How we cite our quotes: (Line)
Quote #4
O if we but knew what we do
When we delve or hew—
Hack and rack the growing green! (9-11)
Here the poem shifts from the first stanza to the second and, at the same time, it pivots to a bigger picture. We're no longer just talking about the poplars. The speaker has turned his attention to the natural world as a whole ("the growing green"). The real tragedy, then, becomes humanity's inability to see how much damage it's inflicting on the environment. Well, we're glad sure that changed completely in the last hundred years (sarcasm alert).
Quote #5
Since country is so tender
To touch, her being só slender, (12-13)
Here the speaker personifies the natural world as a "her," saying how fragile and sensitive it is. Sure, this is a pretty backward view of the "weaker sex," but Hopkins is just using the prevailing chauvinism of his time to point out how important it is to take care of our natural world.
Quote #6
Where we, even where we mean
To mend her we end her,
When we hew or delve:
After-comers cannot guess the beauty been. (16-19)
Want to "clean up" the environment? Well, too bad. You're still transforming it from unspoiled Nature into an area of human influence. Any attempts to meddle in the natural world, says that speaker, will change the nature of…Nature—forever. Anyone who comes after that moment will be unable to appreciate what was there before humanity came tromping along, ruining everything.