Dark Wheat is the Nether equivalent of Wheat on the surface. Like wheat, dark wheat is grown by planting Seeds on farmland
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Dark Wheat as it is first planted (left), and ready to harvest (right).

(in this case, tilled Netherdirt.) Seeds of Dark Wheat are obtained by using a hoe on Nether Dirt. Dark Wheat, as the name implies, can ONLY be grown in total darkness, making it very apropriate for the Nether. It grows over time or if you use Ghast Bonemeal on Dark Wheat, it will instantly grow and can be harvested to aquire the item: Dark Wheat, which is used in the crafting of Devil's Bread. Devil's Bread heals 5 hunger points.