Cumulative upkeep
(At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
If tapped for mana, Plains produce
, Islands produce
, Swamps produce
, Mountains produce
, and Forests produce
instead of any other type.
If a land has more than one basic land type, the player tapping the land for mana can choose to produce mana of either color. But if it produces more than one mana, all mana is of the same color.