Grasses

Grass enables many plants plants to grow on it. Grass covers most of the above ground landscape. There are five types of grass: Normal, Corrupt, Mushroom, Jungle and Hallow.

Grass types
Normal grass spreads over Dirt Blocks. Above ground grass blocks will grow Mushroom, Daybloom, flowers, and weeds, all of which can be cut with any tool or weapon. If a grass block has room below it, vines will grow downward from it. Grass is necessary in order to plant trees. Grass does not spread below level elevations, but can be placed in lower layers block by block using the Staff of Regrowth or Grass Seeds. This grass will not grow flowers and tall grass, and trees planted on it will never mature. Grass occurs naturally above ground, but it may also be planted by using grass seeds bought from the Dryad.

Corrupted grass spreads over Dirt Blocks and normal grass. Above ground corrupt grass blocks will grow Vile Mushrooms, Deathweed, corrupted flowers, and weeds, all of which can be cut with any tool or weapon. In addition, corrupted thorns will grow from corrupted grass in any condition. Vines do not grow from corrupted grass. Like normal grass, it does not spread below level elevations. This type of grass occurs naturally in corrupted areas and may also be planted with Corrupt Seeds dropped by the Eye of Cthulhu. A large enough amount of corrupted grass will turn the area into a Corruption biome. In hardmode, corrupted grass will convert blocks that are up to three squares away into their corrupted variants. This includes turning jungle grass and normal grass below level elevations into corrupted grass. It also gives off particles.

Mushroom grass spreads over Mud Blocks and will grow Glowing Mushrooms and giant glowing mushrooms if underground at a depth of 0 feet or below. Patches of mud seeded with mushroom grass can be found in some caverns underground, generally with several tall giant glowing mushrooms. Mushroom Grass Seeds are an uncommon drop from glowing mushrooms and giant glowing mushrooms. Mushroom grass glows faintly and can be used as a natural light source. Mushroom grass blocks are unaffected by corruption. When aboveground, Mushroom Grass appears to actually grow faster. (More testing needed.)

Jungle grass spreads over Mud Blocks at any depth, and will grow vines, jungle thorns, Moonglow, Jungle Spores, Jungle Roses, and Nature's Gift. Jungle grass occurs naturally in the Jungle and Underground Jungle area but can also be planted from Jungle Grass Seeds which are a rare drop from jungle grass weeds and glowing flowers. From version 1.0.4 jungle plants grow underwater in contrast to other plants.

Hallowed grass spreads over Dirt Blocks and normal grass. Above ground hallowed grass blocks will grow Mushroom, Daybloom, and flowers, similar to normal grass. Like corrupt grass, hallowed grass does not spread below 0 feet elevation. Hallowed grass does not occur naturally until a world enters hardmode, and may be created with Hallowed Seeds sold by the Dryad in hardmode or with Holy Water. A large enough amount of hallowed grass will turn the area into a Hallow biome. At hardmode hallowed grass will convert blocks that are up to three squares away into their hallowed variants, although it does not turn jungle grass into hallowed grass. It gives off a sparkle particle effect.

Grass growth
Grass of any type spreads from existing blocks to other blocks of the correct soil type. The block to receive grass must be within 2 blocks of another grass block, and exposed on at least one side or corner. If it is surrounded by solid blocks, grass cannot spread there, although normal grass can be placed on unexposed blocks on world creation. The Corruption's thorny bushes count as grass for purposes of spreading. The bushes can grow up to 4 blocks in height and width, as long as there is open space.