Overgrowth

Enchantment - Aura, 2G (3)
Enchant land (Target a land as you cast this. This card enters the battlefield attached to that land.)
Whenever enchanted land is tapped for mana, its controller adds {G}{G} to his or her mana pool (in addition to the mana the land produces).¹
Illus. Christopher Rush

Gatherer Card Rulings [Nov 2009]

• 10/4/2004: This is a triggered mana ability.

Format Legality	Legal in Vintage, Legacy, Extended Banned in Standard
Printings (3/24)	Tenth Edition (Common) Core Set - Ninth Edition (Common) Stronghold (Common)