Savannah Grass is a naturally occurring cubic block that covers the topmost layer of the ground of Savannah biomes on top of several blocks of Rocky Dirt, until the Fossil layer begins underneath; similar to green Grass in other biomes that usually covers blocks of Dirt.
The top face of the Savannah Grass block resembles yellow ochre short grass arranged criss-cross, while the underside resembles Rocky Dirt and the four sides feature both textures with nearly egg yolk yellow thin and long grass stalks forming a row at the top with dark brown joints as well as a dark brown transition zone between the grass stalks and the predominantly Rocky Dirt texture below.
While Savannah Tallgrass, Wildflowers and Shrubs can often be found on Savannah Grass right after world generation, these plants do not grow on blocks of Savannah Grass by themselves and so cannot be "cultivated".
How to obtain
Naturally, Savannah Grass can only be found in Savannah biomes on all game worlds created after the Early Access update R14.
You won't need to equip any Power Cells to pick up Savannah Grass blocks. Of course you won't be able to pick up such half-sized blocks on game worlds, on player claims or in Adventures where your Permission rank is not sufficient (mainly when you are merely a visitor), which can only be changed by the owner of the game world, the respective claim owner or Adventure creator.
Just like Grass, the yellow-y Savannah Grass can "spread" on Rocky Dirt since update R56 on September 27th 2018, which means that Rocky Dirt blocks will transform into Savannah Grass when "under the sun" on the surface as long as at least one block of Savannah Grass is adjacent to the Rocky Dirt block/s (for this purpose, Savannah Grass can also be placed underneath blocks of Rocky Dirt).
On the other hand, Savannah Grass can also be transformed into Rocky Dirt - by using an AOE Gauntlet Smash on it. No Power Cell is necessary for this. This ground smash can only performed with 75% Stamina or more of the possible maximum and if a melee Weapon has been drawn (including the default Twig).
The Gauntlet Smash will be performed on the block directly in front of your player character even if you point your cursor at any spot farther away. This point of impact will then be the center of a star-shaped area of transformation of 3 blocks to all 4 sides on the ground, 2 blocks diagonally to all 4 sides, 3 blocks downwards at maximum and 1 block upwards.
The tips of the "star" (the third block to all 4 sides) outside the central 3x3 area of effect will be affected a little less by the Gauntlet Smash. On these "tips", plants like Savannah Tallgrass, Shrubs and Wildflowers will prevail. However, these three listed plants will only be destroyed if at least a Stone Mining Cell or better is equipped.
Neither the melee Weapon nor the Mining Cell will lose any durability when the Gauntlet Smash is used.
The biome-specific Savannah Grass (also Dead Grass, Detritus, Matted Needles, Savannah Tallgrass and Rocky Dirt) cannot be corrupted by throwing Corrupt Bombs at it - unlike ordinary green Grass blocks and ordinary Dirt that can be corrupted to then become Corrupted Grass and Corrupted Dirt.
How to use
Savannah Grass can be used for building purposes and decoration.
You can place Savannah Grass blocks anywhere into the game world just like they are, like any other type of placeable block, by putting (a stack of) them into a slot of your quickbar, selecting this quickslot by number or scrolling and by then clicking your right mouse button while pointing at the spot where you want to place them.
Savannah Grass blocks can be rotated in all directions by holding "R" (as the default key) and moving the left mouse button. The chosen rotation angle can then be "locked" too by simply typing "r", so that all items of the same stack will be placed facing the same direction.
Blocks of Savannah Grass, like all placeable objects and blocks, can also be put on display by placing them into the slots of display containers like Placemats, Stone Wall Shelves, Hidden Temple Altars, Galactic Grav-Chambers, Frozen Containers, Holiday Decorative Trees, Snow Buried Containers, Wood Planters, Flower Pots or the like, where they will usually be reduced in size while on display and cannot be transformed.