Spring mix, or mesclun, was originally a mixture of arugula, baby lettuces, chervil and curly endive, but now there are many different varieties to choose from. Varieties often include a number of tender greens and baby lettuces such as red and green romaine, red oak leaf, spinach, lolla rossa, arugula, frisée, curly endive, chard and even purple radicchio. Flavors range from mild to bitter depending on the blend.