My aspens dear, whose airy cages quelled, Quelled or quenched in leaves the leaping sun, All felled, felled, are all felled
We start the poem off with a little note. In the poetry business, a note that comes just after the title but before the first line is called an epigraph. And this one tells us that something was "felled" in 1879.
Here, "felled" is just another way to say "fallen." More specifically, though, the word "felled" suggests that something made something else fall.
In this case, the something that has fallen is—just checking the title here—the Binsey Poplars. We say more about them over in "What's Up With the Title?," but for now we'll just note that Binsey is a village in England not too far from Oxford, where Gerard Manley Hopkins went to college and later worked.
And a poplar is a kind of tree, something that is typically "felled" by storms, or beavers, or lumberjacks. Before we even get into line 1, then, we know that our speaker is focused on some trees that were cut down in the village of Binsey way back in 1879.
Everybody good? Great—let's get reading, then.
We start out not with poplars, but with "aspens." Um…what gives?
Of a fresh and following folded rank Not spared, not one That dandled a sandalled Shadow that swam or sank On meadow and river and wind-wandering weed-winding bank.
In these lines, we learn that the trees were arranged in a line or, as the speaker puts it, "a fresh and following folded rank."
Now, did our speaker just fall in love with F words here (the clean ones, anyway)? Maybe—you can check out "Sound Check" for more on that. Beyond that, a "rank" is a line of something, usually soldiers. The way these trees looked, standing all in a row, made it seem to the speaker as if they were following each other, almost like a military procession, practically folding into one another. The effect for him was a positive one: "fresh."
You know what's not fresh, though? All of these poor trees have been cut down. Not a single one remains. That's downright rotten, if you ask us.
The speaker breaks out some serious personification to describe the way the trees' shadows used to resemble legs with sandals on them. These shadows would dangle (or "dandle," which is pretty much the same thing) over the meadow, the river, and the riverbank—or else it seemed as though they sunk into the water or the grass.
Essentially, the speaker treats these tree shadows as figurative legs of someone who would be frolicking on the riverbank next to the meadow. They gave off a carefree, joyous vibe. After all, who wears their Sunday loafers to go hang out on the river?
To sum things up, then, our speaker really dug those trees—and he's not very happy to see them all cut down.
Before we leave this stanza, we should point out that you're not hearing things. These lines are bound pretty tightly together through Hopkins' use of both meter and rhyme scheme. We say much more about that, though, over in "Form and Meter."