Early Summer

At the beginning of your upkeep, you can reveal the top card of your library. If that card is a green creature, you may add it to your hand. Otherwise, put it at the top of your library.
{g}{g}: Sacrifice Early Summer: Search your library for a green creature card, shuffle your library, then put it on the top of your library.
{g}{g}{g}: Untap or tap target creature.