Growing turnip in zone 7b

Spring planting targets 4 to 6 weeks before the average last frost, which falls around April 1 to April 15 across most of zone 7b's piedmont and mid-Atlantic portions. That puts direct-sow dates in mid- to late March. Fast-maturing varieties like Hakurei reach harvest in 35 to 38 days, allowing spring crops to finish before consistent heat arrives in late May.

Fall planting is the more reliable window. Count back 8 to 10 weeks from the average first fall frost, which typically occurs between October 25 and November 10 in zone 7b. Late August through mid-September sowing gives roots time to size up during October's cooling temperatures. Seven Top, grown primarily for greens, can be seeded a week or two later than root varieties since leaf production tolerates slightly warmer soil at germination.

Clubroot is the primary disease concern for brassicas in zone 7b. The pathogen (Plasmodiophora brassicae) persists in soil for 15 to 20 years, making rotation the most reliable control: avoid planting turnips or any other brassica in the same bed more than once every three to four years. Raising soil pH to 7.2 or above with agricultural lime reduces clubroot severity, though it does not eliminate established infestations.

Flea beetle pressure runs heavier in spring than fall; row covers over newly seeded beds limit feeding damage on cotyledons and young leaves. Brown marmorated stink bug, a notable zone 7b pest, occasionally feeds on brassica tissue but is rarely a primary concern for turnips specifically. Late summer disease pressure from downy mildew can affect fall-planted beds; spacing rows at 12 to 15 inches and avoiding overhead irrigation in the evening reduces leaf wetness and slows spread.