Created by Gorbert Vanhousserhoffen in the first season, Symbiotic Grass looks exactly like regular grass, except that it has the tendency to wriggle and squirm when people are near it.
When a person lies in the grass, it rubs gently against them and produces the most soothing feeling of peace and tranquility. A person lying in the grass feels well rested, carefree and happy. In return, the grass feeds on the contentment in creates in its host, thus forming a symbiotic cycle.
There are no adverse effects to lying in the grass, but be warned: pulling yourself away from such contentment is very difficult. If you can't summon up the willpower to roll off of the grass, you may find yourself spending quite a bit of time there. Not that you'll mind too much.