Between the eye of the sun and the eyes of the tulips, (47)
Nature gives us plenty of pretty images in this poem, but it's also a bit of a threat. Its powerful forces fill the poem with life, but they also make our fragile speaker feel vulnerable and maybe even a little imprisoned.
Now the air snags and eddies round them the way a river Snags and eddies round a sunken rust-red engine. (53-54)
Here the tulips are turned into something man-made, a rusted engine stuck in a river. That's the way it goes with these tulips. They are natural, sure, but there's also something not quite right about them, like an engine that's been plunked in the middle of a beautiful river.