Cool‐weather brassicas are the stars of the spring and autumn garden. In this article, we’ll talk about how to grow broccoli, Brussels sprouts, cabbage and cauliflower.
Brassicas are heavy feeders and like well‐drained soil rich in organic matter. Soil pH should be 6.0 to 7.5, but 6.5 to 7.0 is best. To prepare soil for planting, add two inches (5 cm) of compost and work it in. Add lime, if necessary. Autumn plantings of brassicas are good to follow an earlier planting of peas or beans.
Broccoli, Brussels sprouts and cabbage can be direct seeded in the garden when temperatures are as low as 40°F (4°C), but temperatures of 45°‐85°F (7°‐29°C) are preferable for germination.
Direct seed broccoli outdoors four to six weeks before last frost. Sow seeds 1/2 to 3/4 inch (13‐19 mm) deep three inches (8 cm) apart with two feet (60 cm) between rows. Thin to stand 18 inches (45 cm) apart. The ideal daytime temperature for growing broccoli is in the 60s°F (15°‐21°C).
To grow from transplants, sow a flat of seeds indoors six to eight weeks before last frost. When seeds are one inch (25 mm) tall, plant them in individual pots or six‐packs. Soil should be kept at about 75°F (24°C) until germination, then keep plants at about 60°F (15.5°C). Harden off and plant in the garden when transplants are four to six weeks old, spacing as above.
Broccoli varieties include early ‘Green Comet’ (40 days), ‘Green Goliath’ (53 days), ‘Waltham’ (60‐90 days) and ‘Calabrese’ (60‐90 days).
Brussels sprouts are one of the most cold‐hardy vegetables in the garden ‐ a frost actually improves their flavour. Direct seed Brussels sprouts four months before the first expected autumn frost. Sow seeds three to four inches (8‐10 cm) apart, 1/4‐1/2 inch (6‐12 mm) deep with 30 inches (51 cm) between rows. Thin to 18 inches (46 cm) apart.
To start Brussels sprouts indoors, sow seeds thinly 1/4 to ½ an inch (6‐ 12 mm) deep. Thin to two inches (5 cm) apart. Harden off and transplant when plants are six weeks old, spaced as above.
Brussels sprouts may be green or red. Varieties include early ‘Tasty Nuggets’ (78 days), ‘Long Island Improved’ (80‐115 days) and ‘Falstaff’ (red, 98 days).
Cabbages may be early, midseason, or late‐season. Early varieties are often “pointy”, while later season cabbages are round. Earlies don’t tend to store well. Late season varieties are best for storage or making sauerkraut. Cabbages may be either green or red.
Sow cabbage seeds outdoors as soon as soil can be worked. The ideal daytime temperature for growing cabbage is in the 60s°F (15°‐21°C). Plant cabbage seeds 1/4 to 1/2 an inch (6‐12 mm) deep and three inches (8 cm) apart. Thin to 12 inches (30 cm) apart for small heads and 18 inches (46 cm) for large heads.
Water well as heads are growing, but don’t over water when heads near maturity, as they may split. Direct seed in summer about 99 days from first frost for an autumn crop.
Cabbage varieties include:
- ‘Fast Ball’ (early‐season, 45 days)
- ‘Early Jersey Wakefield’ (early‐season, 65 days)
- ‘January King’ (late‐season, 100‐120 days)
- ‘Red Drumhead’ (late‐season, 90‐100 days).
Of all the cool crops, cauliflower is the hardest to grow. It doesn’t like weather that’s too hot or too dry. The optimal temperature for growing cauliflower is 65°‐80°F (18°‐27°C).
Cauliflower likes the richest soil of any of the brassicas, so work in at least two inches (5 cm) of compost.
Spring cauliflower is best grown from transplants started indoors four to six weeks before last frost. Soil should be kept at about 75°‐80°F (24°‐27°C) until germination, then keep plants at about 60°F (15.5°C). After hardening off, when plants are four to six weeks old, transplant them into the garden. Space plants 15‐24 inches (38‐60 cm) apart with 24‐36 inches (60‐90 cm) between rows. Water well early in the season for good head formation.
If direct seeding in the spring, follow instructions for autumn planting.
Autumn crops can be direct seeded twelve weeks before first frost. Sow seeds 1/2 to 3/4 of an inch (12‐19 mm) deep about three inches (8 cm) apart with 2‐3 feet (60‐90 cm) between rows. Thin to stand 18 inches (46 cm) apart.
Some white cauliflowers must be blanched to keep the curd white. Outer leaves are tied over the curd with a string or elastic band when it is about 2‐3 inches (5‐8 cm) in diameter.
Cauliflower, while usually white, may also be purple, orange, or lime green. Coloured varieties do not require blanching.
Varieties of cauliflower include:
- Snow Crown (self‐blanching white, 48‐70 days)
- ‘Violet Queen’ (purple, 54‐80 days)
- ‘Cheddar’ (orange, 58 days)
This year, try red, purple, or orange brassicas for a colourful splash in your vegetable garden!