For the vanilla item, see Seeds
Winter Wheat is a variant of wheat which grows in cold temperatures and has a slightly bluer texture than vanilla (durum) wheat. The first growth stage (14% grown) won't occur unless the current biome temperature drops below 50°F (10°C, 0.5°MC). After that, it will grow normally (following temperature and rainfall influences, as listed).
Winter wheat seeds will drop when breaking Tall Grass blocks in a biome that is natively cold (any biome with an average temperature of 0.3°MC or lower: taiga, cold taiga, ice plains, etc).
Winter wheat works exactly like vanilla wheat except that it will drop winter wheat seeds instead of regular seeds when harvested.