Swiffy: don’t be concerned with how high your weeds are. They can be 3 feet high and you can give them a good spraying. Come back 4 days later and broadcast your brassica seed and run a Cultipacker over the seed and you will get a good crop assuming your PH is good and fertilizer. Those weeds will die and be brown about 8 days later and will fall over on the soil and act as a good mulch and keep moisture in for your brassicas. Key is tho to get a good kill when you spray with weeds really high. Those weeds will be your friend.