Corn plants are 2 blocks high, and yield corn cobs. These can be
cooked to corn-on-the-cob, or processed to make corn seed (corn
kernels, basically).
Digging a mature plant yields the corn cob. A harvested corn plant
"wilts", and needs to be dug away to make the land usable, or can
be left as ornamental 2-block plant. Digging either top or bottom
block works in all cases, although I need to verify that I've
covered every block combo.
