Among the big crops in world agriculture, clover is a late-comer. From southern Spain, where it was domesticated around the year 1000, clover conquered Europe. In the 17th and 18th centuries, when European agriculture ran into a critical nitrogen deficit due to growing exports of cereals to ever-increasing numbers of populous cities, clover, which is an efficient nitrogen fixer, became essential for feeding the population. In the 19th century clover was the agricultural equivalent of coal. Just as coal-smoking chimneys changed the landscape, so did the vast, sweet-smelling white and red clover fields. The romantic 19th-century landscape was a clover landscape. And just as coal was phased out in the 20th century by other energy carriers, clover was made superfluous by the Haber-Bosch ammonia synthesis method (1909), which made possible the production of nitrogen for agriculture 'from the air' without intermediaries. The phasing out of clover contributed to the creation of the dull, post-Second World War monocultural landscape.