Before World War II more than half the crimson clover seed used in the United States was imported, principally from Hungary and France. Since 1938 domestic production has rapidly increased, reaching more than 18 million pounds in 1942. Tennessee produced more than half the home supply. Nearly all the crimson clover may be called common crimson clover, since it does not represent strains or varieties having special characteristics. White-flower strains and several others that differ slightly in maturity have been selected but have not been used.