How to Grow Radicchio from Seed

Radicchio grows best in the cool weather of spring and fall.

Radicchio has a lettuce-like head that colors to a deep rosy red as the weather grows cold in autumn or winter. The slightly bitter taste of radicchio sweetens with cooler day temperatures.

When to Plant Radicchio

Direct seed radicchio in the spring as soon as the soil can be worked or start seed indoors 8 weeks before the last frost in spring protected by a plastic tunnel.
Seeds germinate quickly even in cold soil and light frost will not harm the seedlings.
Avoid growing radicchio during the summer. Warm temperatures cause radicchio leaves to become bitter and pungent.
Radicchio matures in 75 to 110 days depending on the variety.

Radicchio Sowing and Planting Tips

Radicchio can be grown from seeds or transplants.
The seed is viable for 5 years.
Start indoors 12 to 8 weeks before the last frost or sow; transplant maturing seedlings into the garden 2 weeks before the last frost. Or direct-sow seed in late summer for autumn or winter harvest.
The optimal growing air temperature for radicchio is 45°-65°F (7-18°C).
Sow seed ¼ inch (6 mm) deep.
Sow seeds 2 inches (5 cm) apart; later thin seedlings 8 to 10 inches (20-25 cm) apart. Make sure there is good air circulation around maturing plants to avoid disease.
For intensive planting space plant 8 inches (20 cm) apart in a staggered pattern.
Radicchio grows best in full sun but can tolerate light shade.
Prefers a soil pH between 5.0 and 6.8.
Seed germinates in 5 to 7 days at or near 60°F (7°C)—but sometimes seed can take up to 2 weeks to germinate if the soil is cold.
Keep the soil evenly moist until seeds germinate then keep the soil moist until seedlings are well established.
Add aged compost to planting beds in advance of sowing; compost will feed the soil and aide moisture retention.
Avoid planting radicchio where endive and escarole have recently grown.
Make successive sowings every few weeks for an extended harvest.
Fertilize with an organic fertilizer such as fish emulsion at half strength.
Aphids, flea beetle, leafhoppers, armyworms, snails, and slugs can attack radicchio.

Interplanting Radicchio

Interplant radicchio with lettuce.

Container Growing Radicchio

Grow radicchio in a container at least 12 inches (30 cm) wide and deep.

Radicchio Recommended Planting Calendar

8 weeks before the last frost in spring: direct-sow in a plastic tunnel or cold frame.
8 weeks before the last frost in spring: start seed indoors for transplanting later.
2 weeks before the last frost in spring: direct sow in the garden.

For Fall Harvest and Winter Harvest:

6-5 weeks before the first frost in fall: direct-sow in the garden for a fall crop.
5-3 weeks before the first frost in fall: direct-sow in a plastic tunnel or cold frame for winter harvest.