>>96230113
Roiling Regrowth lets you sac a tapped land for its cost, and as an instant you can do this at the end of your opponents turn to have 2 basics come into play untapped. It also fills up your graveyard with lands, which green now has a myriad of ways to exploit. Worst case scenario is you sit on 3 mana for a turn order and sac a land you used to pay for the cost to put two basics out just before your next turn. Harrow is slightly better since they don't come in tapped meaning you don't have to sit on mana. They're both good landfill/ramp cards that help thin your deck.