How we cite our quotes: (line)
Quote #1
This lime-tree bower my prison! (2)
You could read the beginning in at least two ways. Either the speaker views nature itself as a prison because he has a distorted perspective at the moment, or he views only that nature which has been controlled and domesticated by humans as confining.
Quote #2
They, meanwhile,
Friends, whom I never more may meet again,
On springy heath, along the hilltop edge,
Wander in gladness, and wind down, perchance,
To that still roaring dell, of which I told;
The roaring dell, o'erwooded, narrow, deep, (5-10)
It's as if he thought nature would swallow up his friends and suck them into a black hole – why else would he worry about not seeing them again? Nor do we think it's a coincidence that he imagines them traveling down into a dark ravine here.
Quote #3
Ah! slowly sink
Behind the western ridge, thou glorious Sun!
Shine in the slant beams of the sinking orb,
Ye purple heath-flowers! richlier burn, ye clouds!
Live in the yellow light, ye distant groves!
And kindle, thou blue Ocean!(33-38)
In the speaker's first attempt at union with nature, he takes kind of a bossy tone, ordering the flowers to do this and the clouds to do that. Actually, he's using an ancient rhetorical device known as apostrophe, in which the speaker demands that nature do everything it is already doing – only better. You'll find this device in a lot of Romantic lyrics.