Solidarity

Creatures you control get +0/+5 until end of turn.

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."

Stoneskin

Flash
Enchant creature
Enchanted creature gets +0/+10.

Plains

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.

Treefolk Seedlings

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

Sol Ring

Black Poplar Shaman

Forest

Old Man Willow

Old Man Willow's power and toughness are each equal to the number of lands you control.
Whenever Old Man Willow attacks, you may sacrifice another creature or a token. When you do, target creature an opponent controls gets -2/-2 until end of turn.

Doran, the Siege Tower

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

Colfenor, the Last Yew

Vigilance, reach
Whenever Colfenor, the Last Yew or another creature you control dies, return up to one other target creature card with lesser toughness from your graveyard to your hand.

Swamp

Bosk Banneret

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

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.

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.

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.

Ancient Lumberknot

Each creature you control with toughness greater than its power assigns combat damage equal to its toughness rather than its power.