A Late Walk

1 When I go up through the mowing field,
2 The headless aftermath,
3 Smooth-laid like thatch with the heavy dew,
4 Half closes the garden path.

5 And when I come to the garden ground,
6 The whir of sober birds
7 Up from the tangle of withered weeds
8 Is sadder than any words

9 A tree beside the wall stands bare,
10 But a leaf that lingered brown,
11 Disturbed, I doubt not, by my thought,
12 Comes softly rattling down.

13 I end not far from my going forth
14 By picking the faded blue
15 Of the last remaining aster flower
16 To carry again to you.

If the speaker feels that his life is nearing an end, what most strongly makes that argument?