Tenacious Slithervine

At the beginning of your upkeep, put an
overgrowth counter on target land. That land is a Forest for as long as it has an overgrowth counter
on it.
Tenacious Slithervine gets +1/+1 for each land
with an overgrowth counter on it.
Sacrifice three Forests: Return Tenacious Slithervine from your graveyard to the battlefield.