Regrowth in the cool weather promotes head and color formation. Verona has short round leaves and develops good color. Treviso forms a more tapered head due to its long. Most seed sources showed wide variation in plant types. The exception was Augusto variety from Jonnnys' with excellent early color and heading.
Leaves are most tender and delicious inside the heads.
Radicchio is sensitive to the rigors of being overwintered. Covering with a cloche will help to make a spring harvest possible. Also. if transplanted very early, a harvest might be possible before heat causes flowering. At that stage you will see the exacting similarity between this delicious and coveted garden plant and the blue-flowered, roadside weed. Where lettuce performs poorly in midsummer.