At the end of the poem the speaker asks whether he is going to sleep or dying.
The poem describes picking apples. For the speaker, picking apples is a spiritual experience. It connects him to nature, and to tradition. He is surrounded with peace, but it is still hard work. He gets tired after picking apples for so long, and decides to lie down. The speaker has become overwhelmed. Ironically, you can have too much of a good thing.
One can see what will trouble
This sleep of mine, whatever sleep it is.
Were he not gone,
The woodchuck could say whether it's like his
Long sleep, as I describe its coming on,
Or just some human sleep.
The speaker wants to know whether the “long sleep” of death is “coming on,” or if it is just “some human sleep.” He looks to nature, saying that the woodchuck could tell him again. Either way, the speaker is returning to nature by going to sleep.