Growing Guide: Radish
Download: Radish Growing Guide
What comes to mind when you hear the word "radish?" Cherry-red, ping pong-sized spheres that add spicy-hot crunch to salads? Or are cleverly carved into "radish rose" garnishes? These may be the most popular uses, but radishes can offer so much more! Depending on the variety, they can also be sautéed, roasted, grilled, and stir-fried; diced into soups and stews; or pickled and fermented into delicacies like Korean kimchi.
There are dozens of types of radishes in a variety of shapes, colors, and flavors: Round to tapered. Thumb-sized to foot-long. With skin in shades of red, pink, black, white, and green. Some have colorful flesh, too. All have some degree of spiciness or heat — from pleasingly piquant French breakfast radishes to pungent and peppery Spanish radishes.
Best of all, radishes are easy and fun to grow!
- Radishes are in the brassica (mustard or cabbage) family and are related to broccoli, cauliflower, and kale.
- The scientific name is Raphanus sativus. The genus name Raphanus is Greek for "quickly appearing." The species name sativus is a botanical term derived from Latin that is often used for plants that promote good health.
- The species is thought to have originated in Southeast Asia, though no one knows for sure. They were domesticated in Europe in pre-Roman times and are now grown worldwide.
- Radishes are a good source of vitamin C and contain folate, fiber, riboflavin and potassium, as well as copper, vitamin B6, magnesium, manganese, and calcium.
- The skin of a radish contains much of the spiciness, so if you prefer a mellower flavor, peel it first.
- Radish greens are edible, too. Pluck a few young, tender greens to add to sandwiches and salads. Older greens can be sautéed or steamed. Don't overdo it, though. Harvest just a few leaves per plant so the remaining ones can supply (through photosynthesis) the energy the plant needs to form roots.
- A celebration called "The Night of the Radishes" takes place every December 23rd in Oaxaca, Mexico. Giant radishes are carved into figures of saints and scenes of the Nativity.
- Old-time Vermonters use the phrase "had the radish" to refer to something no longer functioning properly, as in, "That old toaster has had the radish. It's time for a new one."
Types of Radishes
Fast, easy, and so rewarding, these cool-season crops are some of the first to sow in spring, and are ready to harvest in as little as three weeks. For gardeners, that's pretty close to instant gratification! Along with early greens, they'll be in your first harvest basket of the year.
Because their seeds germinate so quickly — often in just three or four days — radishes can be used as living row markers. For example, sow a row of radish seeds between rows of slower-germinating carrot seeds. The radish sprouts will remind you that the area has been planted and the roots will be ready to harvest long before the carrots need the space. Examples of spring radishes include:
Globe radishes. Cherry Belle is an example of the familiar cherry red-skinned, white-fleshed supermarket variety. Other globe varieties boast skins in a range of hues, including white, pink, and purple. They're sometimes sold in mixed bunches (or in mixed seed packets) called "Easter radishes" because they resemble dyed Easter eggs.
French breakfast radishes. Similar to round varieties but more elongated, French radishes tend to have a milder, somewhat sweet flavor. As the name implies, they were once served with butter and salt as a mid-morning snack.
Sometimes called "storage radishes," these varieties take longer to reach maturity — up to 10 weeks. They're generally sown in mid to late summer. You can harvest them small for fresh eating, or wait until they size up. They store well right in the ground — simply dig them as you need them. Once air temperatures drop but before the ground freezes, mulch the radishes with a layer of hay and so you can continue to harvest. However, be sure to dig up all remaining radishes if bitter cold threatens to freeze the soil. Store them in a cool, dark place protected from rodents. Examples of winter radishes include:
Watermelon radishes. With green skins covering a thin layer of white flesh and bright watermelon-pink interiors, they resemble miniatures of their namesake melons. A delight sliced into salads, they're also a favorite for pickling.
Korean radishes. Pale green skin surrounds snow-white flesh on 8", elongated roots. Flavor ranges from slightly sweet to zesty-hot and they have a particularly long storage life.
Daikon radishes. Once found only in specialty markets, daikon (pronounced dye'-con) radishes are now readily available. Sliced thinly and served raw, they add a mild zest and pleasing crunch to salads and vegetable plates. Roast them, add to stir-fries, or grate them into soups and their flavor mellows further. Daikons grow up to 18" long.
Black radishes (aka Spanish radishes). Cut open the black, pebbly skin to reveal the bright white flesh. The sharp, spicy flavor brightens salads and, when thinly sliced, the contrasting skin and flesh make them a beautiful garnish. Roasting black radishes mellows their flavor. Black radishes grow about 8" long.
How to Grow Spring Radishes
If possible, prepare the planting area in the fall, prior to early spring planting. Raised beds are ideal because the soil tends to stay loose and dries out earlier in spring compared to in-ground beds. You can also grow radishes in planters.
Site selection and preparation. Choose a location in full sun with well-drained soil. Loosen the soil to a depth of 8" and remove any rocks. This will ensure that the roots can grow without obstructions. Add some compost or other organic matter, but avoid high-nitrogen fertilizers, which will promote lush foliage at the expense of roots. Radishes prefer a neutral to very slightly acidic soil with a pH of 6.5 to 7.0.
Sowing seeds. Plan to sow seeds directly in the garden about 4 to 6 weeks before the average last spring frost date. Plant seeds 1/2" to 1" deep and about an inch apart. Keep the seedbed moist and the seeds will often germinate in just three or four days.
For a longer harvest season, sow small amounts of seed every week or ten days — this is called succession planting. However, when daytime temperatures reach and stay in the 60s, it's time to stop sowing, because in hot weather radish roots get woody and the plants will bolt (send up flower stalks). Some radish varieties are more tolerant of heat than others; look for varieties described as "bolt-resistant," such as the heirlooms 'Giant of Sicily' and 'White Icicle'.
Note: In regions where summer heat arrives early, "spring" radishes are normally planted when air and soil temperatures cool down in autumn.
Care. When the plants are an inch or two tall, thin them to 2" apart in the row. (Use the washed thinnings in salads.) Water as needed to keep the soil evenly moist but not waterlogged. A thin layer of straw around the plants will help conserve moisture and keep the soil cooler.
Pests. Radishes are generally pest-free. If you see tiny "shotgun" holes in the leaves, they're probably the work of flea beetles — tiny black beetles that will quickly hop away if disturbed. They general cause minimal damage.
Harvesting. About three weeks after sowing, gentle pull soil away from the base of a few plants to see if any fleshy roots have formed. Check the variety description to determine the ideal harvest size. For round radishes, the best size is usually when they're about 1" in diameter.
How to Grow Winter Radishes
Follow the instructions above, with the following changes:
- Loosen soil to the depth of the mature root — up to 18" for daikons.
- Sow the seeds in mid to late summer, or about eight weeks before your first fall frost date. (Avoid sowing in spring; winter varieties are sensitive to day length and will bolt in early summer, before they form edible roots.)
- Thin seedlings to 4" apart to allow room for the larger roots.
- Harvest roots as you need them; they'll keep well in the cool autumn soil. Harvest all roots before the ground freezes.