"Poof" refers to the "cloud" of swirling pinkness around the lady's dress. "Poof" is sometimes said to be the sound made when a person or a thing "puffs". Note that it should not be mixed up with the informal/slang word "poof" referring to a male homosexual.
"Overgrown" is an adjective.
"The blast" seems to refer to the "lightning-type" criss-crossing of the trees across the canvas, but then the speaker seems to say the same thing about "the bough". I'm really not clear on this part.