In the article, Has the Green dream wilted? , the BBC news site has an interesting article on the state of green parties and politics in Europe.  My favorite quote:

For Prof Kleinert, being out of power gives greens a
chance to rethink their allegiances, including the possibility of
entering coalitions with centre-right parties like Germany’s CDU.

It could be a divisive debate, as "the feeling of the
Greens’ leaders is surely more to the middle, but the feeling of the
base is more left-wing".