Treetime by Roger Norman
Treetime is a once-in-every-hundred-years time, when trees uproot and come alive - sometimes for good, and sometimes for evil. Alone in his attic bedroom, Alan hears a scratching and a scrabbling against the window. This is Treetime, and Mister Ash is stirring because he wants revenge.A tale of suspense, magic and excitement from a master story-teller.