The timing for planting turnips (Brassica rapa) in USDA Hardiness Zone 7 is determined by the plant’s preference for cool weather. This fast-growing, cool-season crop thrives in temperatures between 40°F and 75°F. The planting schedule is dictated by the spring and fall frost dates. Turnips are highly sensitive to prolonged heat, which causes the roots to become woody and bitter, so timing the harvest before or after the summer peak is essential.
Spring Planting Window
Spring planting in Zone 7 is timed around the average last frost date, which typically falls between March 22 and April 3. For a spring harvest, direct-sow seeds approximately four to six weeks before this date. This timing allows the plants to mature before summer temperatures arrive.
While this window is ideal for a quick harvest of tender turnip greens, the roots often struggle to develop fully. The rapid onset of warmer weather can cause the plant to bolt, or prematurely flower, ending desirable root growth. If an unexpected late frost is predicted, covering the young seedlings with a row cover or mulch will offer adequate protection. Spring-planted turnips should be harvested relatively small, generally within 35 to 50 days, to avoid the woody texture and strong flavor induced by heat.
Fall Planting Window
The fall planting window is preferred for producing the sweetest and most tender turnip roots in Zone 7. This timing utilizes cooling temperatures, which concentrates sugars within the root tissue. To calculate the ideal seeding time, count backward from the average first frost date, which usually occurs between October 29 and November 15.
Since most common turnip varieties mature in 40 to 60 days, aim to sow seeds 60 to 75 days before the first expected frost. This places the optimal seeding period from mid-July through mid-August. Planting within this window ensures the roots swell and sweeten during the cooler temperatures of early autumn.
Sowing seeds in the high heat of mid-summer requires careful attention to consistent moisture for germination and early growth. Starting the seeds in late summer allows the plants to establish strong root systems before the cooler, shorter days of fall arrive. The decreasing daylight and soil temperatures of September and October promote the desired mild flavor and firm texture of the root.
Essential Growing Requirements
Successful turnip production relies heavily on proper soil preparation and specific nutrient management. Turnips require a loamy, loose, and well-drained soil structure that has been deeply tilled to a depth of at least 12 inches. The loose soil is necessary to allow the root to expand without resistance, and a soil pH between 6.0 and 6.5 is ideal for this brassica crop.
The necessity of low-nitrogen fertilization is a specific detail of turnip cultivation. High-nitrogen fertilizers should be avoided because they promote excessive leafy growth at the expense of root development. A balanced, low-number fertilizer, such as a 5-5-5 formula, worked into the soil before planting provides the necessary phosphorus and potassium for healthy root formation.
Seeds should be direct-sown into the garden bed at a shallow depth of one-quarter to one-half inch. Once the seedlings emerge and reach a height of a few inches, thinning is a non-negotiable step to ensure proper root sizing. Seedlings must be thinned to leave four to six inches between each plant; crowding will result in small or underdeveloped roots. Maintaining consistent soil moisture is necessary throughout the growing period, as fluctuating water levels can cause the roots to develop a tough, woody texture.