In Flanders fields the poppies blow
I didn't realise for years that blow in this poem may actually mean bloom. It's the second meaning of blow hidden in every dictionary. In fact, Chambers puts it first: blow v.i. to bloom or blossom. Hence a 'full blown rose'. The poppies may not be blowing in the breeze but blossoming and blooming.
"I know a bank where the wild thyme blows" in A Midsummer Night's Dream is certainly about blooming and not bending in the breeze.
Bloom is also definitely the meaning in Milton's Lycidas:
As killing as the canker to the rose,
Or taint-worm to the weanling herds that graze,
Or frost to flow'rs, that their gay wardrobe wear,
When first the white-thorn blows;
Such, Lycidas, thy loss to shepherd's ear.
White-thorns blow in the windy sense all year round, but in the blossomy sense they blow in May or early June, after the frosts have stopped.
Bending or blossoming? A young soldier, Cyril Allinson, who was there at the composition later reported that the poppies were being blown by a gentle east wind, but he also said that McCrae handed him the poem without saying a word. For myself, I think that a flower that blows must be assumed to be blooming, unless stated otherwise, especially in the mind of former English master like McCrae who must have been at least half aware of the echo of Shakespeare's wild thyme.
Flanders Fields is the only great English example of a rondeau. As it is the anniversary of the end of the war, perhaps you should balance Flanders Fields with Siegfried Sassoon's account of the moment that peace was announced:
Everyone suddenly burst out singing;
And I was filled with such delight
As prisoned birds must find in freedom,
Winging wildly across the white
Orchards and dark-green fields; on—on—and out of sight.
Everyone’s voice was suddenly lifted;
And beauty came like the setting sun:
My heart was shaken with tears; and horror
Drifted away … O, but Everyone
Was a bird; and the song was wordless; the singing will never be done.
Update: flicking through a dictionary of quotations has given me these, putting blow as a poetic term for bloom up till 26 years before In Flanders Fields:
The budding rose above the full blown...
-Wordsworth The Prelude, Book XI 1850
Against the blown rose may they stop their nose
That kneel'd unto the buds
-Shakespeare Antony & Cleopatra II,v
The flower that once hath blown forever dies
-Edward Fitzgeral Omar Khayyam 1889
To me the meanest flower that blows can give
Thoughts that do often lie too deep for tears
-Wordsworth Intimations of Immortality
I sometimes think that never blows so red
The rose as where some buried Caesar bled
-Fitzgerald Omar Khayyam 1889
O fairest flower, no sooner blown but blasted,
Soft silken primrose fading timelessly.
-John Milton On the Death of a Fair Infant, Dying of a Cough [It wasn't the cough/That carried him off/But the coffin/They carried him off in.]