Elvish Piper

{G}, {T}: You may put a creature card from your hand onto the battlefield.

Ivy Dancer

{T}: Target creature gains forestwalk until end of turn. (It can't be blocked as long as defending player controls a Forest.)

Dauntless Dourbark

Dauntless Dourbark's power and toughness are each equal to the number of Forests you control plus the number of Treefolk you control.
This creature has trample as long as you control another Treefolk.

Treefolk Seedlings

Treefolk Seedlings's toughness is equal to the number of Forests you control.

Oracle of Mul Daya

You may play an additional land on each of your turns.
Play with the top card of your library revealed.
You may play lands from the top of your library.

Treefolk Mystic

Whenever this creature blocks or becomes blocked by a creature, destroy all Auras attached to that creature.

Quickbeam, Upstart Ent

Whenever Quickbeam or another Treefolk you control enters, up to two target creatures each get +2/+2 and gain trample until end of turn.

Dungrove Elder

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Dungrove Elder's power and toughness are each equal to the number of Forests you control.

Yavimaya, Cradle of Growth

Each land is a Forest in addition to its other land types.

Fangorn, Tree Shepherd

Treefolk you control have vigilance.
Whenever one or more Treefolk you control attack, add twice that much {G}.
You don't lose unspent green mana as steps and phases end.

Generous Ent

Reach
When this creature enters, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
Forestcycling {1} ({1}, Discard this card: Search your library for a Forest card, reveal it, put it into your hand, then shuffle.)

Kalonian Twingrove

Kalonian Twingrove's power and toughness are each equal to the number of Forests you control.
When this creature enters, create a green Treefolk Warrior creature token with "This token's power and toughness are each equal to the number of Forests you control."

Ashaya, Soul of the Wild

Ashaya's power and toughness are each equal to the number of lands you control.
Nontoken creatures you control are Forest lands in addition to their other types. (They're still affected by summoning sickness.)

Treefolk Harbinger

When this creature enters, you may search your library for a Treefolk or Forest card, reveal it, then shuffle and put that card on top.