By Dr. Mercola
Radishes are crisp, colorful and delicious. When served raw or added to salads, radishes add a burst of bold, peppery flavor. The beauty of planting radishes is twofold: They mature in about 25 days and you can grow them in both spring and fall. Radishes are a low-calorie food that is a good source of vitamin C and other antioxidants.
They help detoxify your blood, prevent cancer, purify your kidneys and urinary system and regulate your blood pressure. If you are looking for a fast-growing vegetable to add color and a flavorful zing to salads and other dishes, you may be interested in learning more about how to grow radishes.
Where Did Radishes Come From?
Radishes (Raphanus sativus) are a member of the cabbage or brassicas family, also known as cruciferous vegetables. Some of the close relatives of radishes are broccoli, Brussels sprouts, cabbage, cauliflower and kale. WebMD shares a few fun facts about radishes:1
- The scientific name for the genus that includes radishes, Raphanus, is Greek for "quickly appearing"
- Although radishes are grown throughout the U.S., California and Florida grow the most
- Radishes were first cultivated in China, and spread throughout the Northern Hemisphere and into Europe in the 1500s
Today, radishes are cultivated and consumed around the world. They are most often served raw, commonly appearing on salads and vegetable trays. Radishes vary in color, flavor, size and time to maturity. The sharp flavor of radishes is the result of chemical compounds produced by the plants, including glucosinolate, isothiocyanate and myrosinase.
In addition to being grown for eating, radishes are also used as a cover crop in winter or as forage for grazing animals. Some varieties, such as daikon, are grown for seed, and still others for sprouting.
Common Radish Varieties
Although there are many varieties from which to choose, a few of the most common types of radishes include the following:2
- Cherry Belle is the round, red radish commonly found at your local supermarket
- Daikon Long White is a huge radish measuring up to 3 inches in diameter and 18 inches long
- French Breakfast is a mild, extra-crunchy radish that is good raw or cooked, and has a slightly pungent taste
- Rat Tail3 is a tasty, edible podded radish grown for its crunchy, tangy seed pods; this variety can tolerate hot weather, resists pests and never forms bulbs
- White Beauty is a small, round radish that is white inside and out, with a sweet, juicy flavor
Daikon Radish: Japan’s Most Popular Vegetable
According to The Japan Times,4 the daikon radish has been noted as Japan’s most popular vegetable, outpacing cabbage and onions in popularity. Its white roots and green tops are eaten year-round in various forms: cooked, dried, pickled, raw and sprouted. Radishes have been part of Japanese cuisine for millennia, but only the green tops were eaten originally. Now, the entire radish is eaten, and 90 percent of daikon radishes are grown and consumed in Japan.5
Raw grated daikon (known as daikon oroshi) has a taste less pungent than, but similar to, horseradish. This ubiquitous Japanese condiment is served with many meat and fish dishes, and is also added to sauces for soba noodles and tempura. Particularly during the winter months, dried daikon and pickled daikon are important staples of the Japanese diet.
Some Japanese mix daikon oroshi with plain yogurt and honey to make a concoction that is believed to promote regular bowel movements. About daikon greens, the University of Illinois Extension said:6
“Daikon greens are delicious too. They can be washed, stacked, rolled into a scroll, and cut crosswise. This produces thin julienne strips which are traditionally salted and left standing for an hour. The moisture is squeezed out. The leaves are then chopped and stored in glass jars for up to a week in the refrigerator. The Japanese stir them into warm rice, [and] they can also be added to soups and other recipes.”
How to Grow Radishes
Regardless of the variety you choose, if you are new to vegetable gardening or want to teach your children to garden, radishes are an easy beginner’s crop. They grow well from direct seeding (less well from transplants) and mature quickly. Within a few days of the seeds going into the ground, you will see tiny plants poking their heads above the soil.
If you plant Cherry Belle or French Breakfast, you will be eating fully formed radishes in about 25 days. Although radishes are hardy and would do well in most soil conditions, below are a few of the main variables to consider when planting them:7,8
• Soil: Radishes will thrive in loosely packed, well-drained soil. Choose soil with a neutral pH and ensure it is kept moist. Do not add nitrogen or other nutrients because they may interfere with the growth of radish bulbs. Also, avoid planting your radishes in hard-packed soil, which may make it difficult for the bulbs to form properly.
Avoid planting radishes in the same place year after year. For best results, practice a three-year crop rotation. If you are concerned about the condition of your soil, review these soil restoration techniques.
• Spacing: Direct sow your radish seeds one-half inch deep and about one-half inch apart. Set your rows 12 inches apart. When the plants are about 2 inches tall, thin them to 1 to 2 inches apart for standard varieties and 3 to 6 inches apart for larger winter varieties. Radishes will not grow well if they are crowded.
• Sun: Radishes are a cool-weather crop but require full sun for maximum yield. If planted in excessive shade — or even if they are overly shaded by larger vegetables growing near them — radishes will put their energy into producing larger leaves. This impressive top-level growth will steal nutrients from the roots and you’ll end up with immature bulbs. Radishes do not do well in intense heat, so suspend growing during the hot summer months.
• Timing: Plant radishes in the spring, as soon as you can work the soil, but while the overnight temperatures are still in the 40- to 50-degree F range. The best timing is generally about four to six weeks before the last expected frost in your area. To ensure a ready supply of radishes throughout the growing season, sow seeds biweekly (or weekly if you are a radish lover) through midsummer. If a fall harvest is desired, begin sowing seeds in late summer through the first hard frost.
• Watering: For quick growth and the best flavor, keep the soil evenly moist, but not waterlogged. Because they produce bulbs, radishes need adequate and consistent moisture throughout the growing season. Radishes that are dry will crack and split open. Cracking will negatively affect the flavor and diminish the aesthetics of your radish crop.
Troubleshooting the Top Four Radish Growing Problems
While radishes are one of the fastest and easiest vegetables to grow, there are a few problems known to plague beginning or inexperienced gardeners. Garden experts from The Spruce share the following advice related to the four most common problems associated with growing radishes:9
- Radishes that are too hot: The best way to control the intensity of the flavor of your radishes is to harvest them as soon as they mature. Radishes harvested in a timely manner tend to be smaller, crisp and sweet. Unlike beets and carrots, the sweetness of radishes does not improve when they are left in the ground longer. To the contrary, radishes become tougher and increasingly bitter the longer they are left in the ground.
- Radishes that crack open: Consistent, even watering is the solution to maintaining good-quality radish bulbs. Cracking can be a sign you’ve been underwatering, or, you tried to make up for watering you missed by overwatering. Overwatering can cause your radish bulbs to absorb too much water, swell up quickly and split open. Though not always aesthetically pleasing, split radishes are still edible, so feel free to eat them whole or cut them up for salads.
- Radishes that are tough and woody: Radishes flourish in cool weather with moist soil. If the temperature is too hot and water is scarce, radishes will become tough and woody.
- Radishes with beautiful tops but poorly formed bulbs: If radishes are planted in the shade or are shaded by other larger garden plants, they will put all their energy into creating beautiful tops, while the bulbs will be poorly developed. Thinning is especially important, because radish bulbs will not develop well if you do not give them adequate room to grow.
Companion Plants: Strategic Pest Control
Rodale’s Organic Life suggests the following strategies for pest control as it relates to companion plants that do well with radishes:10
- Sow radishes among your cucumber and squash mounds to help repel cucumber beetles
- Plant radishes near spinach because radishes will attract leafminers away from the spinach; despite damaging radish leaves, leafminers will have no adverse effect on radish bulbs
- In addition to cucumbers and spinach, radishes also do well when planted near beans, lettuce, parsnips and squash
- Avoid planting radishes near potatoes, kohlrabi and turnips
Because it is a member of the cabbage family, radishes can be affected by cabbage maggots.11 Cabbage root maggots are the larvae of the cabbage root fly, which is small, gray and looks like a skinny house fly. After the fly deposits its eggs along the base of radish plants, small, white legless worms are hatched. The cabbage root fly’s eggs hatch only in cool weather, which is why these pests mainly attack radishes and other cool-weather members of the cabbage family.
The best way to protect your radishes from the cabbage root maggot is to use row covers early in the season to prevent the cabbage root fly from laying its eggs near your plants. Fortunately, while cabbage maggots are attracted to radishes, they seldom ruin the whole crop.
Radishes Are a Super Low-Calorie Food
Radishes are surprisingly low in calories. Although it is unlikely you would eat 10 large, raw radishes in one sitting, which equates to roughly a 3.5-ounce serving, it would only amount to 16 calories. That serving size would also give you:
- 3 grams of carbohydrates
- 2 grams of fiber
- 2 grams of sugar
- 1 gram of protein
- 39 milligrams of sodium
One serving of radishes provides 25 percent of your recommended dietary allowance (RDA) of vitamin C, as well as 5 percent of your RDA for potassium, 2.5 percent for magnesium and 2 percent each for both calcium and iron.
You can harvest radishes as soon as their bulbs are fully formed above ground. Pull them as soon as they mature because oversized radishes will inevitably crack, at which point they will become tough, woody and less flavorful. Once harvested, cut the tops off and store unwashed radishes in plastic bags in your refrigerator, where they will last for a week or two. Always wash radishes well before eating them. If you plan to use the radish greens, store them separately and eat them within three to four days.
Radish Recipes: Tips on Eating Radishes
Rodale’s Organic Life offers the following tips on eating radishes:12
- Make radish tzatziki: Grate one bunch of radishes and combine with 1 cup Greek yogurt. Add one minced garlic clove, a pinch of your preferred sweetener and a splash of vinegar. Add dill, kosher salt and freshly cracked black pepper to taste. Use it as a dip for raw vegetables.
- Quick radish pickles: Thinly slice one bunch of radishes and combine with 1/2 cup red wine vinegar, 1/2 cup water, 1/4 teaspoon of your preferred sweetener and 2 teaspoons kosher salt. Place in glass jar with lid and refrigerate for 15 minutes. Eat radish pickles alone, top them with fresh goat cheese or use them as a garnish for tacos.
- Radish crackers: Thinly slice one bunch of radishes and top them with raw, organic grass fed butter or any of your favorite savory spreads.
The Health Benefits of Radishes
Radishes have wonderfully beneficial antibacterial, antifungal, antioxidant, anti-inflammatory and detoxifying properties. They contain the powerful flavonoids beta carotene, lutein and zeaxanthin. According to The Guardian, radishes, similar to other vegetables in the brassica family, are good for you because:13
“[R]adishes contain two natural compounds, sulforaphane and indole-3, which in animal and lab studies have shown an anti-cancer action. It is thought that these antioxidant substances may slow or stop the growth of several different types of cancer, possibly by prompting the body to make higher levels of detoxifying enzymes. Radishes also give you a significant amount of vitamin C to boost your defenses against disease.”
Indoles are detoxifying agents, and sulforaphane is an important isothiocyanate antioxidant compound shown to be an inhibitor of breast, colon, ovarian and prostate cancer. Eating radishes also:14,15
Cleanses your blood of toxins and waste, including excess bilirubin, which causes jaundice
Keeps your digestive system regular and acts as a natural diuretic to help purify and flush your kidneys and urinary system
Inhibits red blood cell damage by supplying fresh oxygen to your blood
Regulates your blood pressure
Relieves congestion and prevents respiratory problems, such as asthma or bronchitis
Soothes dry skin, rashes and other skin disorders
Considering their many health benefits and the ease with which they can be grown in your garden, radishes are a vegetable you may want to consider eating more often.