Brassica oleracea – The earliest maturing variety that yields “bragging size” quantities with good dark green color. Excellent flavor and outstanding side-shoot development after the main head is cut.
Seed outdoors as soon as weather and soil conditions permit. Cover seed lightly with soil, 6 – 7 seeds per 30 cm (1 ft) of row. Average garden soil and a sunny location are ideal. Thin to 30 cm (1 ft) apart when 7 cm (3 in) high. For earlier Broccoli start indoors 2 to 3 weeks in advance of intended date for moving the plants to the garden. Germinates best at 21 C (70 F) in 7 to 10 days. Reduce temperature after germination to 15 C (65 F) and provide additional light to help prevent stretching and to tone up plants before transplanting outside. Several sowings of Broccoli 10 days apart ensure a fresh supply into fall.
The critical period for heat sensitivity in broccoli lasts just 10 days, during which time the growing point of the plant shifts from vegetative growth to flower bud initiation. This shift, not externally visible occurs 10 days before the appearance of a tiny crown in the center of the plant, or about 3–4 weeks after plants are set out. Temperatures above 35°C for more than 4 days during that critical period result in uneven, poorly shaped heads.