Broccoli (Brassica oleracea var. italica)
Related vegetables: arugula, Brussels sprouts, cabbage (all types), cauliflower, kale, kohlrabi, mustard, radish, rutabaga, turnip, horseradish, collards, watercress
- Cool season annual.
- There are different types of broccoli—annual green or, more rarely, purple “heading” broccoli; “romanesco,” which has yellowish green, conical groups of buds arranged in spirals; and sprouting broccoli, an overwintering annual or perennial, rarely grown in this country. Heading broccoli forms the large, rounded flower heads commonly seen in groceries. Sprouting broccoli forms small shoots in the leaf axils over a long period instead of forming a large head.
- Unopened flower buds, stems, and young, tender leaves can be eaten.
- Medium height, about 3 ft.
- In spring, plant transplants 4-6 weeks before average last frost date. Planting can continue into April, even through May in the coldest part of the state. If growing from seed, start indoors 5-7 weeks earlier. Spacing is 18-24”, rows a minimum of 36” apart, spacing within a wide row is 12”- 18”.
- For a fall harvest, plant transplants about 70 days before the average first frost date. Seeds can be planted outdoors 4-6 weeks earlier. No matter the season, broccoli grows best if it can mature when air temperatures are somewhat warm but not hot (less than 80 °F). Broccoli is very frost tolerant. Mature plants can survive temperatures down to 25 °F, perhaps lower with protection.
- First harvest is about 60 days from transplant and about 110 from seed. Cut off flower head before flowers open plus about 5” of stem. Small side shoots may develop, providing an additional harvest. Estimated yield per 10 ft row is 10 lb.
Broccoli is usually put into the garden as transplants. These can be purchased or you can grow your own from seed. For spring planting, start seeds indoors 5-7 weeks before your anticipated planting date. Temperature optimum for germination is 70-80 °F, for seedling growth is 60-70 °F. Plant seeds 1/4-1/2” deep, seedlings appear in about 5 days.
The first transplants can be put into the soil 4-6 weeks before the average last frost date. Seedlings should have at least 4 pairs of leaves. Smaller seedlings are very sensitive to frost. Planting for fall harvest is done in late summer. If using transplants, assume harvest will be on average first frost date, then count back the number of days from transplant to harvest for your cultivar plus 10 days.
You can grow these transplants from seed also. Since the soil has warmed, you may be able to plant seeds directly into the garden as well as starting them indoors. Plant seeds 4-6 weeks before the anticipated transplanting date. Practice crop rotation. Do not plant the same area with a cole crop two years running.