A moratorium is in effect on adding information from Fire and Blood until December 20th.
Ghost grass is a type of grass that grows throughout the Shadow Lands in eastern Essos, both on its shores and in the valleys between its mountains. Ghost grass is taller than a human on horseback and has stalks as pale as milkglass. It is an invasive plant that overwhelms other grass. The Dothraki believe that ghost grass glows with the spirits of the damned and will one day cover the entire world.
A Game of Thrones
A Clash of Kings