Way to many variables to accurately judge this card. Unless they print a 1 mana spell/minion to summon a treant, this isn't a turn 2 play unless you are desperate. We have to see all the other cards that summon treants + the legendary spell first.
Living mana counts so Could be fairly easiy to use. Biology project could also be pretty good with living mana.
I never got any Living Mana cards and haven't crafted them, but hell, I might have to just for fun. Turn 1, Biology Project->Wild Growth. Turn 2 Living Mana. Turn 3, proceed to hit face until they clear the board and give you mana back, then play the new Mulch Giant.
This will obviously be for some type of token Druid and I think it will be fairly strong. Discover has already been proven to be an OP ability and it gives Druid a spell reload possibility. They can now add an additional Soul of the Forest, Power of the Wild or any other token buffing/creating card that helps them reload against heavy clear spell Control decks.