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.
- 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.
Radicchio Recommended Varieties
- ‘Rossa di Treviso’ and ‘Rossa de Verona’ are standards.
- ‘Giulio’ for spring crops.
- ‘Augusto’ for fall and winter crops.
Botanical Name: Cichorium intybus
Radicchio belongs to the Compositae (Asteraceae) or sunflower family.
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