sycamore) Platycarya Platycerium (staghorn fern) Platycladus (Chinese arborvitae) Platycodon (balloon flower) Platystemon (creamcups) Plectranthus an orchid genus Pleioblastus Pleione (an orchid genus) Pleiospilos (living granite) Pleurothallis (an orchid genus) Plumeria (frangipani) Poa Podalyria Podocarpus Podophyllum (mayapple) Podranea Polemonium (jacob's ladder, abscess root) Polianthes Poliothyrsis Polygala (milkwort, seneca, snakeroot) Polygonatum Polygonum (knotweed, knotgrass) Polypodium Polyscias Polystichum Poncirus Pongamia Pontederia (pickerel weed) Populus (aspen, poplar, cottonwood) Porana Portea Portulaca (purslane, moss rose) Portulacaria Posoqueria Potamogeton Potentilla (cinquefoil) Pothos × Potinara (hybrid orchid genus) Pratia Primula (primrose) Prinsepia Pritchardia Proboscidea (unicorn plant) Promenaea an orchid genus Prosopis (mesquite) Prostanthera (mint bush) Protea Prumnopitys Prunella (self-heal) Prunus (almond, apricot, cherry, peach, plum) Pseuderanthemum Pseudocydonia Pseudolarix (golden-larch) Pseudopanax Pseudosasa Pseudotsuga (douglas-fir) Pseudowintera Psilotum Psychopsis (butterfly orchid) Psylliostachys (statice) Ptelea Pteris (brake, table fern) Pterocactus Pterocarya (wingnut) Pteroceltis Pterocephalus Pterodiscus Pterostyrax Ptilotus Ptychosperma Pueraria Pulmonaria (lungwort) Pulsatilla Pultenaea Punica (pomegranate) Purshia Puschkinia Putoria Puya Pycnanthemum Pycnostachys Pyracantha (firethorn) Pyrola (wintergreen) Pyrostegia Pyrrosia Pyrus (pear) Q Quamoclit Quaqua Quercus (oak) Quesnelia Quisqualis Quince R Ramonda Ranunculus (buttercup, crowfoot) Ranzania Raoulia Raphia (raffia) Ratibida Ravenala (traveler's tree) Rebutia Rehderodendron Rehmannia Reineckea Reinwardtia Reseda (Mignonette) Retama Rhamnus Rhaphidophora Rhaphiolepis Rhapidophyllum (needle palm) Rhapis (lady palm) Rheum (rhubarb) Rhexia Rhipsalis Rhodanthe (strawflower) Rhodanthemum Rhodiola Rhodochiton Rhododendron Rhodohypoxis Rhodophiala Rhodothamnus Rhodotypos Rhoeo Rhoicissus Rhombophyllum Rhus (sumac) Rhynchelytrum Rhynchostylis (an orchid genus) Ribes (currant) Richea Ricinus (castor-oil plant) Rigidella Robinia Rodgersia Rodriguezia an orchid genus Rohdea Romanzoffia Romneya (Matilija poppy, tree poppy) Romulea Rondeletia Rosa (rose) Roscoea Rosmarinus (rosemary) Rossioglossum an orchid genus Rothmannia Roystonea (royal palm) Rubus (raspberry) Rudbeckia (coneflower) Ruellia Rumex (dock) Rumohra Rupicapnos Ruschia Ruscus Russelia Ruta (rue) S Sabal (palmetto) Saccharum (plume grass, sugar cane) Sadleria Sagina (pearlwort) Sagittaria (arrowhead) Salix (willow) Salpiglossis Salvia (sage) Salvinia Sambucus (elder) Sanchezia Sandersonia Sanguinaria (bloodroot) Sanguisorba (burnet) Sanicula Sansevieria Santolina Sanvitalia (creeping zinnia) Sapindus Sapium (tallow tree) Saponaria (soapwort) Sarcocapnos Sarcocaulon Sarcococca Saritaea, see Bignonia magnifica Sarmienta Sarracenia (pitcher plant) Sasa Sassafras Satureja (savory) Sauromatum Saxegothaea Saxifraga (saxifrage) Scabiosa (scabious plant) Scadoxus (blood lily) Scaevola Schefflera Schima Schinus Schisandra Schizachyrium Schizanthus Schizopetalon Schizophragma Schizostylis Schlumbergera Schoenoplectus Schomburgkia an orchid genus Schotia Schwantesia Sciadopitys Scilla (including the former genus Chionodoxa) Scindapsus Scirpoides Sclerocactus Scoliopus Scopolia Scrophularia (figwort) Scutellaria Securinega Sedum (stonecrop) Selaginella Selago Selenicereus Selinum Semele Semiaquilegia Semiarundinaria Sempervivum (hens and chicks) Senecio (ragwort) Senna Sequoia (coast redwood) Sequoiadendron (giant sequoia) Seriphidium Serissa Serruria Sesbania Sesleria Setaria Shepherdia Shibataea Shortia Sibiraea Sidalcea