All cultivated corn belongs to the same species. Within this species there are six main groups, differentiated by the type of kernel:

Each mature kernel has an indentation on the top. The dent corn plant is the largest type, reaching 8 to 15 feet (2.4-4.6 m) in height. Dent corn is the principal type grown in the United States and is widely used for feed, fodder, and silage.

Large, hard kernels grow on long, slender ears. The kernels on the same ear are often several different colors. Flint corn matures early and is grown mostly in northern states.

Each kernel is covered with a husk. This is a primitive type and is little grown.

The small, hard-hulled kernels explode when heated, turning inside out to a white, fluffy mass.

The soft kernels have a high starch content. Soft corn was widely grown by the Indians, but is no longer raised on a large scale in the United States.

The broad, tender kernels have a high sugar content. The plant is grown in the northeastern and midwestern states. It is sold canned, frozen, or fresh.

All but pod corn and popcorn have numerous varieties. They differ in size and hardiness; in resistance to disease and insects; in the size, texture, color, and hardness of the grain; and in the nutritive value of the stalk and leaves.