Turnip

Turnip (Brassica rapa subsp. rapa) is a cool-season root crop in the mustard and cabbage family, Brassicaceae, grown worldwide in temperate climates for its swollen, fleshy taproot and its leafy “turnip greens.”13 Both the root and the leaves are widely eaten by people and fed to livestock, making it an unusually versatile crop for a small holding.23 The species is native throughout Europe, Russia, and Asia, with Europe regarded as a center of origin for subspecies rapa; turnips have been cultivated there since at least Roman times, and were grown in what is now France by around 100 A.D.14 For a homesteader, the appeal is its dual harvest and tolerance of cool weather: one sowing yields both a storable root and a cut of edible greens, and it fits the spring and fall shoulders of the season when warmth-loving crops are done.4

Turnip is usually a biennial: in its first year it forms a low basal rosette of leaves and a swollen root, and in its second year it sends up flowering stems and sets seed, though under some conditions it behaves as a winter annual.13 The edible “turnip” is a wide, swollen taproot that may be round, flat, or cylindrical, and yellow or white, often flushed green, red, or purple near the crown.4 Table varieties are small and tender, while large fodder types can be far bigger — some reaching roughly fifty pounds — and are grown mainly as livestock feed.23 The leaves are green and, in wild forms, somewhat hairy or bristly; cultivated greens are tender, mildly cabbage-like, and carry a slightly spicy, mustard-like flavor raw or cooked.35

Growing turnip

Turnip is grown from seed only; it does not spread by tubers or runners the way a potato does, so every crop begins with a fresh sowing.23 Treat it as a cool-season brassica grown across temperate regions worldwide: USDA sources describe Brassica rapa as a hardy plant used as a winter annual across a wide range, from sea level up to about 5,000 feet in North America.23 Rather than tying it to a narrow hardiness band, horticultural guidance treats the turnip simply as a cool-weather crop suited to common garden zones wherever spring and fall temperatures stay cool — it tolerates light frosts far better than heat.36

Sow direct into the bed. For a spring crop, sow in early spring, roughly three weeks before the last likely frost; turnip is also sown in mid- to late summer for a fall crop, treating it as a spring and late-summer vegetable rather than a midsummer one.6 Because it prefers cool conditions and dislikes heat, those shoulders of the year are the productive windows.36 Detailed spacing, sowing depth, and days-to-maturity figures are not consistently given in the general references gathered here, so they are left out rather than stated with false precision. In practice, work turnip like other cool-season root brassicas: sow into a well-prepared bed in cool weather, thin the seedlings so the roots can swell, and keep moisture steady so they stay tender rather than woody.36

Harvest and uses

The swollen taproot is the main harvest, lifted from the first-year rosette before the plant runs to flower.14 Small, tender varieties are best for fresh eating, while the largest fodder types are grown chiefly as livestock feed.23 The crop gives two harvests from one planting: the root as a cooked or stored vegetable, and the leafy “turnip greens,” edible raw or cooked with a mild, mustard-like bite.35 Both root and leaves are eaten by people and by stock, so little of the plant goes to waste on a mixed homestead.23

Pollination and identification

Turnip flowers only in its second year, when overwintered plants throw up erect stems topped with clusters of bright yellow, four-petaled cruciform flowers typical of the mustard family.14 These flowers attract bees and other pollinators, so a second-year turnip left to bloom doubles as a useful early nectar source before the beak-tipped seed pods (siliques) ripen.14 For most table growers the root is pulled before this stage, but leaving a few plants to flower supports pollinators and lets you save seed.14

In the field, recognize turnip by its first-year basal rosette of green, mildly cabbage-like leaves (hairy or bristly in wild forms) above a wide, swollen taproot — round, flat, or cylindrical, white or yellow and often tinged near the crown — and, in year two, by the yellow cruciform flowers and beaked siliques.1345

Safety and cautions

Turnip is generally safe to eat, and both root and greens are common foods.3 Like other brassicas, however, its roots, leaves, and especially its seeds contain glucosinolates, the natural mustard-family compounds behind the plant’s slight pungency.3 Sources note that in large amounts these can irritate the digestive tract and disturb thyroid function in livestock that graze heavily on the crop, so fodder turnips are best fed as part of a mixed ration rather than as the sole feed.3 For people, the general guidance is that those with thyroid disease are usually advised to moderate high-glucosinolate brassicas and to favor cooked over raw forms.3 These are dietary cautions, not medical claims, and ordinary culinary amounts of turnip are widely regarded as safe.3

Sources

1. NatureSpot. “Turnip (Brassica rapa subsp. rapa).” NatureSpot: Wildlife of Leicestershire & Rutland.
2. NordGen. “Brassica rapa.” Nordic Genetic Resource Center, Crop Wild Relatives plant portraits.
3. U.S. Department of Agriculture, NRCS. “Plant Guide: Field Mustard / Turnip (Brassica rapa).” USDA PLANTS Database.
4. Wikipedia. “Turnip.” Wikipedia.
5. Totally Wild UK. “Wild Turnip (Brassica rapa) Identification.”
6. Missouri Botanical Garden. “Brassica rapa (Rapifera Group).” Plant Finder.