Cichorium intybus is a member of the Asteraceae (sunflower) family.
Varieties include non-forcing types: Palla Rossa (popular in the US, dark green exterior leaves and a head with elongated red leaves and pure white ribs), Castelfranco (a semi-heading variety with a loose red-white inner head surrounded by green leaves streaked with rose, pink, green, or bronze in cold weather. Milder flavor, more heat resistant; Castelfranco Variegata has striped red and yellow crumpled foliage), Chioggia (variegated red and white and forms a tighter head than Castelfranco), Giulio (round, compact, red heads with very good color; it's resistant to bolting) and Cesare; forcing types: Red Verona (forms deep red, small heads with flavorful bite at maturity), and Treviso (resembles a small romaine with long, conical red heads with white midribs and crisp, tangy leaves).

Radicchio is a red, broad leaf, heading form of chicory. It has burgundy red-colored leaves with white midribs. There are numerous cultivars, some forming loose heads and others with the leaves folded in such a manner as to resemble a small head of cabbage. Leaf texture is similar to but stockier than that of a French endive. The red coloration improves during the colder months.

The first growth of many radicchios is green. These leaves are tough and very bitter. When cut back in the fall, if the weather is cold, the second growth will be bright red or magenta.

Use. The radicchio is a popular European salad vegetable and garnish produced largely in Italy. It has a distinctive, bitter flavor. Used raw the flavor and color add zest to salads.

Americans prefer to use the bitter-tasting leaves sparingly, whereas the Italians of the radicchio-growing regions of Treviso and Venice eat salads composed solely of red chicory and a vinaigrette. In Italy, there are at least fifteen 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 makes a colorful garnish.

Flowers are edible, with a faint chicory flavor. They must be used immediately after picking, because they remain open only in the morning hours.

Propagation and care. Cultural practices are similar to those of 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 September through March. In Salinas, Radicchio is grown on the standard 40 inch bed with a 22-24 inch bed top. There are two rows 12-14 inches apart on each bed. Down the row, spacing is 10-15 inches depending on the stand before thinning. Raw seed can be precision seeded with vacuum type seeders but other precision seeders require coated seed. The tops will withstand frost and low temperatures (20° F) for short periods. Some radicchio has been transplanted using module or plug type transplants.

In the warmer inland valleys the summer heat can cause bolting and tip burning and August-September plantings are recommended. It is advisable to experiment with the planting dates of the various varieties to determine the best planting date for each variety. Some varieties perform best on lighter well drained soils. In the Salinas area the crop can be seeded during the summer (March-August) if adapted varieties are used.

Harvest rates are low. Sometimes in the 20-40 percent range.

There are forcing and non-forcing types of radicchio. The non-forcing types form a head under normal growing conditions. The forcing varieties require freezing weather. The plants may be forced in one of three ways. 1) Cut the leaves off to within one inch of the crown 2 to 3 weeks before the first frost then dig the roots and store them in a burlap bag in a cool dark place (45° to 55° F). They will then produce a second growth of pale red heads. 2) Leave the plants in the ground and cover with straw or another mulch. 3) Leave the plants in the ground and let the frost kill the outer green leaves. When the dead outer leaves are peeled back the red head will be found inside.

Radicchio may be a host for lettuce mosiac. In counties, such as Monterey, which have a lettuce free period for mosiac control, radicchio is also subject to this crop free period.

Harvest and postharvest practices. USDA storage recommendations are 32° to 34°F (0° to 1°C) at 95 to 100 percent relative humidity, with an approximate storage life of 2 to 3 weeks.

Seed:
Abundant Life Seed Foundation, PO Box 772, Port Townsend, WA 98368.

Bountiful Gardens, 5798 Ridgewood Road, Willits, CA 95490.

W. Atlee Burpee & Co., 300 Park Avenue, Warminster, PA 18974.

California Gardeners Seed Co., 904 Silver Spur Road, Suite 414, Rolling Hills Estates, CA 90274.

Comstock, Ferre & Co., 263 Main St., Wethersfield, CT 06109.

The Cook's Garden, PO Box 65, Loondonderry, VT 05148.

Gleckler's Seedsmen, Metamora, OH 43540.

Heirloom Garden Seeds, PO Box 138, Guerneville, CA 95446.

Johnny's Selected Seeds, 299 Foss hill Rd., Albion, ME 04910.

Lagomarsino Seeds, Inc., 5675-A Power Inn Road, Sacramento, CA 95824.

Le Champion Heritage Seeds, PO Box 1602, Freedom, CA 95019.

Le Jardin du Gourmet, PO Box 75, St. Johnsburry Center, VT 05863.

Nichols Garden Nursery, 1190 North Pacific Highway, Albany, OR 97321.

Park Seed Co., Cokesbury Road, Greenwood, SC 29647-0001.

Pinetree Garden Seeds, Route 100, New Gloucester, ME 04260.

Redwood City Seed Co., PO Box 361, Redwood City, CA 94064.

Seeds Blum, Idaho City Stage, Boise, ID 83706

Shepard's Garden Seeds, 30 Irene Street, Torrington, CT 06790.

Taylor's Herb Gardens, 1525 Lone Oak Road, Vista, CA 92084.
Thompson & Morgan, PO Box 1308, Jackson, NJ 08527.

Vermont Bean Seed Co., Garden Lane, Fair Haven, VT 05743

More information:
Kline, Roger. "Special Vegetables." Country Journal, pp 28-32. April 1987.

Compiled by Claudia Myers, UC Small Farm Center.

Reviewed by Richard Smith, Farm Advisor, San Benito County, 12/22/89.

Reviewed by John Inman, Farm Advisor, Monterey County, 12/22/89.

Reviewed by Yvonne Savio, Freelance Garden Writer, Davis, CA. 12/27/89.

Captions:

Figure 1. Young radicchio growing in the field. (Photo by Erin Chapman)

Figure 2. Mature radicchio in the field. (Photo by Charlotte Glenn)

Figure 3. Mature radicchio with the leaves peeled back. (Photo by Charlotte Glenn)

4/30/90