Planting fall turnips at the right time is the single most important factor for a successful harvest. While these hardy vegetables are resilient, getting the schedule wrong can result in small, woody roots or plants that are killed by early frost. The key is to align the growing period with the cooling temperatures of late summer and autumn, ensuring the turnips develop flavor and size before the ground freezes.
Understanding the Frost Calendar
To determine when to plant, you must first look at the calendar in relation to your local climate. Turnips thrive in cool weather and actually improve in flavor after a light frost, as the sugars concentrate to protect the plant. However, they cannot survive a hard freeze that damages the crown. Therefore, the primary guideline is to calculate backward from your average first fall frost date, which is typically provided on seed packets or by local agricultural extensions.
Calculating Your Planting Window
The general rule of thumb is to sow seeds approximately 6 to 8 weeks before the first expected frost. Turnips are quick growers, with most varieties reaching maturity in 35 to 60 days. If you live in a region with a long autumn, you can stretch this window to 8 weeks. Conversely, if you are in a warmer climate where frost arrives late, you can narrow it to 6 weeks. The goal is to have the roots fully formed and ready to harvest before temperatures consistently drop below 20°F (-6°C).
Regional Variations and Timing
Because of the vast differences in climate across North America, the specific date varies significantly by region. In the northern United States and southern Canada, where frost occurs early, planting usually happens in mid to late summer. In the southern states, where winters are mild, turnips can often be planted in late summer for a harvest that extends into winter or even early spring.
Late Summer in the North
For gardeners in USDA zones 3 through 6, the optimal sowing period is usually between mid-July and mid-August. Planting in July ensures that the roots are large enough to store energy before the cold sets in. If you plant too late, the turnips may not size up adequately, resulting in a smaller yield that might not survive the winter months outdoors.
Fall and Winter in the South
Conversely, gardeners in zones 9 and 10 should look at planting dates in September, October, or even November. In these regions, the challenge is not the cold but the heat of mid-summer. Planting in late summer often means dealing with germination issues due to hot soil. Waiting for the temperatures to drop ensures better seed viability and stronger initial growth. Some varieties specifically labeled as "winter turnips" are ideal for these climates, as they tolerate milder conditions and continue to grow slowly throughout the cooler months.
Soil and Succession Planting
While the calendar is a guide, the condition of the soil is equally important. Turnips prefer loose, well-draining soil with a pH between 6.0 and 6.8. If your soil is compacted, the roots will become misshapen and stunted. To maximize your harvest, consider succession planting. Sowing a new batch of seeds every 7 to 10 days ensures a continuous supply of turnips rather than a single large harvest, allowing you to enjoy young, tender roots and mature storage crops throughout the season.
Signs It Is Too Late
Even if you have missed the optimal planting window, it is not always too late to plant a crop. However, you must adjust your expectations. If the turnips are still small when the first hard frost hits, they will likely not survive if left in the ground. In this scenario, you can harvest any decent-sized roots before the freeze and use them immediately in cooked dishes. Alternatively, you can pull the plants and store them in a cool, humid location, though the quality may decline rapidly compared to properly timed crops.
