1) Old witch grass 2) Old witchgrass 3) Panic grass 4) Panicum capillare 5) Tumble grass 6) Witch grass 1) Quack grass 
(from the article `panicum`) Witchgrass (P. capillare), a tufted annual, is a common weed in fields and disturbed areas. Its large, purplish flower clusters break off and are ...
[n] - North American grass with slender brushy panicles
old witch grass noun North American grass with slender brushy panicles; often a weed on cultivated land