Try to ensure a gap of at least
1.95 feet (60.0 cm) when sowing to prevent overcrowding your seedlings. For optimal germination, soil temperature should be a minimum of
18°C / 64°F.
By our calculations, you should look at sowing Romanesco about 48 days before your last frost date.
Romanesco is half hardy, so ensure you wait until all danger of frost has passed in your area before considering planting outside.