Turnips are available most of the year through grocery stores and farmers’ markets, but usually only the standard purple and white varieties. Growing your own from seed opens a world of different varieties with a wide range of colors and flavors from spicy, like radishes, to smooth, mild, almost apple-like sweetness. Plus you can harvest when you want, while they are small, tender and sweeter, and save seed for following years.
Planting Turnip Seeds
When you buy a packet of turnip seeds, they will be surprisingly small. At nearly two hundred thousand seeds per pound, even a small packet can provide a lot of turnip plants!
Turnips grow best in cool weather; hot temperatures cause the roots to become woody and bad-tasting. They are typically planted in March, April, or May, depending on soil temperature and late freeze predictions; in areas with long seasons they can be planted again in August, September or October.
Sow seed onto fertile, well-drained soil. Turnip seeds sprout best, within a week or two, between 60 and 70 degrees F; however, if sown in cooler soils, down into the mid 40s, they take longer to sprout. Keep soil moist and the plants will grow quickly, being ready for harvest between 40 and 60 days after planting seed.
Though hybrids rarely come true from saved seed, heirloom turnip varieties are “open pollinated” meaning you can save seed from year to year with the same results, as long as you don’t have different varieties flowering at the same tine very close to one another.
However, though turnips are planted as one-shot annuals in the garden, they are actually biennials – the first season they grow leaves and store nutrients in the thickened root; the second year they sprout tall spires of yellow flowers followed by pea-like pods of seeds, then die. While a few spring-planted varieties such as popular Shogoin will flower and make seed at the end ofthe first season, most have to go through a dormant period first.
In mild winter areas, roots can be mulched and left in place, and they will flower early the next spring. But in very cold areas, gardeners harvest a few large, mature roots from fall-planted turnips before they freeze, cut off the leaves leaving a few inches of leaf stem, then store the roots, unwashed, in a cool, dark, humid place over the winter. They set the roots back in the ground in the spring, which quickly sprout leaves and begin to flower and make seeds.
Wait until the seed pods turn brown and dry, and shake them into a paper bag where they will continue to dry before shattering. Clean them through a kitchen sieve, blowing away the chaff, then store the darkest ones in a cool, dry place for up to four or five years. It is always a good idea to replenish your heirloom turnip seed supply every two or three years.