How to Grow and Care for Radishes

When you think of a radish (Raphanus sativus), you most likely imagine the root vegetable that's small, round, red, and tangy. The most popular radishes fit this description, though radishes can be round or oblong; hot or mild; red, pink, purple, white, or bicolor. Radishes have quick growth rates, with smaller varieties ready in 30 days after sowing and larger ones in about 60 days.

Radishes are annual vegetables that are members of the Brassicaceae family, along with broccoli, cabbage, cauliflower, kale, and collards. They are planted in the spring (for a spring harvest) or late summer (for a fall harvest).

How to Plant Radishes

When to Plant

Direct seed radishes in the garden in the early spring as soon as the ground is workable. Because they mature so quickly, sow seeds weekly (succession sow) to ensure you have an ongoing supply of radishes. You can also plant them again toward the end of summer and early fall, at least four to six weeks before your first fall frost. Stop planting when spring temperatures reach 65 degrees, as they will bolt in the heat.

Selecting a Planting Site

Pick a sunny spot with rich, loose, well-draining soil. Container growing is also an option. Because radishes grow quickly, they can be planted between slower-to-sprout plants, such as carrots, in the vegetable garden. The radishes will be harvested before the other plants need the space. Plus, radishes are good for loosening and cultivating the soil. Just make sure no nearby plants will shade out your radishes.

Spacing, Depth, and Support

Sow seeds around 1/2 inch deep and 1 to 2 inches apart. Thin seedlings to 3 inches apart. Rows should be spaced three inches apart. A support structure won't be necessary.

Radish Plant Care

Light

Radish plants need full sun, meaning at least six hours of direct sunlight on most days. Radishes grown in too much shade will put energy into leaf growth rather than root growth.

Soil

Radishes do best in rich, loamy, or sandy, well-draining soil with a slightly acidic to neutral soil pH (6 to 7). The soil must not be heavy or compacted, as the roots won't grow well in those conditions.

Water

Radish plants typically need 1 inch of water per week. Soil that's too dry can cause the plant to bolt (go to seed) and ruin the taste of the radishes, making it pithy, and soil that's too wet can cause the roots to split and rot. A layer of mulch around the plants can help to maintain soil moisture.

Temperature and Humidity

Radishes like temperatures between 40 and 70 degrees Fahrenheit, with temperatures in the low 60s being best. Hot weather can cause the plants to bolt and decline in quality. They can get tough and woody or spongy with hollow centers. Also, once a radish bolts, the bulb stops forming. Humidity isn't an issue as long as adequate soil moisture is maintained and there is good airflow around the plants.

Fertilizer

If you’re already starting with rich soil, you typically won’t need to fertilize radishes. If you need to improve your soil, work in a few inches of compost before planting.

Pollination

Bees and other pollinators will pollinate radish plants. And radish varieties will cross-pollinate with one another. 

Types of Radishes

Some of the best radish varieties differ based on their appearance and time to harvest. They include:

• 'Cherry Belle': This is an early spring variety that's red and round. It matures in around 22 days.
• 'French Breakfast': This is a heat-tolerant variety that's oblong with a red and white color. It matures in around 23 days.
• 'Scarlet Globe': Easy variety to grow, bright red with white, crisp flesh, and a mild flavor.
• 'Golden Helios': Matures in about 25 days, has purple-streaked leaves and can handle heat better than other varieties.
  
• 'Daikon': This variety grows well in cool climates, maturing in around 60 days. It's long and white and has a mild flavor.

Radishes vs. Turnips

As root vegetables, radishes and turnips have a similar look to them. But there are some notable differences. Radishes are generally smaller than turnips and have a nuttier and spicier flavor. Turnips usually have a more subtle, earthy flavor.

Harvesting Radishes

Take note of when your radish variety should be ready for harvesting. In general, harvest when the roots are around 1 inch in diameter. You can often see the shoulders of the radish rising slightly above the soil line. You might have to pull one out to see whether it's ready.

Don't wait too long to harvest to ensure a pleasant flavor and tender texture. Left in too long, your radishes will taste too hot and pithy. Hot weather can also ruin this cold weather crop's taste.

To harvest, pull up the plants, and cut off the tops and the thin roots. Leaving the leaves on will draw moisture and nutrients from the radish bulb. The greens can be stored in the refrigerator for a few days and eaten fresh or cooked. The bulbs can be stored in the refrigerator's vegetable crisper for one to two weeks. They also are good fresh or cooked in salads, soups, and more.

How to Grow Radishes in Pots

Container growing is a good option if you don’t have garden space or the loose soil that radishes need. Common radish roots are shallow, so they don’t require that deep of a pot. But it’s best to grow a round variety rather than a long one to ensure it has enough room to develop.

A container around 8 to 12 inches wide and deep should be fine. It also should have ample drainage holes. Unglazed clay containers are beneficial because they’ll allow excess soil moisture to evaporate through their walls, helping to prevent root rot. Use any high-quality potting soil. Containers dry out more quickly and need more watering than in-ground gardens. Monitor moisture closely.

If you consider planting in a 5-gallon container, you can evenly space the seeds, yielding about 10 radishes.

Pruning

You won’t have to do any pruning on your radish plants beyond thinning seedlings. If the radishes remain crowded, they won’t develop properly. Fortunately, you can eat the seedlings you thin. Snip them off at ground level rather than pulling up their roots to avoid disturbing the roots of neighboring plants. 

Propagating Radishes

Radishes are typically grown from seed. Growing radishes from root scraps is possible, but that method is unreliable and not recommended. Seeds up to five years old are a much better bet.

The best time to plant seeds is in early spring and fall when temperatures average about 50 to 70 degrees Fahrenheit. Collect seeds from mature plants for future plants. Here’s how to harvest the seeds:

1. Rather than pulling the radishes as they mature, allow the plant to remain in the ground. Eventually, it will send up a flower stalk and produce seed pods. 
2. Remove mature seed pods once they’ve turned brown and dried out. Crush the pods to release the seeds. Separate the seeds from the rest of the pods.
3. Place the seeds in a paper envelope, and store them in a cool, dry spot. They should remain viable for five years. 

How to Grow Radishes From Seed

Radishes germinate quickly from seed—usually three to five days—when air temperatures are between 50 to 60 degrees Fahrenheit. One seed yields one radish.

Plant them four to six weeks before you expect your last frost. You can succession sow every 10 days with another set of seeds until the air temperatures reach 65 to 75 degrees. You can also sow again in the late summer and early fall until the winter weather sets in. Remove any weeds around your seedlings to prevent competition for moisture and nutrients. 

Here's how to sow seeds:

• Direct-sow seeds outdoors about 1/2-inch deep.
• Cover loosely with soil. Space each seed 1 inch apart in rows 3 inches apart. 
• Water seeds thoroughly, down to 6 inches deep.

For larger varieties of radishes, like daikon, sow seeds slightly deeper than the small varieties. Gently firm the soil around the seeds, and keep it evenly moist but not soggy. Germination should occur in three to 10 days.

Overwintering

Radishes are annuals, meaning they complete their life cycle in one growing season. So no overwintering will be necessary.

Common Pests and Plant Diseases

Cabbage maggots are common pests for radish plants, as they will tunnel into the radishes. Cutworms also feed on radishes. And flea beetles will feed on radish leaves but won't injure the bulbs. Monitor to catch these insects before they destroy the whole crop. Growing your radishes under floating row covers can help to prevent pest issues. Wood ash mixed into the soil can help deter root maggots. Some radish plants' diseases include downy mildew, black root, and scab. But maintaining proper growing conditions can prevent many problems with diseases.