Turnips are a versatile, dual-purpose crop, valued for both their nutritious greens and crisp, sweet roots. Successfully cultivating turnips in Oklahoma requires precise timing, as this hardy, cool-season vegetable thrives when temperatures are between 40°F and 75°F. Planting must be strategically scheduled to ensure the plant matures during the cooler periods of the year, avoiding mid-summer stress that can ruin the root’s flavor and texture.
Timing the Primary Fall Planting
The most reliable and flavorful turnip harvest is achieved by planting in the late summer for a fall and winter crop. This primary planting window should begin in mid-August and continue through mid-September. This timing allows 6 to 10 weeks of growth before the average first significant frost arrives.
Planting during this period ensures that developing roots mature as soil temperatures decrease. A light fall frost improves the sweetness of the roots by concentrating natural sugars. For a continuous harvest, gardeners can sow successive batches of seeds every two weeks until about October 1st. However, planting later than mid-September risks roots not fully forming before a hard freeze stops growth.
Starting seeds while the ground is still warm in late August accelerates initial germination. The subsequent cooling air temperatures of September and October provide the ideal environment for the turnip to transition from leaf production to bulb enlargement.
Considerations for Spring Planting
While fall provides the best conditions for a robust root harvest, spring planting is possible for a quick, early-season yield, particularly of turnip greens. To succeed, direct seeding must occur very early, typically starting in late February or early March. The goal is to complete the entire growth cycle before the arrival of consistently high daytime temperatures, which can begin as early as May.
The main challenge is premature bolting, where the plant shifts energy from root and leaf production to forming a flower stalk and setting seed. Bolting is triggered by rapidly rising temperatures or temperature stress. Once a turnip bolts, the root becomes woody, tough, and develops an undesirable flavor.
Gardeners focused on harvesting greens have a greater chance of success, as greens require less time to mature than the root. Quick-maturing varieties, such as ‘Tokyo Cross’, are better suited for this narrow window. The entire spring crop must be harvested before daily average temperatures consistently exceed 75°F to ensure quality.
Essential Steps for Turnip Success in Oklahoma
Regardless of the planting season, soil quality largely determines the turnip’s success. Turnips require a loose, deeply worked, and well-draining soil structure, ideally with a pH between 6.0 and 7.5. Heavy clay soil must be amended with organic matter to prevent developing roots from becoming misshapen or stunted.
Directly sowing the small seeds requires a step called thinning for proper root formation. Turnip seeds are typically sown densely, but the resulting seedlings must be thinned when they are a few inches tall to stand four to six inches apart. Overcrowding causes plants to compete for resources, resulting in small, underdeveloped roots.
Selecting a suitable variety is also important for Oklahoma gardening. Cultivars such as ‘Purple Top White Globe’ are widely adaptable and reliable for producing both greens and roots. For those prioritizing greens, the ‘Alltop’ variety is specifically bred for foliage production. Focusing on these factors helps mitigate environmental stresses characteristic of the Oklahoma growing environment.