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
Daenerys Targaryen hears of the ghost grass in the Shadow Lands beyond Asshai from Ser Jorah Mormont.
A Clash of Kings
In Qarth, following the destruction of the House of the Undying, Xaro Xhoan Daxos tells Daenerys that ghost grass is growing in the Garden of Gehane.