just an idea to be more distinguishable from wheat and barley
young corn is light green in color.
adolescent corn is darker green colored.
premature corn has brown blossoms at the top of the plant.
ripe corn has additionall yellowish green corncobs in the middle of the plant
overaged corn is getting greyish yellow.
plants may be a big taller from my point of view as well. As we don't need to keep scale with the buildings. (corn can be as high as 3 to 4 m in real life)
Anyway thanks for your efforts to make scalable graphics