Botanical Names: Brassica rapa, Brassica napobrassica
Turnips (Brassica rapa) and their greens have been grown for thousands of years for both staple human food and livestock fodder. Their roots and leaves are highly nutritious, and the plants are easy to grow and fast to mature enough to harvest within two months of sowing seed.
Turnip plants need sun, well-drained fertile soil, and water every week or two to keep them growing actively instead of slowing down and getting tough and pungent. As they grow, thin plants so the ones remaining can get larger roots; large-rooted varieties need four or five inches between plants.
Because turnip plants grow best in cool temperatures, and can tolerate frost and light freezes, seeds are best sown in late winter or spring for harvest before it gets very hot and roots get tough and bitter, or in the late summer or fall to harvest before a hard freeze kills the plants.
When to harvest turnips depends on whether they are being grown as greens only, as small tender mixed turnips and greens, or as larger mature roots for storage. Harvesting turnips is easy, either by pulling or digging plants entirely or cutting older, mature leaves, a few at a time, from growing plants.
Simply snip off a few leaves as the plants grow, and supplement them with thinned plants which will be tender and sweeter than older plants. Remove only two to four leaves per plant to allow what is left to keep the plants growing strongly. Store them in the refrigerator for up to several days.
Note: Unlike their larger, smooth-leaf rutabaga cousins (Brassica napobrassica), which are across between turnips and cabbages, turnip leaves are finely hairy, and tend to hold any dirt that splashes on them during rains and watering. Be sure to wash them thoroughly after harvest and before cooking, changing the water several times.
Small roots are the most tender, so pull them when they are less than 3 inches in diameter. Harvest small turnips after a month or so of growing, with simple hand pulling; larger ones take up to two months and should be lifted with a shovel or garden fork. Note: Rutabagas are grown just like turnips, but take a month or two longer to mature before harvest. Trim off taproots, and twist off the greens leaving a little bit to protect the top of the root.
Small turnip roots can be kept for two or three weeks in the refrigerator, but store larger ones in a cool, dark basement, garage, or root cellar, where they will keep for several months. Gardeners in mild climates can leave a few in the ground, covering the mature roots with hay or straw enough to keep them from freezing.