Chicory is a bitter-tasting, leafy vegetable. There are three different types: ‘forcing’ chicory, red chicory or radicchio and ‘non-forcing’ chicory. To force chicory you need a ‘forcing’ chicory, such as ‘Witloof’.
To produce pale, crisp heads of tightly packed leaves, chicory needs to be forced into growth with the light excluded. This will also prevent them from tasting bitter.