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.

Rootgrapple

Destroy target noncreature permanent. If you control a Treefolk, draw a card.

Murmuring Bosk

({T}: Add {G}.)
As Murmuring Bosk enters, you may reveal a Treefolk card from your hand. If you don't, Murmuring Bosk enters tapped.
{T}: Add {W} or {B}. Murmuring Bosk deals 1 damage to you.

Sapling of Colfenor

Indestructible
Whenever Sapling of Colfenor attacks, reveal the top card of your library. If it's a creature card, you gain life equal to that card's toughness, lose life equal to its power, then put it into your hand.

Vivid Grove

Vivid Grove enters tapped with two charge counters on it.
{T}: Add {G}.
{T}, Remove a charge counter from Vivid Grove: Add one mana of any color.

Timber Protector

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

Lignify

Enchant creature
Enchanted creature is a Treefolk with base power and toughness 0/4 and loses all abilities.

Doran, the Siege Tower

Each creature assigns combat damage equal to its toughness rather than its power.

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.

Everbark Shaman

{T}, Exile a Treefolk card from your graveyard: Search your library for up to two Forest cards, put them onto the battlefield tapped, then shuffle.

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.

Forest

Safewright Quest

Search your library for a Forest or Plains card, reveal it, put it into your hand, then shuffle.

Recross the Paths

Reveal cards from the top of your library until you reveal a land card. Put that card onto the battlefield and the rest on the bottom of your library in any order. Clash with an opponent. If you win, return Recross the Paths to its owner's hand. (Each clashing player reveals the top card of their library, then puts that card on the top or bottom. A player wins if their card had a higher mana value.)

Indomitable Ancients

Orchard Warden

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

Swamp

Plains

Bosk Banneret

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

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.