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Radish Seed Starting Tips

Radish seedlings

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Radishes grow best in the cooler time of the year. Most are hardy to spring and autumn chills; a few varieties can withstand the summer heat. Sow seeds for small early varieties 4 to 6 weeks before the last frost. Plant midseason or summer varieties in mid to late spring. Late varieties—called winter radishes—should be sown in the garden 10 weeks before the first expected frost.

More tips: How to Grow Radishes

Sow successions of early spring varieties 10 days apart until mid to late spring. Sow successions of midseason varieties every 10 days until midsummer. Resume planting for fall harvest in late August or early September.

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For the best quality and flavor, radishes must make rapid, even growth. Grow radishes in sandy loam or humus-rich, loosely worked soil, and supply ample moisture. If radishes go dry for even a day in warm weather, they will become tough and strong-flavored. Radishes that grow slowly have a pungent flavor and are undesirable.

Radishes remain in prime condition for only a few days, so small plantings at 7 to 10 days intervals are best.

Mild, small, quick-maturing varieties include Scarlet Globe, French Breakfast, and Cherry Belle; these will reach an edible size in 20 to 40 days.

Radish seedlings seed starting
Radish seedlings

Growing tip: Radish is a cool-season crop. Radishes are best grown in spring and fall.

Shorter and cooler days result in radishes with rounder roots. For mild and tender roots, grow radishes rapidly with plenty of moisture in soil rich in aged compost. When growth is interrupted by a lack of soil moisture, radish roots will be hot, tough, and pithy.

Radishes mature in 21 to 35 days depending on the variety.

Radish planting details

  • Sowing depth: Sow seed ½ inch (1.2 cm)
  • Space between plants after thinning: 1-3 inches (2.5-7.6cm)
  • Days to sprout: 5
  • Days to harvest: 21-25
  • Storage period: 1-2 weeks
  • Seeds per 100-row feet: 1 ounce (28 grams)
  • Yield per 100-row feet: 100 pounds (45 kg)
  • Suggested varieties: Cherry Belle, Scarlet Globe, Red Boy, Champion

Radish sowing and planting tips

  • Start radishes from seed sown directly in the garden.
  • Radish seeds are viable for 5 years.
  • Start seeds in the garden about 6 to 4 weeks before you expect the last frost in spring. Radishes can be started indoors, but they—like most root crops—are difficult to transplant to the garden with success.
  • If started indoors and transplanted, allow two additional weeks to maturity as a result of root insult at transplanting; nip off the long thread tip of the radish root when transplanting.
  • Sow seed ¼ to ½ (6-12 mm) inches deep and be sure to heel or stamp the soil firmly.
  • Sow seed 1 inch (2.5 cm) apart and later thin to 4 inches (10 cm) in all directions.
  • To improve germination sow seed at dusk or on a cool, cloudy day.
  • Sow seed in loose, fertile soil. Adding aged compost to planting beds in advance of sowing will feed the soil and aid moisture retention.
  • Seeds should germinate in 4 to 10 days at an optimal temperature of 70°F (21C) or greater; germination will take longer in colder soil.
  • The optimum soil temperature to grow radishes is 50° to 75°F (10-24°C).
  • Make additional sowing at 3-week intervals for a continuous harvest, but time sowing so that the crop does not mature in hot weather.
  • Radishes prefer a soil pH range of 5.5 to 6.5.
  • Grow radishes in full sun for best yield—tolerates partial shade.
  • Fertilize with an organic fertilizer such as fish emulsion at half strength.
  • Common pest enemies are aphids, flea beetles, cabbage root maggots, cabbage worms, cabbage loopers, and wireworms. Protect the seedlings from pests and cold temperatures for two to three weeks after planting with spun poly-row covers.

Interplanting: Plant radish with bush beans, beets, carrots, cucumbers, lettuce, peas, peppers, and spinach.

Container Growing Radish: Grow in a container at least 4 inches (10 cm) deep; plant in concentric circles.

Radish sprouts

Radish planting calendar

Planting for spring harvest:

  • 4-6 weeks before the last frost in spring: direct-sow in a plastic tunnel or cold frame.
  • 4 weeks before the last frost in spring: direct-sow in the garden; minimum soil temperature 40°
  • Every 2 to 3 weeks sow succession crops.

Planting for fall harvest:

  • 8-10 weeks before the first frost in fall: direct-sow in the garden.
  • 2-4 weeks before the first frost in fall: direct-sow in the garden in a plastic tunnel or cold frame.

Radish seed sowing dates

(These dates are for the Northern Hemisphere)

Average date of the last frostPlanting dates
Jan. 20Jan. 1-Apr. 1
Feb. 8Jan. 1-Apr. 1
Feb. 18Jan. 1-Apr. 1
Feb. 28Jan. 1-Apr. 1
Mar. 10Jan. 1-Apr. 15
Mar. 20Jan. 20-May 1
Mar. 30Feb. 15-May 1
Apr. 10Mar. 1-May 1
Apr. 20Mar. 10-May 10
Apr. 30Mar. 20-May 10
May 10Apr.1-June 1
May 20Apr. 15-June 15
May 30May 1-20
June 10May 15-June 1
Radishes are ready for harvest in about 20 days
Radishes are ready for harvest in about 20 days
  • Cherry Belle’ is classic round and red.
  • ‘Easter Egg’ is multicolored.
  • ‘French Breakfast’ is long and cylindrical.
  • ‘Miyashige’ is an Asian daikon radish with long white roots.

Botanical Name: Raphanus sativus

Radish belongs to the Brassicacea (Cruciferae) or cabbage family; other members include cabbage, kale, collard, broccoli, Brussels sprouts, and turnips.

Radish articles on Harvest to Table:

How to Plant, Grow, and Harvest Radishes

Radish Seed Starting Tips

Radish Growing Problems Troubleshooting

Tasty Ways to Cook and Serve Radishes

Radish Root and Leafy Green Salad

How to Make Savory Radish-Cabbage Coleslaw

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Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.

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