Turnips are a fast-growing, cool-season crop that offers a dual harvest of both the root and the tender greens. These members of the Brassica family are best known for the sweet flavor they develop when grown in the declining temperatures of autumn. Successfully cultivating a fall turnip crop requires precise timing, as the planting window in late summer is narrow. The following guide details the necessary steps for planting and caring for turnips to ensure a flavorful autumn yield.
Calculating the Optimal Planting Date
Determining the precise sowing date for a fall harvest relies on two factors: the Days to Maturity (DTM) of the specific turnip variety and the average first expected frost date for your region. Turnip varieties vary significantly, maturing in 35 to 80 days. Knowing your chosen variety’s DTM is important before calculating the planting window.
The formula begins by counting backward from your area’s average first frost date by the number of days required for the turnip to mature. For example, if your average frost date is October 25th and the DTM is 50 days, the target maturity date is September 5th. This calculation must incorporate a buffer period to account for the slower growth that occurs as days shorten and temperatures cool in early autumn.
A buffer of 10 to 14 days should be added to the total DTM before subtracting from the frost date. This adjustment compensates for the reduced light intensity and cooler soil temperatures of late summer and early fall, which slow the plant’s growth rate. Therefore, a 50-day turnip variety needs 60 to 64 days of growth to reach optimal size before cold weather sets in. This adjusted window allows roots to develop properly while benefiting from the flavor-enhancing effects of light frost.
Preparing the Soil and Seedbed
Successful turnip root development depends on proper soil preparation before planting. Turnips thrive in loose, well-draining soil that allows the root to expand without obstruction. The planting bed should be tilled or loosened to a depth of eight to twelve inches. Removing any rocks or large debris is important, as these can cause the developing root to become forked or malformed.
Turnips prefer a slightly acidic to neutral soil pH, ideally ranging from 6.0 to 7.5. Incorporating aged compost or well-rotted manure before planting will improve drainage and provide nutrients, though excessively rich soil is not required. Avoid fertilizers high in nitrogen, which encourages leaf growth over root development. The planting site should receive a minimum of six hours of direct sunlight daily.
Essential Care for Summer-Planted Turnips
The primary challenge for late-summer planted turnips is managing high summer temperatures, which can cause roots to become woody or bitter. Consistent soil moisture is required, especially during germination and early growth, to prevent drought stress. Provide at least one inch of water per week, ensuring it soaks deeply into the soil.
Thinning the seedlings is necessary once the plants have developed their first set of true leaves, typically when they are a few inches tall. For the largest root development, plants must be spaced 4 to 6 inches apart, as crowding leads to stunted roots. If the primary goal is to harvest the greens, a closer spacing of 2 to 4 inches can be maintained, since root size is a secondary concern.
Gardeners should monitor for common late-summer pests, such as flea beetles and aphids. Flea beetles chew small holes in the leaves of young seedlings, which can impede growth. Using a lightweight floating row cover immediately after planting is an effective, non-chemical method to block these insects from reaching the vulnerable young plants.
Knowing When to Harvest Turnips
Turnip roots are typically harvested when they reach a diameter of 2 to 4 inches, depending on the variety and desired tenderness. Harvesting them early results in a milder, sweeter flavor and a more tender texture. Waiting too long causes the roots to become overly large, often leading to a pithy or woody interior and a stronger flavor.
The greens can be harvested when they are young and tender, beginning when the leaves are about 6 inches long. To ensure continued root growth, only the outer leaves should be selectively picked, leaving the central leaves intact to support the plant’s photosynthesis. The sweetest flavor in the root is achieved after the plant experiences a few light frosts, which triggers the conversion of starches into sugars within the root.
The entire crop should be harvested before a hard freeze occurs (temperatures consistently below 25°F). To harvest the root, grasp the foliage near the base and pull upward, or use a garden fork to gently loosen the soil before pulling it out. Once harvested, the greens should be cut from the roots to prevent moisture loss and maintain crispness.