This year I sowed all my carrots early in a tall big tub, mainly to keep them away from the badger; she loves carrots.
I sowed a lot for my use and to give away to non grower friends but found every one I pulled has fly damage. I didn't cover them as I believed the tale about carrot fly only cruising a foot or so above the ground which I now know is false. So, short of covering the carrots next season, are there any tips on growing good healthy carrots?