 Lettuce 's native range spreads from the Mediterranean to Siberia , although it has been transported to almost all areas of the world . Plants generally have a height and spread of 6 to 12 inches ( 15 to 30 cm ) . The leaves are colorful , mainly in the green and red color spectrums , with some variegated varieties . There are also a few varieties with yellow , gold or blue @-@ teal leaves . Lettuces have a wide range of shapes and textures , from the dense heads of the iceberg type to the notched , scalloped , frilly or <unk> leaves of leaf varieties . Lettuce plants have a root system that includes a main taproot and smaller secondary roots . Some varieties , especially those found in the United States and Western Europe , have long , narrow taproots and a small set of secondary roots . Longer taproots and more extensive secondary systems are found in varieties from Asia . 
