Patron of the Orochi

Snake offering (You may cast this spell any time you could cast an instant by sacrificing a Snake and paying the difference in mana costs between this and the sacrificed Snake. Mana cost includes color.)
{T}: Untap all Forests and all green creatures. Activate only once each turn.

Dryad Arbor

(Dryad Arbor isn't a spell, it's affected by summoning sickness, and it has "{T}: Add {G}.")

Sylvan Anthem

Green creatures you control get +1/+1.
Whenever a green creature you control enters, scry 1.

Beacon of Creation

Create a 1/1 green Insect creature token for each Forest you control. Shuffle Beacon of Creation into its owner's library.

Tangle Golem

Affinity for Forests (This spell costs {1} less to cast for each Forest you control.)

Llanowar Druid

{T}, Sacrifice Llanowar Druid: Untap all Forests.

Waiting in the Weeds

Each player creates a 1/1 green Cat creature token for each untapped Forest they control.

Primal Bellow

Target creature gets +1/+1 until end of turn for each Forest you control.

Skyshroud Claim

Search your library for up to two Forest cards, put them onto the battlefield, then shuffle.

Coiling Woodworm

Coiling Woodworm's power is equal to the number of Forests on the battlefield.

Woodland Guidance

Return target card from your graveyard to your hand. Clash with an opponent. If you win, untap all Forests you control. (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.)
Exile Woodland Guidance.

Treefolk Seedlings

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

Tel-Jilad Lifebreather

{G}, {T}, Sacrifice a Forest: Regenerate target creature.

People of the Woods

People of the Woods's toughness is equal to the number of Forests you control.

Nessian Game Warden

When Nessian Game Warden enters, look at the top X cards of your library, where X is the number of Forests you control. You may reveal a creature card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Nature's Lore

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Aspect of Wolf

Enchant creature
Enchanted creature gets +X/+Y, where X is half the number of Forests you control, rounded down, and Y is half the number of Forests you control, rounded up.

Hunting Wilds

Kicker {3}{G} (You may pay an additional {3}{G} as you cast this spell.)
Search your library for up to two Forest cards, put them onto the battlefield tapped, then shuffle.
If this spell was kicked, untap all Forests put onto the battlefield this way. They become 3/3 green creatures with haste that are still lands.

Village Elder

Gaea's Touch

{0}: You may put a basic Forest card from your hand onto the battlefield. Activate only as a sorcery and only once each turn.
Sacrifice Gaea's Touch: Add {G}{G}.

Uktabi Wildcats

Uktabi Wildcats's power and toughness are each equal to the number of Forests you control.
{G}, Sacrifice a Forest: Regenerate Uktabi Wildcats.

Three Visits

Search your library for a Forest card, put it onto the battlefield, then shuffle.

Ashaya, Soul of the Wild

Ashaya, Soul of the Wild'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.)

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.

Silverglade Elemental

When Silverglade Elemental enters, you may search your library for a Forest card, put that card onto the battlefield, then shuffle.