Polypogon viridis
Polypogon viridis, the beardless rabbitsfoot grass, water bent, is a species of perennial grass in the family Poaceae. They have a self-supporting growth form and simple, broad leaves. Individuals can grow to 0.43 m. They are native to southern Europe, Macaronesia, North and East Africa, western and central Asia, India, Yunnan, and Vietnam.
It is a common established neophyte in the UK.