3–4 weeks, 10–18" apart in rows 18–36" apart. Broccoli grows best at 55–75°F (13–24°C), ideally 60–70°F (16–21°C), though it still crops in warmer summers.

Fall crop

Choose midseason and storage varieties. Start seedlings the same way in May and plant out in June or July; where hard freezes come early in fall, sow on the early side so heads finish in time.

Winter crop

Where winters are mild and rarely fall below 32°F (0°C), plants can go out from September through February.

Direct sowing

Sow 3 seeds per foot, 1/2" deep, in rows 18–36" apart, and thin each group to one plant.

Seeding rate

At 3 seeds per foot: about 1,000 seeds per 333 ft. Spaced 7" apart in rows 18" apart: about 49,800 seeds (roughly 8.3 oz.) per acre.

Insect pests

Floating row cover from planting day keeps flea beetles and root maggots off young plants; pyrethrin or azadirachtin can be used if flea beetles build up. Bt (Bacillus thuringiensis) controls cabbage worms and loopers. Working the soil 2–4 weeks before planting, to turn under cover crops and weeds, reduces cutworms.

Disease prevention

Prevention works best: long rotations away from brassicas, clean seed-starting mix and seedbeds, and strict sanitation of tools and fields.

Harvest

Cut the central head while the buds are still tight and cool it quickly in ice or cold water. Keep picking side shoots so the plants keep producing.

Storage

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

Sized seed

Broccoli seed is graded to a similar size for precise spacing and even emergence, unless the description says otherwise.

Plant population

At 8" apart in rows 18" apart (1 sq. ft. per plant): about 43,560 plants per acre.

Transplants

Plan on about 850 plants per 1,000 seeds.

Seeds per lb.

About 104,100 on average (range 52,900–142,100).

Packet

100 seeds.

Seeds per lb.

About 79,600 on average.