If you take it literally, there are people that don't want the narrator and the girl together, so the narrator kills them and buries them in the garden ("fertilize the roses" "death will grow my jasmine" "buried by the lilies" "buried by the daisies"). They dance in the garden, and the narrator gets pleasure out of the fact that those that he now has the girl, the garden, and no opposition to their love.
He's a killer, but he still wants to be a prince( or the tallest man) to the girl. ("ain't no frog kissing your hand" is like the fairy tale of the frog turning into a prince, so he's already the prince)
If you take it literally, there are people that don't want the narrator and the girl together, so the narrator kills them and buries them in the garden ("fertilize the roses" "death will grow my jasmine" "buried by the lilies" "buried by the daisies"). They dance in the garden, and the narrator gets pleasure out of the fact that those that he now has the girl, the garden, and no opposition to their love.
He's a killer, but he still wants to be a prince( or the tallest man) to the girl. ("ain't no frog kissing your hand" is like the fairy tale of the frog turning into a prince, so he's already the prince)