Turnips are a popular cool-season crop in Alabama, offering nutrient-rich greens and satisfying root vegetables. A successful harvest requires the plants to grow during cool weather, as high temperatures cause roots to become woody and greens to taste bitter. Planting timing must be precise, aligning with seasonal temperature shifts rather than a fixed calendar date.
Defining the Optimal Planting Windows
Turnips thrive when air temperatures are consistently cool, ideally ranging between 40°F and 75°F. This creates two distinct planting windows in Alabama: a short Spring season and a longer Fall season.
For a Spring crop, sow seeds directly into the soil two to three weeks before the average last expected frost date. This early planting allows the crop to mature quickly, typically within 40 to 60 days, before intense summer heat arrives.
The Fall planting window is superior for developing large, sweet turnip roots. To time this, count backward from the area’s first expected frost date, planting seeds eight to ten weeks prior. Optimal soil temperatures for germination (60°F to 70°F) often mean planting from late August through early October in Alabama. Planting during this period ensures roots develop during cooling autumn days, which concentrates natural sugars and improves flavor.
Regional Adjustments for Alabama’s Climate
Alabama’s climate zones, ranging from USDA Hardiness Zone 7a in the north to 9a in the south, significantly affect planting times. Northern Alabama (Zone 7a), including areas near Huntsville, experiences the earliest first frost, typically in mid-to-late October. Gardeners here must begin Fall planting in late August to ensure roots mature before the hard freeze.
Central Alabama, around Birmingham and Montgomery, has a longer growing season, with the first frost generally arriving in early to mid-November. This extends the Fall planting window, allowing sowing to continue through September.
Southern and Coastal Alabama (Zone 9a), including Mobile, are the warmest zones and often do not see frost until late November or early December. This allows for a longer growing period, with Fall planting possible well into October and often enabling a mild winter harvest of greens. Planting dates must be tailored to the specific local microclimate.
Essential Soil Preparation and Seed Requirements
Turnips require loose, well-drained soil that allows the storage root to expand without obstruction. Heavy clay common in Alabama must be amended. Incorporating well-rotted compost or manure improves both drainage in clay and moisture retention in sandy soils.
The ideal soil pH is slightly acidic to neutral (5.5 to 6.8), which should be confirmed with a soil test. Sow seeds directly into the prepared bed at a shallow depth of one-quarter to one-half inch.
After seedlings emerge and reach a few inches in height, they must be thinned to a final spacing of four to six inches apart. This prevents crowding, which results in small or malformed roots. Avoid applying high-nitrogen fertilizers, as this prioritizes leafy greens over root development.
Harvesting Strategies for Greens and Roots
Turnips offer both edible greens and the root vegetable. Greens can be harvested relatively early, often within a month of planting, using a “cut-and-come-again” method. This technique involves removing only the outer, larger leaves, leaving the central growing point intact to produce new foliage. Harvesting greens early provides a continuous supply without significantly hindering root growth.
The roots require the full maturity period, typically 40 to 60 days from seeding. They are best pulled when they reach about two to three inches in diameter; leaving them longer can lead to a woody texture and strong flavor. A light frost in late fall benefits the roots, causing starches to convert to sugars, resulting in a sweeter and milder flavor.