Sakura-Tribe Springcaller is a common Creature — Snake Shaman card from Betrayers of Kamigawa (BOK), collector number 142. Current market price: $0.19 (foil $1.53), TCGplayer market prices via Scryfall.
At the beginning of your upkeep, add {G}. Until end of turn, you don't lose this mana as steps and phases end.