When you think of a radish (Raphanus sativus), you most likely imagine the root vegetable that's small, round, red, and tangy. By far, the most popular radishes eaten and grown fit this description. Although there are longer varieties and different colors of radishes, small round radishes are such quick and easy growers that they virtually define what a radish should be. And yet, even this humble globe-shaped radish offers a good amount of variety. They can be round or oblong, hot or mild, red, pink, purple, white or bi-colored.
The Asian radish varieties are often referred to as winter radishes because they mature late in the season and can be stored over winter. Daikon is a Japanese word meaning “great root,” and some of these radishes can indeed become great in size, although not all Asian radishes are long. The black radishes, including black Spanish radish, tend to be the hottest.
Don’t forget that the tops or greens of radishes are also edible, as are the pods. There are even varieties, like 'Rat's Tail' radish, that are grown specifically for their pungent pods, which grow all summer long.
Radishes are annual vegetables that are members of the Brassicaceae or Cruciferous family, along with broccoli, cabbage, cauliflower, kale, and collards. They are started from seed in spring (for a spring harvest) or late summer (for a fall harvest). Some of the smaller radishes mature in as few as 25 days. The larger winter radishes can keep you waiting for up to 60 days.
|Botanical Name||Raphanus sativus|
|Common Name||Radish, common radish, garden radish, rabone|
|Mature Size||2 to 3 feet tall, 1 to 2 feet wide|
|Sun Exposure||Fun sun, partial shade|
|Soil Type||Rich, well-draining|
|Soil pH||Acidic to neutral (6.0 to 7.0)|
|Bloom Time||Flowers are not showy|
|Flower Color||White to violet|
|Hardiness Zones||Annual plants grown in all zones (USDA)|
How to Plant Radishes
Radishes, like most vegetables grown for their roots, are direct seeded in the garden. They can be started very early in the spring, as soon as the ground is relatively dry, and again toward the end of summer for a fall garden, and even in late fall with the protection of a cold frame. Since radishes grow quickly, they can be squeezed in between other plants in the vegetable garden. The radishes will be harvested before the other vegetables need the extra room. Plus, radishes are good for loosening and cultivating the soil for slower-to-sprout vegetables, like carrots.
Sow seeds 1/4 to 1/2 inch deep. You’ll want at least 2 inches between plants, but seedlings can be thinned and eaten when they are 1 to 2 inches tall.
Radish plants need full sun to partial shade. The common, small radishes must grow quickly in cool weather, so they need plenty of sun.
Radishes do best in rich, well-draining soil with a slightly acidic to neutral pH of 6.0 to 7.0. Most important, the soil must be loose and not compacted. The roots will no grow well in hard or rocky soil. Sandy soil and loam are best.
Radish plants typically need 1 inch of water per week. Soak the soil as needed (more frequently if the soil drains very quickly) to reach the roots, depending on the type of radish you're growing.
Temperature and Humidity
Radishes are a cool-season vegetable that can mature very quickly. The small, round varieties will get woody if grown in hot temperatures. Radishes decline in quality when the temperature warms. They can get tough and woody or spongy with hollow centers. Once a radish bolts, or goes to seed, the bulb stops forming.
Since radishes are so quick-growing, they do not require fertilizing, as long as you start with rich soil. If necessary, improve the soil with compost prior to planting.
- 'Cherry Belle': Round, red; matures in 22 days
- 'Early Scarlet Globe': Round, red; matures in 22 days
- 'Easter Egg': Oval, mixed colors; matures in 25 days
- 'French Breakfast': Oblong, red/white base; matures in 23 days
- 'Icicle': Long and slender, white; matures in 25 days
- 'Rat Tailed': Grown for its edible pods, not its root; matures in 45 to 50 days
- 'China Rose': Red skin, white flesh; matures in 52 days
- 'Round Black Spanish': Black skin, white flesh; matures in 55 days
- Daikon: Long, white; mild flavor; matures in 60 days
Check the size of your radish bulbs frequently to ensure that you harvest before the plants begin to decline. You can feel the size of the tops just below the soil line, or you can pull a few to check. To have a continual harvest, succession-sow a new crop every 10 to 14 days, until it gets too warm. Most radishes bolt to seed in hot weather. The edible-podded radishes are a great substitute during summer since you want them to go to seed.
- Spring radishes: The fast-maturing, round radishes are ready for harvest in three to four weeks. You’ll usually see the top portion of the radish poking up through the soil. When it appears to be almost an inch across, it is ready to pick. Radishes can be harvested by pulling or by gently loosening the surrounding soil. Don’t let mature radishes sit in the ground or they will get either woody or spongy.
- Winter radishes: The long, Asian radish varieties take longer to mature, sometimes up to three months. They should be harvested before the ground freezes and can be stored for several months.
The thinned plants of all varieties are edible and can be used as salad greens, in sandwiches, or floating on soups. To store radishes, remove the green tops and store the bulbs and tops separately. Leaving the leaves on will draw moisture and nutrients from the radish bulb. The globe-shaped radishes can be stored in the refrigerator, in a sealed container, for about a week. Winter radishes will last about two weeks in the fridge or several months in cold storage.
Cabbage root maggots are most common in northern gardens, where they will tunnel into radishes. Cutworms can also feed on radishes. Flea beetles will make Swiss cheese of radish leaves, but they do not injure the bulb. Monitor to catch these insects before they destroy the whole crop. You can avoid them almost entirely by growing your radishes under row covers.
How to Grow Radishes in Pots
Fast-growing spring radishes grow quite well in pots, and growing them this way is a good option if you are plagued by root maggots. They will need at least 4 inches of soil depth and lots of water.