Radicchio: Specialty Crop
Excerpted from the Small Farm Program'sSpecialty and Minor Crops Handbook
Cichorium intybus is a member of the Asteraceae (sunflower) family. Radicchio varieties include "forcing" and "nonforcing" types. Forcing types are Red Verona (small, deep red head with flavorful bite at maturity) and Treviso (resembling a small romaine lettuce, with a long, conical red head with white midribs and crisp, tangy leaves).
Nonforcing types include Palla Rossa (popular in the United States; dark green exterior leaves, and a head with elongated red leaves and pure white ribs), Castelfranco (semi-heading variety with a loose red and white inner head surrounded by green leaves streaked with rose, pink, green, or bronze in cold weather; milder flavor, more heat resistant); Castelfranco Variegata (crumpled foliage is striped red and yellow), Chioggia (variegated red and white; tighter head than Castelfranco), Giulio (round, compact, red head with very good color; resists bolting), and Cesare. Radicchio is a red, broadleaf, heading form of chicory. Its leaf colors range from pink to maroon with white midribs; variegations include bronze and almost yellow streaks with green.
Some cultivars form loose heads, while others have folded leaves and resemble small cabbages. Leaf texture is similar to but stockier than that of a French endive. The red coloration increases during the colder months. The first growth of many radicchios is green. The green leaves are tough and very bitter. If these leaves are cut back in fall and the winter is cold, the second growth will be bright red or magenta.
Radicchio is a popular European salad vegetable and garnish produced largely in Italy. It has a distinctive, bitter flavor, and is eaten raw or lightly grilled or roasted. Its flavor and color add zest to salads and other dishes. Americans prefer to use the bitter-tasting leaves sparingly. In Italy, there are at least 15 well-known kinds, from the flat, dark rosettes of Ceriolo to the long, thin leaves of Selvatico da campo to the variegated pink and pale green of Castelfranco. Radicchio also serves as a colorful garnish. The edible flowers have a faint chicory flavor. They must be used immediately after picking, since they remain open only in the morning hours.
Propagation and care
Cultural practices are similar to those for endive, escarole, and lettuce, but radicchio requires a longer growing period than lettuce (80 to 85 days in the Salinas Valley) and so may require an extra irrigation. Sow seeds 1/4 to 1/2 inch deep from September through March. In Salinas, radicchio grows on a standard 40-inch bed with a 22 to 24 inch bed top. Two rows grow 12 to 14 inches apart on each bed. Down the row, plants grow every 10 to 15 inches depending on the stand before thinning. Raw seed can be precision seeded with a vacuum-type seeder, but other precision seeders require coated seed. The tops will withstand frost and low temperatures (to 20ûF) for short periods. Some radicchio has been transplanted using transplanting modules or plugs.
In the warmer inland valleys, the summer heat can cause bolting and tip burning, so August and September plantings are recommended. Growers should experiment to determine the best planting date for each variety. Some varieties perform best on lighter, better-drained soils. In the Salinas area growers can seed the crop during the summer (March to August) if they use adapted varieties. Harvest rates are low, sometimes in the 20 to 40 percent range. Many of the plants will produce either unmarketable heads or no heads at all.
As previously mentioned, there are two types of radicchio: "forcing" and "nonforcing." Nonforcing radicchio forms a head under normal growing conditions, whereas a forcing variety will form a head only after freezing weather. There are three ways to force radicchio to form a head: (1) cut the leaves off to within 1 inch of the crown 2 to 3 weeks before the first frost, and then dig the roots and store them in a burlap bag in a cool dark place (45 degrees to 55 degrees F) where they will produce a second growth of pale red heads; (2) leave the plants in the ground and cover them with straw or another mulch; or (3) leave the plants in the ground and let the frost kill the outer green leaves. Upon peeling back the dead outer leaves, you will find the red head inside.
Radicchio may be a host for lettuce mosaic. In counties like Monterey that enforce a lettuce-free period for mosaic control, radicchio is also subject to this crop-free period.
Harvest and Postharvest Practices
The USDA storage recommendation is 32 degrees to 34 degrees F at 95 to 100 percent relative humidity, with an approximate storage life of 2 to 3 weeks.
Radicchio Seed SourcesAbundant Life Seed Foundation
P.O. Box 772, Port Townsend, WA 98368
5798 Ridgewood Road
Willits, CA 95490
W. Atlee Burpee and Co.
300 Park Avenue
Warminster, PA 18974
Comstock, Ferre and Co.
263 Main Street
Wethersfield, CT 06109
The Cook's Garden
P.O. Box 65
Londonderry, VT 05148
Johnny's Selected Seeds
299 Foss Hill Road
Albion, ME 04910
Le Jardin du Gourmet
P.O. Box 75
St. Johnsbury Center, VT 05863
Nichols Garden Nursery
1190 North Pacific Highway
Albany, OR 97321
Park Seed Co.
Greenwood, SC 29647-0001
Pinetree Garden Seeds
New Gloucester, ME 04260
Redwood City Seed Co.
P.O. Box 361
Redwood City, CA 94064
Shepherd's Garden Seeds
30 Irene Street
Torrington, CT 06790
More Radicchio Information
Chandoha, Walter. 1984. Grow Italian greens-radicchio, escarole, and arugula. Organic Gardening, 31(5):80-84.
Eagle Research and Development Inc. 1984. Radicchio, a salad crop new to the United States. Eagle Research and Development Inc., Salinas, CA.
Glenn, Charlotte, and Georgeanne Brennan. 1988. Le Marche Seeds International spring Ô88 catalog. L Marche Seeds International, Dixon, CA.
Kline, Roger. 1987. Special vegetables. Country Journal, April 1987.
Larkcom, Joy. 1986. Radicchio. Gardening Magazine. April 1986.
Mansour, N. S. 1990. Radicchio. Vegetable Crops Recommendations. Oregon State University, Corvallis, OR.
Stephens, James. Minor vegetables. 1988. Cooperative Extension Bulletin SP-40, University of Florida, Gainesville, FL.
Whealy, Kent. 1988. Garden seed inventory, 2d ed. Seed Saver Publications, Decorah, IA.
USDA. 1987. Tropical products transport handbook. Agric. Handb. 668. USDA, Washington, DC.
Prepared by Yvonne Savio, John Inman, and Claudia Myers.