Growing guidelines: Thin to 1 inch apart when the tops are 2 inches high, and be thorough, because crowded carrots will produce crooked roots. Thin again 2 weeks later to 3 to 4 inches apart.
As the seedlings develop, gradually apply mulch to maintain an even moisture level and reduce weed problems. It’s best never to let young carrot plants dry out. However, if the soil dries out completely between waterings, gradually remoisten the bed over a period of days; a sudden drenching may cause the roots to split. Carrots’ feeder roots are easily damaged, so hand pull any weeds that push through the mulch, or cut them off just below the soil surface. Cover carrot crowns, which push up through the soil as they mature, with mulch or soil to prevent them from becoming green and bitter.