Some plants are dwarfs and never will reach knee high by the Fourth of July of any year. There are more than 20 different dwarfs. Some leaves are thin, some thick. Some leaves have yellow stripes,some white. Some leaves are smooth, some wrinkled.
Some plants are dark green, some light green.
Some plants contain more protein or oil than others. Some have the male sterility characteristic. Some leaves are waxed, some are not. Some plants mature early, some late. Some genetic strains don't even produce ears of corn.