Broccoli, Brussels Sprouts, Cauliflower and Kohlrabi - 2010 Ohio Vegetable Production Guide
These are cool-season crops, with the harvest period generally in the spring and fall.
A spring crop in Ohio generally is not possible due to too-cool temperatures, which can cause premature heading, or buttoning. The temperature range causing this condition averages 50-60°F for a period of 10-14 days and only affects plants that are past the juvenile stage. Postjuvenile plants are considered to be those exceeding 3-4 true leaves, depending on variety.
Transplants are grown 4-6 weeks before planting in the field. One ounce of cauliflower seed will provide 3,000 transplants. Field seeding begins in April and ends in mid-July. Field seeding on heavy soils requires continuous moist conditions to ensure proper emergence. Allow 15-20 days ahead of transplanting to achieve equal maturity.