Purple Top Turnips are a popular cool-season vegetable known for their distinctive white roots crowned with a vibrant purple shoulder. This heirloom variety is prized for its dual harvest, providing both tender, nutritious greens and a spherical root that develops a sweet, mild flavor. Their fast growth rate, with greens ready in about a month and roots maturing in 50 to 70 days, makes them a rewarding crop for gardeners seeking quick results.
The Dual Planting Strategy
Turnips are typically planted with two distinct seasonal goals. Spring plantings are primarily aimed at harvesting the leafy tops, which are tender and less pungent when temperatures are cool. Since the roots require a longer period of cool weather to develop properly, the spring crop often yields smaller, quicker-maturing roots that may be slightly more peppery.
The fall planting is the superior choice for developing the largest, sweetest roots. The plant thrives in a temperature range of 50°F to 70°F. By timing the planting correctly, the roots are allowed to mature during the cooling temperatures of late summer and autumn, which concentrates sugars within the bulb.
Calculating the Spring Planting Window
The spring planting window maximizes the harvest of fresh greens before the summer heat arrives. Seeds should be sown directly into the garden two to four weeks before the average last expected spring frost date. This early start allows the plants to establish themselves while the soil temperature is still cool, ideally around 40°F to 60°F for optimal germination.
The goal is to complete the harvest before daily temperatures consistently exceed 75°F. If temperatures become too warm, the turnip plant “bolts,” prematurely sending up a flower stalk to produce seed. This shift causes the greens to become bitter and the developing roots to turn woody and tough.
Calculating the Fall Planting Window
The fall planting window requires a backward calculation from your region’s first expected hard frost to achieve large, sweet roots. The typical maturity period for Purple Top Turnips is between 60 and 75 days. Count back the average days to maturity from the date of your area’s first hard frost to ensure the roots are fully developed.
Planting should occur in late summer, approximately 8 to 12 weeks before that first hard frost date. This timing allows the turnip bulb to swell and mature during the mild autumn weather. Exposure to a light frost just before harvest is beneficial, as the cold temperature triggers the conversion of starches into sugars within the root, improving the sweetness and flavor profile.
Post-Planting Requirements for Success
Once the timing is correct, success depends on proper planting depth and immediate post-emergence care. Turnip seeds require shallow planting, typically between one-quarter and one-half inch deep, to ensure successful germination. Planting too deep will exhaust the seed’s energy before the seedling can reach the soil surface.
The most important step after the seedlings emerge is thinning, which is necessary for the root to develop into a large, globe shape. Once the plants reach a height of two to three inches, they must be thinned to a final spacing of three to six inches apart. Failure to thin the seedlings results in an overcrowded environment where the roots compete for resources and remain small.