Pappusgrass _Pappophorum_ 24 Paragrass _Panicum purpurascens_ 23 Parrotfeather _Myriophyllum_ 48 Parsnip _Pastinaca_ 49 Parthenium _Parthenium_ 49 Partridgepea _Cassia_ 31 Paspalum _Paspalum_ 24 Pawpaw _Asimina_ 55 Pea _Pisum_ 33 Peanut _Arachis_ 30 Pear _Pyrus communis_ 57 Pearlmillet _Pennisetum glaucum_ 24 Pearlwort _Sagina_ 52 Peashrub _Caragana_ 31, 56 Peavine _Lathyrus_ 32 Pecan _Carya illinoensis_ 56 Pectis _Pectis_ 49 Pedicularis _Pedicularis_ 49 Pellitory _Parietaria_ 49 Pencilflower _Stylosanthes_ 34 Pennisetum _Pennisetum_ 24 Pennycress _Thlaspi_ 54 Penstemon _Penstemon_ 49 Penthorum _Penthorum_ 49 Peppergrass _Lenidium densiflorum_ 46 Pepperweed _Lepidium_ 46 Pepperwort _Marsilea_ 28 Perilla _Perilla_ 49 Persimmon _Diospyros_ 56 Phacelia _Phacelia_ 49 Phlox _Phlox_ 49 Pigeonpea _Cajanus_ 31 Pigweed _Amaranthus_ 35 Pimpernel _Anagallis_ 35 Pinedropseed _Blepharoneuron_ 19 Pinegrass _Calamagrostis rubescens_ 20 Pinweed _Lechea_ 46 Plantain _Plantago_ 50 Plum _Prunus_ 57 Plumegrass _Erianthus_ 21 Poisonhemlock _Conium maculatum_ 40 Poisonivy _Rhus radicans_ 58