Indigo (F1) Radicchio Seed

Scientific name

Cichorium intybus

Growing conditions

Modern radicchio is much more reliable in North America than the old Italian strains, but heads can still vary from plant to plant and season to season. Each variety is bred for a particular season; trying two or three in staggered plantings is the surest way to learn what does well on your farm. Radicchio is hardy, can go in as soon as the ground can be worked and grows best at 60–65°F (15.5–18.3°C). It does best in spring, fall and winter; summer crops work only where nights stay below 60°F (16°C), and the variety choice matters.

Germination and heat

Seed exposed to temperatures above 77°F (25°C) can go dormant and refuse to sprout. Keep the soil cool and moist, ideally 60–68°F (15.5–20°C), for the best stand.

Days to maturity

Counted from transplanting in cool spring weather. Take off 10–14 days for warm late-spring or early-summer plantings, and add about 14 days for direct sowing.

Transplanting

Sow 3–4 weeks before planting out, about 4 seeds per inch in open flats or into 3/4" plug cells, and just cover the seed with fine vermiculite. On warm, sunny days shade the trays to keep the surface under 75°F (24°C) until the seedlings are up. Seedlings from open flats can be moved into cells or pots, 1–2" apart, about two weeks later. Harden off for 2–3 days with less water and cooler temperatures; well-hardened plants can handle 20°F (-6°C). Plant 8" apart in rows 18" apart, setting each plant a little high so the base sits just above the soil, which helps prevent bottom rot.

Direct sowing

Sow seeds 1" apart in rows 12–18" apart, cover with about 1/8" of soil and firm gently. Thin to 8" (the thinnings can be transplanted). Water dry soil to keep it cool and evenly moist for an even stand.

Succession planting

Sow every 3 weeks for a steady harvest.

Seeding rate

At 3 seeds every 8" in rows 18" apart: about 1,000 seeds per 220 ft., 5,000 per 1,100 ft. and 131,000 per acre.

Transplants

Sowing 2 seeds per cell and thinning to one gives about 500 plants per 1,000 seeds.

Packet

100 seeds.

Seeds per oz.

About 19,200 on average.