Unstoppable Ash

Trample
Champion a Treefolk or Warrior (When this enters, sacrifice it unless you exile another Treefolk or Warrior you control. When this leaves the battlefield, that card returns to the battlefield.)
Whenever a creature you control becomes blocked, it gets +0/+5 until end of turn.

Quickbeam, Upstart Ent

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

Ghoultree

This spell costs {1} less to cast for each creature card in your graveyard.

Orchard Warden

Whenever another Treefolk creature you control enters, you may gain life equal to that creature's toughness.

Kalonian Twingrove

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

Bosk Banneret

Treefolk spells and Shaman spells you cast cost {1} less to cast.

Reach
Whenever Six attacks, mill three cards. You may put a land card from among them into your hand.
During your turn, nonland permanent cards in your graveyard have retrace. (You may cast permanent cards from your graveyard by discarding a land card in addition to paying their other costs.)

Battlewand Oak

Whenever a Forest you control enters, Battlewand Oak gets +2/+2 until end of turn.
Whenever you cast a Treefolk spell, Battlewand Oak gets +2/+2 until end of turn.

Kurbis, Harvest Celebrant

Kurbis, Harvest Celebrant enters with a number of +1/+1 counters on it equal to the amount of mana spent to cast it.
Remove a +1/+1 counter from Kurbis: Prevent all damage that would be dealt this turn to another target creature with a +1/+1 counter on it.

Generous Ent

Reach
When Generous Ent enters, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: 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.)

Great Oak Guardian

Flash (You may cast this spell any time you could cast an instant.)
Reach
When Great Oak Guardian enters, creatures target player controls get +2/+2 until end of turn. Untap them.

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.
Dauntless Dourbark has trample as long as you control another Treefolk.

Heartwood Storyteller

Whenever a player casts a noncreature spell, each of that player's opponents may draw a card.

Shriekwood Devourer

Trample
Whenever you attack with one or more creatures, untap up to X lands, where X is the greatest power among those creatures.

Deadwood Treefolk

Vanishing 3 (This creature enters with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
When Deadwood Treefolk enters or leaves the battlefield, return another target creature card from your graveyard to your hand.

Treefolk Harbinger

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

Orchard Strider

When Orchard Strider enters, create two Food tokens. (They're artifacts with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")
Basic landcycling {1}{G} ({1}{G}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Ulvenwald Observer

Whenever a creature you control with toughness 4 or greater dies, draw a card.

Timber Protector

Other Treefolk creatures you control get +1/+1.
Other Treefolk and Forests you control have indestructible.

Leaf-Crowned Elder

Kinship — At the beginning of your upkeep, you may look at the top card of your library. If it shares a creature type with Leaf-Crowned Elder, you may reveal it. If you do, you may play that card without paying its mana cost.

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.

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.

Ghastbark Twins

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Ghastbark Twins can block an additional creature each combat.