How to grow Radicchio

Where to plant

Grow radicchio in full sun in loose, fertile soil that holds moisture but drains well. Oregon State suggests a pH of about 6.5 or above. Cool weather is the key: red radicchio develops its best color and heads best in the cool of fall or early spring. Hot weather makes it bolt or stay loose and very bitter.

Some radicchio needs cool temperatures to form a head at all, so many gardeners leave plants in the ground past the first frost.

• Florida and the Gulf Coast: sow from fall into late winter, so heads mature in the coolest months.
• Texas, the Desert Southwest and Southern California: sow in early fall and again in late winter.
• Mid-South, Mid-Atlantic and Southern Plains: sow in late winter for a spring crop, and in late summer for fall heads, which are usually better.
• Northeast, Midwest, Mountain West, Northern Plains and the Pacific Northwest: sow in early spring, or better, in July for heads in fall. In the Pacific Northwest some varieties grow through summer.
• Northern California and Hawaii: a long cool-season window from fall to early spring.
• Alaska: sow from May to July in the cool summer.

Choosing a variety

• Chioggia types such as Palla Rossa and Chioggia form round red heads with white veins. Giulio resists bolting and colors red even in hot weather, so it suits a summer harvest.
• Treviso types grow upright, elongated heads that stay green in summer and turn red with white veins in fall. They suit fall harvest and overwintering.
• Green heading chicories such as Zuckerhut (sugarloaf) form dense, romaine-like heads, and Grumolo is very cold hardy for late fall.

How to plant

1. Sow seed about 1/4 inch deep directly in the bed, or start transplants for the earliest spring crop.
2. Keep the surface moist until seedlings emerge, which can be slow in hot soil in midsummer.
3. Thin or transplant to about 8 to 12 inches apart.
4. Mulch to keep the soil cool and evenly moist.

Watering and feeding

Keep the soil evenly moist. Dry spells make the leaves tougher and more bitter and can cause tipburn on the inner leaves.

Radicchio needs only moderate feeding. Work compost into the bed before sowing; too much nitrogen gives large, loose plants.

Pruning and care through the year

• Many radicchios first grow a loose rosette of green, tough, very bitter leaves. If you cut these back in early fall, leaving the crown, the regrowth in cold weather forms the red, tender head.
• Remove any rotting outer leaves in wet weather to keep bottom rot from spreading into the head.

Harvesting

Cut heads at the base once they feel firm and have colored up, usually after some cool nights. Light frost improves flavor, and in mild areas heads can be cut through winter. A cut stump may regrow a few small heads or leaves.

Whole heads keep in the fridge for about two weeks.

Growing in pots

Radicchio grows well in a pot or trough at least 8 inches deep with a good potting mix. Keep it watered and in a cool, sunny spot.

Using it

Slice raw radicchio into salads with something sweet or rich, such as citrus, pears, nuts or cheese, or grill or roast halved heads, which mellows the bitterness.

Forcing

For blanched heads, dig mature plants in late fall, cut off the leaves, and replant the roots in moist peat or soil in a dark, cool place such as a basement, covered with a bucket. Pale, tender, bittersweet shoots grow from the roots over a few weeks.