Okay, so stanza 1:
...the flowers may rise in Spring, the trees may bud... and swaying beeches...
Up, up he went. ... At last, weary and feeling finally defeated...
Hard and cruel and bitter was the land that met his gaze... from it rose in huge columns a swirling smoke... Sam beheld Mount Doom, and the light of it... now glared against the stark rock faces, so that they seemed to be drenched with blood.
There he halted and sat down... if once he went beyond the crown of the pass and took one step veritably down into the land of Mordor, that step would be irrevocable. He could never come back.
All four are from various parts of
The Tower of Cirith Ungol, but what I can't do is tie it in to the rest of the riddle. By the time we hit ruined homes and barrows I am completely at sea.
Final thought: back in
The Stairs of Cirith Ungol, Sam directly says that "we're in the same tale still"; which could be the source of the "taking up the tale" line.
But I can't bring enough of this together to make a guess.
hS