We reach the climax of the series where we'll find out who is the greenest family in the whole valley.
Garden biodiversity is the green challenge and Iolo sets the children a challenge close to his own heart – to create a wildlife film in their own back garden.
Our families also promote biodiversity in the valley by doing their washing in an unusual location and by using their own power.
Iolo Williams finally gets to plant his new woodland with the children of the valley.
© 2012 S4C
O Gymru / Made in Wales