Last revised February 10, 2010
Red heading type radicchio. Photo credit: Alex Stone, Oregon State University
(See also file on Witloof chicory)
VARIETIES (approximately 80 days).
This group of leafy vegetables falls under the general name of chicory. Heading and non-heading types exist. The heading types may be green-leaf or red. Some red types turn red only with the onset of cool weather.
Radicchio (Italian Chicory)
Red heading types (red with white veins or Chioggia types): Chioggia, Palla Rossa, Giulio (non-bolting, for summer harvest, turns red even during hot weather), Augusto (late summer harvest), Adria (large heads), Ronette (large heads), Firebird, Milan (early, vigorous), Verona Red, Treviso (elongated, green in summer, turning red with white veins in fall) for fall or overwintering. For trial: Cleopatra (good color), Rubello F1 for late harvest.
Green heading types: Zuckerhut (dense heads like romaine lettuce), Grumolo (cold hardy for late fall or overwintering).
Radichetta (asparagus chicory): Catalogna (narrow-leaf, non-heading variety with long petioles and some red pigmentation).
Radicchio may be grown on a wide range of soil types. Loose fertile loams, and muck soils are best. Soils should provide good water holding capacity and good internal drainage, and a pH of 6.5 and above. Since a number of these items are harvested in the fall, soils should be chosen that allow harvest in moderately rainy conditions.
SEED AND SEED TREATMENT
Radicchio seed numbers approximately 25,000 per ounce. About 0.75- 0.8 lb of raw seed are used per acre in direct seeding. Two to 3 ounces are needed per acre if transplants are used. Use a fungicide treated seed whenever possible. Have germination checked before planting if germination value is not known or current. Pelletizing seed allows precision planting.
Radicchio performs best under cool temperatures and is therefore grown in early spring or late fall. Varieties are available for summer (July and August) harvest. Red leaf Radicchio develops its best color, and grows best under cool fall or spring temperatures, however some varieties (see above) can be grown in Western Oregon and Washington throughout the summer.
Plant as early in the spring as possible and stagger plantings once or twice per week, planting only what can be harvested and sold during that interval.
Transplant only for the earliest crops. Grow transplants 4-6 weeks prior to the time they are needed using modular trays, allowing l to l l/2 square inches per plant.
Rows should be 15-18 inches. Plants should be 8 - 12 inches apart in the row depending on cultivar and crop being grown.
For the most current advice, see Nutrient Management for Sustainable Vegetable Cropping Systems in Western Oregon, available as a free download from the OSU Extension Catalog
Nitrogen: 100-150 (N) lb/acre - should be split in 2 applications.
Phosphorus: 100-150 (P2O5) lb/acre - apply all at time of seeding or transplanting, preferably banded 2 inches to the side and 2 inches below the seed or plant roots.
Potassium: 50-150 (K2O) lb/acre - broadcast prior to planting.
Sulfur: 20-30 (S) lb/acre - broadcast prior to planting.
These recommendations are intended to provide adequate fertilizer. Nitrogen rates especially may need to be adjusted depending on crop, planting date, weather conditions and soil type.
This crop requires a uniform supply of water for tender growth. Frequent irrigations are preferred because these crops are shallow rooted. A total of 8-12 inches of water may be necessary depending on crop, seasonal variation, variety, and planting date.
Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils need more frequent water applications, but less water applied per application.
HARVESTING, HANDLING, AND STORAGE
The University of California-Davis has a file on Minimal Processing of Fresh Vegetables that discusses film wrapping and other topics.
Radicchio may yield approximately 800 to 1,300 10-lb cartons per acre. Harvest is usually done by hand, and packed into cartons in the field. Keep the heads clean and free of soil and mud. Ideally, radicchio has a spicy and mildly bitter taste. A strong bitter taste, and toughness, develops if harvest is delayed or if crop is over-mature, and then the product become unmarketable.
Specialty leaf lettuces, spinach, and mustards for bag mixes have usually been harvested by hand, but harvesters for this use are now available. Three are:
Green Crop Harvester, made in England. Sole US distributors are C. and K. Anderson, Fresh Herb Co., 4114 Oxford Rd., Longmont, CO. The cost is $20,000 (1998 prices) for a 4-foot wide model which hold the greens upright by chain-driven sweeps and cuts the greens with a reciprocating knife (like a hedge trimmer). A picture of the machine can be seen in Johnny's Select Seeds 1998 catalogue, page 87.
Quick Cut harvester, an Italian, battery-powered, walk-behind machine with a 39", 48" or 54"-wide head and a band-saw cutter. Cost is $11,000. Sold by Ferrari Tractor CIE, PO Box 1045, Gridley, CA 95948; and by David Washburn and Meg Anderson of Red Cardinal Farm, 9694 75th St. North, Stillwater, MN 55082.
Enha Pro, a human-powered machine designed by Norbert Hufnagl, Field of Dreams, 117 Fredon Springdale Rd., Newton, NJ 07860. Cost is $2,429 for a two-head unit and $2,966 for a three-head unit.
Leafy items are extremely perishable and needs to be handled delicately, and marketed rapidly. If the plants are wet with rain or dew the leaves are more brittle and break more easily. Leave a few undamaged wrapper leaves on each head. Grade heads according to size, pack in cartons.
STORAGE (modified from the section on lettuce, quoted from USDA Ag. Handbook #66):
Hold radicchio at 32 F and 98 to 100 % relative humidity. Radicchio should be precooled to 34 F soon after harvest and stored at 32F and 98 to 100% relative humidity for retention of quality and shelf life. Precooling is best done by vacuum cooling because it is more effective and rapid than hydrocooling. Also, since most radicchio is field packed in corrugated cartons, vacuum cooling is more suitable. For vacuum cooling, containers and film wraps should be perforated or readily permeable to water vapor. To aid vacuum cooling, clean water may be sprinkled on the heads of radicchio prior to carton closure if they are dry and warmer than 75 F.
Radicchio is highly perishable and deteriorates rapidly with increasing temperature, and as the respiration rate increases, storage life decreases. At 32 F, radicchio can be held in good condition for 2 to 3 weeks, the time period depending on maturity, quality, and handling condition of the radicchio at harvest. The storage life at 38 F is only about half at that at 32 F.
Radicchio should be held at high relative humidity, 98 to 100%. Film liners or individual polyethylene head wraps are desirable for attaining high relative humidity; however they should be perforated or be permeable to maintain a non-injurious atmosphere and to avoid 100 % relative humidity on removal from storage.
All these crops are packaged in cartons containing 10-20 lb depending on the item. Consult buyers for preferred packaging, and container sizes.