Turnips are a versatile crop, providing both tender greens and a globe-shaped root, making them a dual-purpose vegetable. Successfully growing turnips hinges on precise planting techniques, as the tiny seeds are highly sensitive to their initial environment. The depth of the seed, the timing of sowing, and the management of emerging seedlings all determine the final harvest quality.
Understanding Optimal Planting Timing
Turnips thrive in cool weather and have two distinct planting seasons. For an early harvest of greens and smaller roots, sow seeds in early spring, typically two to three weeks before the final expected frost date. This timing allows the plants to mature before the intense heat of summer arrives. If temperatures climb above 75°F, the plant may prematurely flower and produce a seed stalk, a process called bolting.
The most successful planting window for developing large, sweet roots is late summer or early fall. Sowing seeds in August or September ensures root development coincides with naturally cooling soil and air temperatures. The roots of a fall crop become sweeter and more tender after a few light frosts, which converts starches into sugars. This second planting avoids the heat stress that often causes spring-planted turnips to become woody or develop a bitter flavor.
The Critical Planting Depth
The most direct answer to a successful turnip crop is to plant the seeds at a depth of approximately 1/2 inch. This shallow depth is important because turnip seeds are small and contain a limited amount of stored energy (endosperm) to fuel initial growth. Planting them any deeper than 1/2 inch means the developing seedling must expend too much of its finite energy reserve pushing the sprout through a greater layer of soil. If the seed is buried too deeply, it may exhaust its resources before reaching the soil surface and beginning photosynthesis, resulting in failed germination.
Conversely, planting the seed too close to the surface, such as less than 1/4 inch deep, poses the risk of desiccation. Tiny seeds require consistent moisture for the germination process to initiate and sustain the young sprout. A shallowly placed seed is vulnerable to drying out quickly from sun and wind exposure, which halts germination and kills the fragile embryo. The 1/2 inch depth offers the ideal compromise, providing enough insulation and consistent moisture while still being shallow enough for the seedling to emerge efficiently.
Essential Soil Preparation and Seed Spacing
Turnips grow best in loose, well-draining soil that is rich in organic matter, which facilitates the downward expansion of the root. Heavy, compacted, or clay-rich soil can physically impede development, causing the roots to be small, forked, or misshapen. Before sowing, the soil should be loosened to a depth of 12 to 15 inches, and any large stones or clods should be removed. A soil pH between 6.0 and 6.5 is preferred for optimal nutrient uptake.
When initially sowing, the tiny seeds should be distributed thinly, aiming for a spacing of about 2 to 3 inches between seeds. Sowing them in specific rows helps with organization and maintenance later on. This initial spacing prevents competition among the young sprouts, which can weaken the developing seedlings. Creating a fine, crumbly seedbed is important, as a cloddy surface will reduce seed-to-soil contact, leading to poor and uneven germination.
Managing Post-Germination Thinning
Once the turnip seedlings have successfully emerged and grown to about 2 inches tall, developing their first set of true leaves, thinning becomes mandatory. This step is necessary because even the thinnest initial sowing often results in overcrowding, which will severely limit the size of the final root crop. Overcrowding forces plants to compete intensely for light, water, and soil nutrients. If left un-thinned, the plants will produce an abundance of greens but only small, crowded, and often woody roots.
To promote the development of large, desirable roots, thin the seedlings so the remaining plants are spaced 4 to 6 inches apart. For varieties grown primarily for greens, a closer final spacing of 2 to 3 inches is acceptable. Remove the weaker or smaller seedlings by gently snipping them at the soil line with scissors to avoid disturbing the roots of the plants you intend to keep. Watering the area lightly after thinning helps the remaining plants recover quickly from the minor disturbance and encourages robust root growth.