Redcedar _Juniperus virginiana_ 57 Redtop _Agrostis alba_ 18 Reed _Phragmites_ 24 Reedgrass _Calamagrostis_ 20 Rhodesgrass _Chloris gayana_ 20 Rhubarb _Rheum_ 51 Rice _Oryza_ 23 Ricegrass _Oryzopsis_ 23 Ricegrass, Mandan X _Striporyzopsis caduca_ 26 Ringwing _Cycloloma_ 40 Rockcress _Arabis_ 36 Rocket _Hesperis_ 44 Rocketsalad _Eruca_ 42 Rockjasmine _Androsace_ 35 Rose _Rosa_ 58 Rosegentian _Sabatia_ 52 Rosemallow _Hibiscus_ 44 Rosinweed _Silphium_ 53 Rotala _Rotala_ 51 Ruellia _Ruellia_ 51 Rush _Juncus_ 28 Rushpea _Hoffmanseggia_ 32 Russianolive _Elaeagnus_ 56 Russianthistle _Salsola_ 52 Rutabaga _Brassica rapa_ 38 Rye _Secale_ 25 Ryegrass _Lolium_ 22 Sacaton _Sporobolus_ 25, 26 Safflower _Carthamus_ 38 Sage _Salvia_ 52 Sagebrush _Artemisia_ 36, 55 Sagewort _Artemisia_ 36 Sainfoin _Onobrychis_ 33 Salsify _Tragopogon_ 54 Saltbush _Atriplex_ 37, 55 Saltgrass _Distichlis_ 21 Samolus _Samolus_ 52 Sandbur _Cenchrus_ 20 Sandgrass _Triplasis_ 26 Sandreed _Calamovilfa_ 20 Sandverbena _Abronia_ 35 Sandwort _Arenaria_ 36