For example, when rice grows to the seventh leaf, it is called seven-leaf age. Another example is corn, which has six leaves, five of which are ripe and the top one is not finished yet. At this time, we can roughly measure the size of the top leaf below and the leaves below it. If they are the same size, we can be sure that the leaves are mature and the corn is 6 leaves old. If it is only half the size of the leaves below it, it can be determined that the leaf age of this corn is 5.5. If it is three-quarters as big as the leaves below it, then the leaf age can be considered as 5.7.