Key for identifying common grassy weed seedlings in PA
Grass Leaves

A = annual, P = perennial, WA = winter annual

1. Stem triangular, solid, three ranked leaves Yellow Nutsedge, Cyperus esculentus, P
1. Stem flat to round, hollow, two ranked leaves Grasses, Gramineae spp.
    A. Auricles present Quackgrass, Agropyron repens, P
    A. Auricles absent  
         1. Ligule absent Barnyardgrass, Echinochloa crusgalli, A
         1. Ligule present  
             2. Ligule a fringe of hairs  
                 3. Sheath round with overlapping margins  
                     4. Sheath covered with long hairs Witchgrass, Panicum capillare, A
                     4. Sheath smooth  
                         5. Margins of the sheath hairy  
                             6. Leaf blade rough above, smooth to
                                 somewhat rough below 		Green Foxtail, Setara viridis, A
                             6. Leaf blade covered with short hairs
                                 above, smooth and keeled below 		Giant Foxtail, Setaria faberii, A
                         5. Margins of the sheath not hairy  
                             6. Collar hairy on the margins Stinkgrass, Erogrostis cilianensis, A
                             6. Collar not hairy on the margins Fall Panicum, Panicum dichotomiflorum, A
                 3. Sheath distinctly flattened, smooth, with overlapping
                     margins		  
                     4. Collar divided, not hairy on the margins Bristly Foxtail, Setaria verticillata, A
                     4. Collar not divided, hairy on the margins  
                         5. Leaf blade has a few long hairs near the base Yellow Foxtail, Setaria glauca, A
                         5. Leaf blade smooth Sandbur, Cenchus pauciflorus, A
             2. Ligule membranous  
                 3. Sheath round to oval  
                     4. Sheath smooth, split with overlapping margins  
                         5. Leaf blade smooth above and below, midrib white
                             above, prominent below		  
                             6. Thick, white rhizomes just below soil surface Johnsongrass, Sorghum halepenese, P
                             6. No rhizomes, fibrous root system like corn Shattercane, Sorghum bicolor, A
                         5. Leaf blade rough above and below, midrib not
                             white or prominent below		  
                             6. Short, scaly rhizomes at or below soil surface Wirestem Muhly, Muhlenbergia frondosa, P
                             6. No short, scaly rhizomes at or below soil
                                 surface		 Nimblewill, Muhlenbergia schreberi, P
                     4. Sheath hairy, closed to near the top       
                         5.   Sheath short, hairy Cheat, Bromus secalinus, A or WA
                         5.   Sheath densely soft, white, hairy, frequently
                                purplish		 Downy Bromegrass, Bromus tectorum, A or WA
                 3. Sheath distinctly flattened, split with
                     overlapping margins		  
                     4. Sheath smooth or sparsely hairy  
                         5. Leaf blade smooth above, smooth and keeled
                             below, tip boat-shaped		 Annual Bluegreass, Poa annua, A or WA
                         5. Leaf blade smooth above, a few hairs near base;
                             smooth, keeled below		 Small Crabgrass, Digitaria ischaemum, A
                     4. Sheath hairy  
                         5.   Leaf blade long, hairy near the base above,
                              smooth below		 Goosegrass, Eleusine indica, A
                         5. Leaf blade hairy above and below, ligule
                             often reddish or purplish		 Large Crabgrass, Digitaria sanguinalis, A