Unlike the Asian brassicas, which share similar flavor characteristics, the root brassicas are quite diverse, ranging from starchy rutabagas to sinus-clearing horseradish. Wasabi deserves a mention as being part of this illustrious group even though fresh wasabi is so challenging to find and so expensive if you do find it. Although kohlrabi is actually a swollen stem not a root, I have slipped it in here because it fits in this article the best.
There are two basic categories of radishes, table radishes and Asian radishes. The former, most often spotted in salads, are crisp and juicy and have a hot, peppery finish. Cooking sweetens them, muting their bite. Asian radishes such as daikon are crisp and juicy, as well, but have a milder flavor.
SELECTION: Table radishes—French breakfast, Icicle, Easter Egg, and Cherry Belle are popular varieties—are sold in bunches. They are typically round or cylindrical and come in several colors, such as white, pink, red, or purple with pure white interiors. Choose firm radishes with no cracks or dry areas, ideally topped with fresh-looking greens. An average bunch contains 8 to 12 radishes.
Daikon radishes are the most common Asian radishes found in supermarkets. These thick cylinders are sold individually, should feel firm, smooth, and heavy for their size, and sometimes weigh up to a few pounds each. Their skin is whitish, sometimes tinted with pale green, and their flesh is ivory.
PREP: If you purchase radishes with greens attached, remove the greens and store them separately. Store radishes in a loosely sealed plastic bag, along with a paper towel to wick away excess moisture. Refrigerate table radishes for no more than 5 to 7 days; daikon radishes will keep for up to a few weeks. Wrap the greens in a paper towel and store them in a loosely sealed plastic bag for no more than 2 to 3 days.
When ready to cook, scrub daikon radishes under running water, then peel them. Table radishes are usually quite dirty. I often soak them in a bowl of water for a few minutes—especially the greens—and agitate them in the water to remove any hidden grit. Repeat this process as needed. Trim the stem and the rootlets from radishes before serving. Keep in mind that although table radishes are usually seen raw, they are also delicious roasted or braised. Cooking sweetens them and mellows their sharp bite. Daikon radishes can be served raw or simmered in soups and stews.
NUTRITION: Radishes are good sources of vitamins C, A, and B6, as well as calcium, magnesium, and potassium. They have about 20 calories per cup.
If you fear turnips as harsh and aggressive, try a bunch of Tokyo turnips in the spring. Sometimes called baby turnips or Japanese turnips, these small, round, white turnips (they have white interiors, too) have a delightful mild, grassy flavor and sweet, juicy texture that will instantly change your mind. Try them sautéed or even raw. Purple-topped storage turnips have a more pronounced flavor that builds as you eat them, but their distinctive pepperiness works well in warming winter stews and braises.
SELECTION: Look for bunches of Tokyo turnips topped with fresh green leaves. The turnips should have smooth skin with no cracks or soft spots; avoid wilted or yellowed leaves. The size of a bunch varies but averages 9 to 12 ounces. Tokyo turnips can be hard to find; look for them in Asian markets or farmers’ markets. Purple-topped turnips are sold individually and average around 6 ounces each. These turnips are white with light purple tops and white interiors. They should feel heavy for their size and be smooth and crack-free.
PREP: If you purchase small turnips with greens attached, remove the greens, discarding the connective stems, and store them separately. Refrigerate turnips in a loosely sealed plastic bag with a paper towel to absorb excess moisture. Tokyo turnips will keep for no more than 3 to 5 days, and purple-topped turnips will keep for up to a few weeks. Wrap the greens in a paper towel and store them in a plastic bag for a day or two. Small young turnips do not need to be peeled but rinse them well before using. Scrub large turnips under running water and peel them before cooking. Wash the greens well and spin them dry.
NUTRITION: Turnips are good sources of vitamin C; the greens are more nutritious than the roots, containing vitamins A and K, folate, and calcium, as well. Turnips have about 35 calories per cup; their greens contain about 17 calories per cup.
Rutabaga (also known as swede)
I am not sure why people think poorly of rutabagas. For the most part, they taste “rooty,” with a mild sweetness that isn’t particularly pungent or aggressive. Some can taste slightly bitter, though still tamer than turnips. Their flesh is starchy and dry, making them almost potato-like in effect. Try them roasted, simmered, or braised.
SELECTION: Rutabagas are cream colored with purple tops (as opposed to the white-and-purple combination of turnips) and a creamy pale interior. They are often coated in wax for storage purposes, though try to choose small (7 or 8 ounces each), unwaxed rutabagas whenever possible. Rutabagas are sold individually and almost never have leaves attached. Choose smaller specimens that feel firm and heavy for their size and are free of cracks or soft spots.
PREP: Store rutabagas in a loosely sealed plastic bag with a paper towel to wick away extra moisture. They will keep in the refrigerator for 2 to 4 weeks. Scrub rutabagas under running water and peel them before cooking.
NUTRITION: Rutabagas are high in potassium, calcium, magnesium, fiber, and vitamins A and C. They contain about 50 calories per cup.
Eating horseradish can provoke one of those pleasure-in-pain moments, vapors sweeping through your sinus cavity with apt precision. Yes, horseradish is pungent and sharp, possibly even tear provoking, but it is also fun to eat.
SELECTION: Choose very firm to hard horseradish roots; limp specimens will be spongy inside. Horseradish is light brown, likely covered with dirt, with creamy white flesh inside. Avoid horseradish roots that are green or moldy.
PREP: Wrap horseradish root in a damp paper towel and store it in a sealed plastic bag in the refrigerator for up to a few weeks. When you are ready to use it, scrub the root, trim the ends, and peel only as much as you will need. Grate the horseradish on the small holes of a box grater or in a food processor. Watch your eyes, however. Horseradish develops its pungency when grated and will throw off some serious fumes. Wear protective goggles if you are particularly sensitive (seriously), or back away as you remove the lid from the food processor. Toss the grated horseradish with a touch of lemon juice or vinegar to prevent browning. Use horseradish raw or add it toward the end of cooking, since heat somewhat diminishes its pungency.
NUTRITION: It would be hard to consume enough horseradish to matter nutritionally, but it does contain vitamin C, potassium, and antibacterial properties.
Not only pungent but also sweet and fragrant, wasabi is most often seen as an accompaniment to sushi. The roots are very expensive and hard to find; check online sources or Asian markets. Freshly grated wasabi is a real treat; be aware that most “wasabi” you are served is actually powdered horseradish or mustard that has been colored with green food coloring. Seek out restaurants that serve the real deal.
Such a charming little vegetable, kohlrabi tastes mild and sweet, somewhat reminiscent of broccoli stalks with a faint peppery, turniplike finish. The leaves taste similar to collard greens. Kohlrabi is very juicy and crisp and is at its finest when served raw, though it also braises well.
SELECTION: Kohlrabi is sold either as a single bulb or in bunches, with or without leaves attached. The bulb will be either light green or purple, connected to its dark green leaves by a series of thin stems. The interior flesh is white. Choose small kohlrabies—about the size of a baseball—that are smooth and free of cracks. Leaves should be thick and vibrant, not yellowed or wilted.
PREP: Separate the leaves from the kohlrabi bulb, discarding the connective stems. Store the bulbs in a loosely sealed plastic bag along with a paper towel to wick away extra moisture. Refrigerate them for no more than 5 to 7 days. Wrap the greens in a paper towel and store them in a loosely sealed plastic bag for a day or two. Use a knife to peel the kohlrabi deeply, removing any fibrous flesh. When cooking the leaves, remove the center rib if particularly thick.
NUTRITION: Kohlrabi is high in vitamin C, potassium, fiber, and B vitamins. It has about 36 calories per cup.