Thaghaam Stipagrostis hirtigluma
It is a grass that grows on mountains. It starts green and then turns white as it dries up. It has rough panicles, wher inflorescence of the plant takes place. It belongs to the Gramineae family which is known for being aromatic and white for adult plants. Stipagrostis hirtigluma can be found in stone valleys, and the Arabic word was mentioned by Prophet Muhammad (PBUH).
Jabir reported that Abu-Quhafah was brought (or came) the year (or the day) of Fath (the Conquest of Makkah) and his head and beard were like white grass. So, he (or someone) asked his wives to help him change this. [Saheeh Muslim, Book of Clothing and Adornment]