Posy and the Trouble with Draglings by Lara Faraway
The world we know is only the beginning. Beneath the surface and between the moonbeams is another, more magical realm. All magic comes from this place, through doorways that only the fairies can open. And at its centre is the Fairythorn Tree -- the oldest tree in any garden, wood or park, and home to the tiny fairies who live in its branches. When the fairies' pet draglings get scooped up by Big Alice who's pond-dipping for school, it's up to Posy to rescue the draglings before the Bigs discover what they've caught.