Once, long ago, a herald made a jest — Stuck roses upside down upon a crest. The sky became the earth — the earth the sky, And many sovereigns stared and wondered why. But some believe the herald really tried To root the roses on the better side.
A herald, in some vague long-ago court, plays a prank: he sticks roses on a coat of arms with their heads pointing down. The joke has an odd effect. Suddenly the sky looks like the ground and the ground like the sky, and the kings and queens who see it are left baffled, wondering what they've just witnessed. The speaker tells all this in a light, almost teasing tone, as if recounting a bit of court gossip.
The last two lines turn the whole thing around. Maybe it wasn't a joke at all. Maybe the herald honestly wanted to plant the roses in the "better" place, the sky, where they could grow free of the dirt. That small twist gives the poem its charm. The speaker seems amused but also quietly sympathetic, willing to believe that what looks like foolishness could be a hopeful, imaginative act. The mood is playful and a little wistful, like a fairy tale with a wink in it.