Three short scenes show a spring that hasn't quite arrived. In the first, the speaker pictures the wind with nothing to play against if the daffodils weren't there. The phrase "hoopla of blooms" makes the flowers sound like a small carnival, bright and noisy, and the question suggests the speaker is glad of them. They give the wind something to move.
The second stanza turns tense. The tree leaves are "packed tight as gunpowder in their slim cartridges," so the buds look like ammunition waiting to go off. Nothing has happened yet, but the energy is stored up.
In the last stanza, the wind carries "the rumor of a storm," and only the rhododendron reacts by turning pale. That small detail is quietly funny and a little eerie, as if the plant is the one nervous guest at the party. The mood is watchful and playful at once: the speaker pays close attention to the garden and enjoys how it seems to feel things.