A grass sacred to Ganesha, used for ritual purposes, also called Kusha grass.
Durva grass is responsible that snakes have forked tongues.
Read about Durva Grass
https://storibuzz.in/why-durva-grass-or-arugampul-is-dear-to-lord-ganesha/
http://utkarshspeak.blogspot.com/2013/12/do-you-know-why-snakes-have-forked.html