This will see use in any format where it can be played alongside Immaculate Magistrate . In Standard you have Hunger of the Howlpack and Blessings of Nature . Battlegrowth may not be the highest rated card but when used on this it pays for itself. Also, Primal Cocoon ramps counters every turn. Adding to the genius is the fact you won't want to attack or block with this as long as you're using it to ramp mana. And the RTR block also gives us Golgari's Scavengers. Scavenge a couple Slitherhead s onto this and you have instant mana ramp.
Ring of Kalonia can also be used to place counters on this. You know, the farther RTR block proceeds, the more use I see for the Rings.
Well...no, actually, technically the real best manadork of all time is a three drop , but that's not even green.
Back on topic: this card is kinda bad. Play it turn 2 and...find yourself unable to use it for ramp turn 3. Or play it as an aggressive threat which can get big...except there's already a 1 drop evolve creature in green that regenerates and starts with the same power so....
Oh, Urza block... Still, though, none of those are very good in this standard environment. Cobra without fetches? Titania without legacy elves? Rofellos would probably be played with shocklands about, but he is a rare from urza...
My Seton krosan protector druid edh is happy for this.
When playing Commander, before you add a card to your deck, you have to ask yourself: "Is this card better than Rings ?" If you play commander and don't have your deck[s] in the Decklist Compendium, maybe you should. Or if you're new or looking into the format, the compendium has some good advice for beginners as well as decklists.