Bloom : The Surprising Seeds of Sorrel Fallowfield by Nicola Skinner
Sorrel Fallowfield is growing up - in a REALLY surprising way... Sorrel Fallowfield is so good at being good that teachers come to her when they need help remembering the school rules - and there are LOTS.
Luckily, Sorrel doesn't have any trouble following them, until the day she discovers a faded packet of Surprising Seeds buried under a tree in her backyard. Now she's hearing voices, seeing things, experiencing an almost unstoppable urge to plant the Seeds in some very unusual places... and completely failing to win her school's competition to find The Most Obedient Child of the School.
And all that's before flowers start growing out of her head...