When a girl is revived from cryo-stasis she is told how trees hold power over the world, even going as far as controlling how much water is made available. This convenient explanation fills us in on the back story and explains the reasoning behind the incredibly impressive opening sequence. And it really is impressive, the dramatic music and the slick animation show the advancing of the plants from the moon, burning through the Earth's atmosphere - an event which eventually led to the dystopia we see on screen.
The age of technology has passed and humanity exists against a ravaged backdrop of ruined cities. A blend of hand-drawn and computer animation work well, and the backgrounds are beautifully drawn to give amazing detail - almost photographic in some cases!
I have seen many films which deal with forest spirits (Princess Mononoke (Special Edition)
and My Neighbour Totoro
being two studio Ghibli examples) but the idea of genetically modified plants with their own intelligence feels like a clever alternative.
The ensuing adventure/battle between those who want the trees to be obliterated and those who want harmony introduces the familiar anime themes of environmentalism, giant mecha constructions, and the desire to finish off a father's work.
In a nutshell: staggering animation with a plot which should have been better but sometimes simply dragged. I'd give this 3.5 if I could, but I can't. So I'm opting for 4. I enjoyed this, and it's a 'must watch' for anime fans, if just for the visuals alone.