Encourage students to think like a poet:
Writing poems about flowers? Take a walk outside. Observe. Really look at "a bunch of flowers," then compare them to something else, conjure up a new image, a fresh metaphor, for instance:
A party of pansies
A meeting of marigolds
A parade of daisies
Think about the exact right word.
Think of sound and sense; observe and use fresh images.
Play with metaphors (the sky is a blue sheet ... ) and personification (waving in the wind) and simile (the sky is like a blue sheet, waving in the wind).