Stephen Albert
Sowing: Sow turnips in early spring 4-6 weeks before the last expected frost for a summer harvest. (Sow every 3 weeks until midsummer for a succession of harvests.) Sow 6-8 weeks before the first expected frost in autumn for an autumn and winter harvest. Sow seeds ½” (13 mm) deep. Seeds will germinate in 3-10 days in an optimum soil temperature of 60°F (16°C). Space plants 2-6” (5-15 cm) apart for roots; 1-4” (2.5-10 cm) apart for greens.
Growing: Grow turnips in loose, compost-rich soil free of stones. Keep the soil evenly moist for fast growth; roots will be milder flavored if soil is kept moist. Floating row covers installed on the day of sowing will keep turnips free of insect pests. Mulch with loose straw to protect roots from sunburn in summer. Bone meal or other phosphorus fertilizer will improve yield; feed with an organic fertilizer when plants are 5-6” (13-15 cm) high.
Harvesting: Turnips will be ready for harvest 30 days after sowing—full size in 40 days. Roots are smoothest when small. Harvest can begin when greens are 12” (30 cm) long and roots are 2-3” (5-7.5 cm) in diameter. For greens, harvest the outside leaves, leaving the central growth bud to re-sprout. Do not leave turnips in the ground past maturity; this will cause turnips to become woody and lose flavor. Turnips will keep in the refrigerator for 7-10 days in perforated bags. Greens can be wrapped in damp towel, then placed in a plastic bag, and kept in the refrigerator for a few days.
Read more detailed turnip growing articles at Turnip.
Anyone else has little worms tunnelling into their turnips? What can be done?
Turnip roots riddled with tunnels are the result of burrowing cabbage maggots. The maggots come from very small maggot flies that lay masses of eggs in cracks in the soil near the plants. When the eggs hatch, the white maggots–very small–tunnel down into the roots where they feed or a month or so. You can use row covers to exclude the flies in the future or plant very early in the season before the flies are active. You can use old carpet or tar paper to fashion rings to place around plants to act as a barrier–keeping flies from laying eggs close to plants (a lot of work). You can dust the soil with hot pepper dust to repel the flies.