Culture: All members of the cabbage family grow best on a rich, moist, well-drained loam of high fertility. Early varieties require a higher soil fertility than mid- or late-season varieties. Since members of the cabbage family are shallow-rooted, irrigation may be necessary to provide adequate moisture. Cabbage needs a steady supply of water and full sun throughout the growing season. Heads may split if a heavy rain follows a long dry spell without irrigation. A thick layer of organic mulch will conserve moisture and reduce the tendency to bolt in hot weather. Tendency to bolt is affected more by root temperature than air temperature.
Early Crops: Use early varieties that will mature before heavy summer heat settles in, and start seed 4–6 weeks before transplanting to the garden. Sow seed ¼ in. deep. Seedlings need a soil temperature of 75°F, and strong, direct light. Soil temperature can be reduced to 60°F once the seeds have germinated. Maintain good air circulation around plants during all growth stages. Harden plants before transplanting starting a month before last frost. When plants have become properly hardened they can stand a temperature as low as 20°F without buttoning up. Space small head varieties 10–12 in. apart, large head varieties 16–18 in. apart.
Late Crops: For fall crops, either transplant to desired spacing when plants have 3 true leaves or direct sow 6–12 seeds/ft at a depth of ¼–½ in. and thin as needed. Maintain adequate soil moisture during germination.
Note: The tendency to bolt is decreased by applying a thick layer of mulch, and by twisting the head slightly to check the plant's growth when the head is fully grown.
Harvest: After harvest, select the strongest side sprout and allow it to develop into a second, smaller head.
Solar Greenhouse Notes: Use early and midseason varieties. Avoid varieties with savoyed leaves.
Diseases: Where fusarium yellows may be a problem in the Mid-Atlantic region, use resistant varieties. A number of other diseases may affect cabbage. To reduce disease problems, maintain good air circulation, practice good sanitation, and follow a 3-year crop rotation.
Insect Pests: Control cabbage worms and loopers with bT, flea beetles with spinosad, cutworms with paper cylinders around seedlings, and aphids with insecticidal soap. Introducing ladybugs helps control aphids in greenhouses, but they may “fly away home” when introduced into gardens.
Note: Days to maturity are from transplanting.
Seed Savers: Cabbage will cross with brussels sprouts, broccoli, cauliflower, collards, kale, and kohlrabi. Isolate by 1/8 mile for home use. For pure seed of small plantings isolate by 1/4 to 1/2 mile.
Packet: 2g (about 625 seeds) sows 70' direct seeded or 350' as transplants.