Family: Asteraceae
Genus and Species: Cichorium intybus
Climate
Radicchio grows well during the cooler spring and summer months in many locations. If radicchio matures during the warmest months of summer, the leaves turn bitter. Radicchio grown in the autumn or over the winter retains its sweet flavor. In cold climates, grow radicchio in a cold frame for continual harvest throughout the cold months.
Soil
Radicchio grows well in most soils. Loose, fertile soils that have plenty of nutrients and good drainage are ideal for growing radicchio. Radicchio grows well in containers, pots, or raised beds. Grow radicchio interspersed between other plants in your garden. Radicchio's red leaves are very showy and it grows well under the leaves of other plants in partial shade. Radicchio grows best in soils with a pH of 5.5-6.8.
Spacing
Radicchio plants should be spaced 8" apart in all directions.
Direct Seeding
Direct seed radicchio outside in successive plantings for the most practical crop. Successive seedings of radicchio ensures a continual harvest rather than a huge harvest all at once. Sow radicchio seeds every two weeks from midsummer through autumn or direct seed radicchio into prepared beds as soon as the soil can be worked in the spring. Prepare the bed and rake it for a smooth finish, sow 1-2 radicchio seeds every 4", 1/4" deep in rows 8" apart. Thin plants within a row to every 8" once they are established. Space beds at 12"-18" apart.
Seeding For Transplants
Radicchio can be started in open flats or in cell packs 8 weeks before the last frost. Sow radicchio seeds in moist growing mix and thin to 1 plant every 2" once seedlings have sprouted the first set of true leaves.
Germination
These seeds germinate best in soils around 60°F-65°F.
Germination will take 5-7 days.
Transplanting Into the Garden
Transplant radicchio starts to the garden when they are 4" tall. Make sure the soil is moist and the radicchio seedlings do not dry out during transplanting. Water the radicchio seedlings well until they are firmly established.
Watering
Keep radicchio evenly moist for the most tender leaves. Radicchio leaves that are stressed due to water shortage will turn bitter and taste terrible.
Harvesting
Head Varieties: Radicchio heads are mature when the heads are firm and plump.
Leaf Varieties: Radicchio leaves can be harvested anytime after the leaves beging to open.
Head Varieties: Cut the whole radicchio head off the plant just above the soil line.
Leaf Varieties: Harvest the outer radicchio leaves as you want them. Harvest and disgard any older leaves as well.
Post-Harvest Handling
Clean the radicchio of dirt and cool using hydro cooling. Hydro cooling is the process of spraying or immersing vegetables in chilled water. Dry radicchio thoroughly before storage.
Storage
Radicchio is highly perishable and deteriorates rapidly with increasing temperature. Radicchio can be stored at 32° for 2 to 3 weeks at 98%-100%.
Radicchio is very sensitive to ethylene gas so do not store radicchio with vegetables and fruits that give off ethylene gas such as apples and pears.
Diseases
Radicchio is relatively disease free.
Pests
Radicchio is relatively pest free.
Comments
Older varieties of radicchio need to be cut back before the head forms.
References
Johnny's Selected Seeds (2002), "Radicchio", Johnny's Selected Seeds.
Oregon State University, Radicchio , Commercial Vegetable Production Guides, Last modified 2003-01-03, http://oregonstate.edu/Dept/NWREC/radicch.html, Accessed 2003-7-13
Smith, E.C. (2000), The vegetable gardener's bible: discover Ed's high yield W-O-R-D system for all North American gardening regions., Storey Books: Pownal, VT.