In the northern US, they plant brassica's late July Early, early August. Down here to get excellent growth on both leaves and bulbs, Early September and pray for rain. BTW, most people don't know this, but brassica's are not supposed to be planted in the same field more than 2 years in a row, due to disease issue's. I think they're mostly talking about pure stands. It's beast to plant straight brassica's on one end of a field and on the other end plant your clover and cereal grains. That way you can plant your brassica's sooner and fertilize them with nitrogen. Next year rotate the brassica's to the opposite end. There's some stuff you sew to kill army worms.