Jungle Grass Seeds

Jungle Grass Seeds are a kind of Seeds that can be placed on Mud Blocks to grow jungle grass and make an artificial Underground Jungle or Jungle, depending on the depth. Seeds can be found by mowing grass in jungle environments.

Like a natural one, an artificial jungle will become inhabited with the respective mobs, i.e. Hornets and Man Eaters underground and Snatchers, Piranhas, Jungle Bats and Jungle Slimes above ground.

Farming Underground Jungles
It is possible to find rare items such as Nature's Gift and Jungle Armor in a player-made underground jungle. The seeds can be obtained by destroying jungle grass (the small pieces sticking out of the ground, not the mud block that has grass growing on it) which is found in the Underground Jungle.

The most efficient setup for creating an Underground Jungle "farm" for harvesting Jungle Roses, Jungle Seeds and Natures' Gifts is by creating a floor of jungle grass, and a ceiling 3 blocks in height, then on the next layer up, do the same, but this time also add a middle layer so you have 3 lines with 1 space between each and repeat. You can then harvest it easily by using a Muramasa, Blade of Grass, Hammer or similar long reaching weapon or tool to harvest all 3 layers (The one you stand on and the two above it). Note that some items will get stuck above, but will be collected as you rise up the farm layers. An additional row of platforms right under the ceiling will prevent vines from growing and taking up space for the grass, while also letting the players enter without rising the height of the farm.

This method is sometimes questioned due to the vines that can hang down and prevent some items spawning (which can be avoided if there is a layer of any material other than mud right under the ceiling), however in Underground Jungle biomes, grass and roses seem to grow faster than vines so this should result in better yields in a smaller space than a simple 3 block high tunnel farm.