Radicchio 'Carmen' (Radicchio)

Radicchio can be somewhat unpredictable, so consult seed sources for best practices. The general rule-of-thumb is to plant older varieties in spring, then cut back plants by late summer to encourage head production (which should mature about 2 months later). 4 to 6 weeks before average last frost is the best time to direct-seed, although nonforcing varieties can be sown through summer for your fall and winter harvests. Plant seeds 1/4 to 1/2 inch (1/2 - 1 cm) deep, 3 - 4 inches (7 - 10 cm) apart, in rows 24 inches (60 cm) apart. Thin to 10 inch (25 cm) spacings.
4 to 6 weeks before average last frost is the best time to direct-seed, as non-forcing varieties can be sown through summer for your fall and winter harvests. Mulching helps suppress weeds and retain moisture.

Mulching crowns from harvested plants can yield you an additional harvest in spring, if conditions are mild.