All About Growing Radishes

Large Oriental radishes develop heavy, carrot-shaped roots when grown in the fall.

Rat-tail radishes (R. caudatus) produce edible green seed pods, which can grow to more than 6 inches long.

For more information on types of radishes and our recommended varieties, see ourRadishes at a Glancechart.

When to Plant Radishes

In spring, sow salad radishes at 10-day intervals starting two weeks before your average last spring frost, continuing to three weeks after your last frost date. Sow rat-tail radishes around your last spring frost date.

In fall, sow all types of radishes at two-week intervals starting eight weeks before your first fall frost, continuing up until three weeks before your first frost date.

How to Plant Radishes

When preparing the planting bed, loosen the soil 6 to 10 inches deep, and mix in good compost or well-rotted manure. Sow seeds a half inch deep and 1 inch apart, in rows spaced 12 inches apart. After the seedlings appear, thin salad radishes to 3 inches apart; thin oriental radishes to 8 to 10 inches apart. Seeds typically sprout in three to seven days when sown in 60-degree soil.

Pest and Disease Prevention Tips

Flea beetles make numerous small holes in radish leaves. Cabbage root maggots and cutworms sometimes rasp holes or channels into radish skins. All of these pests are easily prevented by covering the plants with lightweight floating rowcovers.

When sown early and exposed to cold weather, some radishes will bolt (rush to produce flowers) before they develop plump roots. Bolting is rare in radishes grown in late summer and fall.

Harvesting and Storage

When pulling radishes in warm weather, cool them right away by dropping them into a pail of cold water. Use a sharp knife or kitchen shears to remove the leaves, then store in the refrigerator for up to three weeks. Large oriental varieties can be left in the ground well into fall and dug just before the soil freezes.

Harvest salad radishes once they are bigger than grapes. Radishes left in the ground too long develop a pithy texture and often crack following heavy rains.

Hot weather and drought encourage the development of spicy flavor compounds, which are similar to those found in horseradish.

Saving Seeds

To save seeds from open-pollinated varieties, allow three or more plants to bloom together, and wait until the seed pods dry and turn brown before harvesting the seeds. Crush the pods with your hands, winnow or sift them to separate seeds from chaff, and store the seeds in a cool, dry place for up to five years.

Growing Tips

• In spring, cover newly seeded beds with a glass-topped frame or plastic tunnel to warm the soil.
• To save space, sow radishes between rows of slow-germinating vegetables, such as carrots, parsley or parsnips.
• To reduce weed competition, place strips of wet newspaper along the edges of the seeded furrow, and cover them with grass clippings or another biodegradable mulch.
• Thin radishes early, when they have only two or three leaves. Early thinning minimizes disturbance to nearby plant roots.
• Keep the soil constantly moist while radishes are growing. Cool, moist soil is the key to growing a good crop. Root quality is best when the plants are thoroughly drenched with water every three days throughout their growing season.
• Radishes need full sun, but they benefit from partial shade during spells of hot weather. To help the plants get through a spring heat wave, cover them with a shade cover made of lightweight cloth, held aloft with wooden stakes.
• High nitrogen fertilizers will make radishes grow lush leaves, but the roots may never swell into plump radishes. Stick with compost when preparing space for radishes.
• If your soil is heavy clay, salad radishes may grow thin, ropelike roots rather than large, crisp ones. Lightening the soil’s texture by mixing in compost and sand can help, or you can stick with Oriental varieties, which adapt well to clay soil.
• Don’t be discouraged if a spring crop doesn’t meet your expectations. Your best shot at perfect radishes comes in fall, when the soil is getting cooler rather than warmer.
• Radishes make a good fall cover crop. Plant them after beans, peas or another nitrogen-fixing legume, and they will utilize nitrogen left behind in the soil. Later, when the plants are killed by cold winter weather, nitrogen and other nutrients will be returned to the soil.

In the Kitchen

Slice or grate radishes into salads and slaws, or layer them onto sandwiches. You also can try eating radishes the European way — with bread and butter. Radishes braised in butter or sesame oil until they just begin to brown have a mellow flavor and succulent texture. Substitute sliced or diced radishes for water chestnuts in stir-fries. A handful of salad radishes provides about 20 percent of your daily quota of vitamin C, along with about 2 grams of fiber, lutein and a range of minerals.

Contributing editor Barbara Pleasant gardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visiting her website or finding her on Google+.