When a poem starts off describing the very first subject of the very first sentence as "my love," we don't have to work too hard to assume that the poem is about… love.
Horn at hip went my love riding (11)
Notice how Cummings clusters a bunch of descriptors around the "love"? There's something interesting going on with the way that the alliterative phrase "horn at hip" works, too. It seems like it should be part of an entire clause, something like "wearing a horn at her hip,…" You get the picture. But instead, Cummings cuts out all the extra language, making the resulting poem as lean as the hounds racing by the hunter's side.
All in green went my love riding (31)
Wait a second. Haven't we seen this line before? Like maybe at the very beginning of the poem? Repeating the first line in the final stanzas creates a sort of cyclical sense, as if things are going to wrap up neatly.
my heart fell dead before. (35)
This line is the first time that something in the poem isn't singing "before" the action. Instead, the heart is falling… um, dead. Why not something like "my heart sang before"? Why is the violence necessary? Well, that's part of the danger of love. As they say, it hurts.
Fleeter be they than dappled dreams (6)
Here's a funny twist to the story: although the speaker seems to concentrating on the "love" on a huge golden horse, he saves all of his loving adjectives for animals. Check out this description of the deer that the lover is ostensibly hunting.