Personally I think the poem "In Hardwood Groves" relates to the substitution of human generation. At the beginning of the poem, the speaker says "the same leaves over and over again" (1). Actually the leaves are different each year but they are kind of same as a whole. As for people, generations shift over and over again, they seem familiar with each other for they are all formed by human beings. Besides, the speaker expresses the idea that the old leaves decay before the new leaves grow in second stanza. "They must go down past things coming up/ they must go down into the dark decayed" (7-8) depicts the law of nature, which can be connected to human beings. Old generation is getting senile and approaching the death. "They must be pierced by flowers and put/ beneath the feet of dancing flowers" (9-10) shows that new life is growing on the died leaves. Similarly, as for people, new generations always come following the past ones. I feel like the poem talks about the cycle of human life.