Oemleria cerasiformis (Oso berry)
Oenanthe sarmentosa (Water-parsley)
Oenothera
    caespitosa ssp. marginata (Tufted evening primrose)
    californica ssp. avita (Desert evening primrose)
    californica ssp. californica (California evening primrose)
    californica ssp. eurekensis (Eureka Dunes evening primrose)
    cavernae (Cave-dwelling evening primrose)
    deltoides ssp. deltoides (Dune primrose)
    elata ssp. hirsutissima (Hairy evening primrose)
    elata ssp. hookeri (Hooker's evening primrose)
    primiveris ssp. bufonis (Large yellow primrose)
    rosea (Rose evening primrose)*
    sinuosa (Wavyleaf bee blossom)*
    suffrutescens (Scarlet gaura)
Oligomeris linifolia (Oligomeris)
Olneya tesota (Desert ironwood)
Oncosiphon piluliferum (Globe chamomile)*
Ophioglossum californicum (California adder's-tongue)
Opuntia
    acanthocarpa var. coloradensis, see Cylindropuntia acanthocarpa var. coloradensis
    basilaris var. basilaris (Beavertail cactus)
    basilaris var. brachyclada (Short-joint beavertail cactus)
    bigelovii, see Cylindropuntia bigelovii
    chlorotica (Pancake prickly-pear)
    echinocarpa, see Cylindropuntia echinocarpa
    erinacea var. erinacea, see Opuntia polyacantha var. erinacea
    ficus-indica (Mission cactus)*
    fosbergii (Fosberg's cholla)
    littoralis (Coast prickly-pear)
    occidentalis (Western prickly-pear)
    oricola (Chaparral prickly-pear)
    parishii (Mat cholla)
    parryi var. parryi, see Cylindropuntia californica var. parkeri
    phaeacantha (Desert prickly-pear)
    polyacantha var. erinacea (Mojave prickly-pear)
    prolifera, see Cylindropuntia prolifera
    ramosissima, see Cylindropuntia ramosissima
    vaseyi (Vasey's prickly-pear)
    wolfii, see Cylindropuntia wolfii
Oreonana vestita (Woolly mountain parsley)
Oreostemma alpigenum var. andersonii (Alpine aster)
Ornithostaphylos oppositifolia (Baja birdbush)
Orobanche
    bulbosa (Chaparral broom-rape)
    californica ssp. feudgei (California broom-rape)
    cooperi (Cooper's broom-rape)
    fasciculata (Clustered broom-rape)
    parishii ssp. brachyloba (Short-lobed broom-rape)
    parishii ssp. parishii (Parish's broom-rape)
    uniflora (Naked broom-rape)
    valida ssp. valida (Rock Creek broom-rape)
    vallicola (Valley broom-rape)
Orthilia secunda (One-sided wintergreen)
Osmadenia tenella (Three-spot)
Osmorhiza
    berteroi (Mountain sweet-cicely)
    brachypoda (Sweet-cicely)
    chilensis, see Osmorhiza berteroi
Osteospermum ecklonis (African daisy)*
Oxalis
    albicans ssp. californica, see Oxalis californica
    californica (Wild oxalis)
    corniculata (Creeping wood-sorrel)*
    pes-caprae (Bermuda buttercup)*
    pilosa (Hairy wood sorrel)
Oxypolis occidentalis (Western cowbane)
Oxystylis lutea (False-clover)
Oxytheca
    caryophylloides, see Sidotheca caryophylloides
    emarginata, see Sidotheca emarginata
    parishii var. cienegensis, see Acanthoscyphus parishii var. cienegensis
    parishii var. goodmaniana, see Acanthoscyphus parishii var. goodmaniana
    parishii var. parishii, see Acanthoscyphus parishii var. parishii
    perfoliata (Roundleaf oxytheca)
    trilobata, see Sidotheca trilobata
Oxytropis oreophila var. oreophila (Mountain oxytrope)
Packera
    bernardina (San Bernardino ragwort)
    ionophylla (Tehachapi ragwort)
    multilobata (Basin butterweed)
Paeonia californica (Wild peony)
Palafoxia
    arida var. arida (Spanish needles)
    arida var. gigantea (Giant Spanish needles)
Panicum urvilleanum (Desert panic grass)
Papaver californicum (Fire poppy)
Parapholis incurva (Curved sicklegrass)*
Parietaria
    hespera var. hespera (Pellitory)
    pensylvanica (Pennsylvania pellitory)
Parkinsonia
    florida (Palo verde)
    florida fruit (Palo verde)
    microphylla (Littleleaf palo verde)
Parnassia
    californica, see Parnassia palustris
    palustris (Grass-of-parnassus)
Paspalum
    dilatatum (Dallis grass)*
    distichum (Knot grass)
Pectis papposa var. papposa (Chinchweed)
Pectocarya
    heterocarpa (Hairy-leaved pectocarya)
    linearis ssp. ferocula (Slender pectocarya)
    penicillata (Winged pectocarya)
    platycarpa (Broad-fruited pectocarya)
    recurvata (Curvenut pectocarya)
    setosa (Bristly pectocarya)
Pedicularis
    densiflora (Indian warrior)
    semibarbata (Pine lousewort)
Pellaea
    andromedifolia (Coffee fern)
    mucronata var. californica (California cliff brake)
    mucronata var. mucronata (Bird's-foot fern)
    truncata (Cliff brake)
Pennisetum
    clandestinum (Kikuyu grass)*
    setaceum (Fountaingrass)*
Penstemon
    caesius (San Bernardino beardtongue)
    calcareus (Limestone beardtongue)
    californicus (California beardtongue)
    centranthifolius (Scarlet bugler)
    clevelandii var. clevelandii (Cleveland's beardtongue)
    clevelandii var. connatus (San Jacinto beardtongue)
    eatonii var. undosus (Firecracker penstemon)
    floridus var. austinii (Austin's beardtongue)
    fruticiformis var. fruticiformis (Desert beardtongue)
    grinnellii var. grinnellii (Grinnell's penstemon)
    grinnellii var. scrophularioides (Grinnell's penstemon)
    heterophyllus var. australis (Foothill penstemon)
    heterophyllus var. heterophyllus (Foothill penstemon)
    labrosus (San Gabriel beardtongue)
    labrosus (yellow form) (San Gabriel beardtongue)
    laetus var. laetus (Mountain blue penstemon)
    newberryi var. newberryi (Pride of the mountains)
    palmeri var. palmeri (Palmer's penstemon)
    pseudospectabilis (Desert penstemon)
    rostriflorus (Beaked penstemon)
    speciosus (Royal penstemon)
    spectabilis var. spectabilis (Showy penstemon)
    spectabilis var. subviscosus (Showy penstemon)
    stephensii (Stephens' beardtongue)
    thurberi (Thurber penstemon)
    utahensis (Utah penstemon)
Pentachaeta
    aurea ssp. allenii (Allen's daisy)
    aurea ssp. aurea (Golden-rayed pentachaeta)
    lyonii (Lyon's pentachaeta)
Pentagramma
    triangularis ssp. triangularis (Goldback fern)
    triangularis ssp. viscosa (Silverback fern)
Perideridia
    parishii ssp. latifolia (Wide-leaved Parish's yampah)
    parishii ssp. parishii (Parish's yampah)
Peritoma arborea (Bladderpod)
Perityle emoryi (Rock daisy)
Petalonyx
    nitidus (Shinyleaf sandpaper plant)
    thurberi (Sandpaper plant)
Petrophyton caespitosum (Rock spiraea)
Petrorhagia dubia (Hairypink)*
Petunia parviflora (Seaside petunia)
Peucephyllum schottii (Desert-fir)
Phacelia
    affinis (Limestone phacelia)
    anelsonii (Aven Nelson's phacelia)
    austromontana (Southern mountain phacelia)
    brachyloba (Yellow-throated phacelia)
    calthifolia (Caltha-leaved phacelia)
    campanularia ssp. campanularia (Desert bluebells)
    campanularia ssp. vasiformis (Desert bluebells)
    cicutaria var. cicutaria (Caterpillar phacelia)
    cicutaria var. hispida (Caterpillar phacelia)
    cicutaria var. hubbyi, see Phacelia hubbyi
    ciliata (Great Valley phacelia)
    crenulata var. ambigua (Notchleaf phacelia)
    crenulata var. crenulata (Notchleaf phacelia)
    crenulata var. minutiflora (Smallflower notchleaf phacelia)
    cryptantha (Hiddenflower phacelia)
    curvipes (Curved-stem phacelia)
    davidsonii (Davidson's phacelia)
    distans (Common phacelia)
    douglasii (Douglas phacelia)
    egena (Rock phacelia)
    exilis (Lavender windows)
    fremontii (Fremont's phacelia)
    grandiflora (Large-flowered phacelia)
    hastata ssp. hastata (Timberline phacelia)
    hubbyi (Hubby's caterpillar phacelia)
    humilis var. dudleyi (Low phacelia)
    imbricata ssp. imbricata (Mountain phacelia)
    imbricata ssp. patula (Imbricate phacelia)
    insularis var. insularis (Northern Channel Islands phacelia)
    ivesiana (Ives' phacelia)
    longipes (Longstalk phacelia)
    minor (Canterbury bells)
    mohavensis (Mojave phacelia)
    mutabilis (Changeable phacelia)
    nashiana (Charlotte's phacelia)
    neglecta (Alkali phacelia)
    pachyphylla (Thick-leaved phacelia)
    parryi (Parry's phacelia)
    pedicellata (Pedicellate phacelia)
    perityloides var. perityloides (Panamint phacelia)
    ramosissima var. latifolia (Branching phacelia) * These two vars. are Phacelia ramosissima in JM2
    ramossisima var. ramossisima (Branching phacelia) * These two vars. are Phacelia ramosissima in JM2
    rotundifolia (Round-leaved phacelia)
    tanacetifolia (Tansy phacelia)
    vallis-mortae (Death Valley phacelia)
    viscida (Sticky phacelia)
Phalaris aquatica (Harding grass)*
Philadelphus microphyllus (Little-leaved mock orange)
Phleum alpinum (Mountain timothy)
Phlox
    austromontana (Southern mountain phlox)
    condensata (Condensed phlox)
    diffusa (Spreading phlox)
    dolichantha (Big Bear Valley phlox)
    gracilis, see Microsteris gracilis
    stansburyi (Stansbury phlox)
Pholisma
    arenarium (Scaly-stemmed sand plant)
    sonorae (Sand food)
Pholistoma
    auritum var. auritum (Fiesta flower)
    membranaceum (White fiesta flower)
Phoradendron
    bolleanum (Fir mistletoe)
    californicum (Desert mistletoe)
    juniperinum (Juniper mistletoe)
    libocedri (Incense-cedar mistletoe)
    macrophyllum (Big-leaf mistletoe)
    villosum (Oak mistletoe)
Phragmites australis (Common reed)
Phyllodoce breweri (Mountain heather)
Physalis
    crassifolia (Thick-leaved ground-cherry)
    hederifolia var. fendleri (Fendler's ground-cherry)
    lobata (Lobed ground-cherry)
Physaria
    kingii ssp. bernardina (San Bernardino Mountains bladderpod)
    kingii ssp. kingii (King's bladderpod)
    tenella (Palmer beadpod)
Physocarpus capitatus (Pacific ninebark)
Phytolacca americana (Pokeweed)*
Pickeringia
    montana var. montana (Chaparral pea)
    montana var. tomentosa (Woolly chaparral pea)
Picris echioides, see Helminthotheca echioides
Pilostyles thurberi (Thurber's stemsucker)
Pinus
    attenuata (Knobcone pine)
    contorta ssp. murrayana (Lodgepole pine)
    coulteri (Coulter pine)
    flexilis (Limber pine)
    halepensis (Aleppo pine)*
    jeffreyi (Jeffrey pine)
    lambertiana (Sugar pine)
    longaeva (Bristlecone pine)
    monophylla (Singleleaf pinyon pine)
    muricata (Bishop pine)
    ponderosa (Yellow pine)
    quadrifolia (Four-needle pinyon pine)
    sabiniana (Gray pine)
    torreyana (Torrey pine)
Piperia
    cooperi (Rein orchid)
    elongata (Dense-flowered rein orchid)
    transversa (Royal rein orchid)
    unalascensis (Alaska rein orchid)
Piptatherum miliaceum (Smilo grass)*
Plagiobothrys
    acanthocarpus (Adobe popcorn flower)
    arizonicus (Arizona popcorn flower)
    canescens (Valley popcorn flower)
    collinus var. fulvescens (California popcorn flower)
    fulvus (Tawny popcorn flower)
    hispidulus (Harsh popcorn flower)
    jonesii (Mojave popcorn flower)
    nothofulvus (Rusty-haired popcorn flower)
    tenellus (Slender popcorn flower)
    undulatus (Hooked popcorn flower)
Plantago
    arenaria (Sand plantain)*
    coronopus (Cut-leaf plantain)*
    elongata (Longleaf plantain)
    erecta (California plantain)
    lanceolata (English plantain)*
    major (Broad-leaf plantain)*
    ovata (Woolly plantain)
    patagonica (Patagonia plantain)
Platanthera
    dilatata var. leucostachys (White-flowered bog orchid)
    leucostachys, see Platanthera dilatata var. leucostachys
    sparsiflora (Sparse-flowered bog orchid)
Platanus racemosa (Western sycamore)
Platystemon californicus (Cream cups)
Plectritis ciliosa ssp. insignis (Long-spurred plectritis)
Pleiacanthus spinosus (Thorny skeleton-plant)
Pleuraphis rigida, see Hilaria rigida
Pleurocoronis pluriseta (Arrowleaf)
Pluchea
    odorata (Salt marsh fleabane)
    sericea (Arrow weed)
Poa
    atropurpurea (San Bernardino bluegrass)
    bulbosa (Bulbous bluegrass)*
    douglasii (Sand-dune bluegrass)
    fendleriana ssp. longiligula (Fendler's bluegrass)
    infirma (Weak bluegrass)*
    pratensis ssp. pratensis (Kentucky bluegrass)*
    secunda ssp. juncifolia (Rush bluegrass)
    secunda ssp. secunda (One-sided bluegrass)
Pogogyne nudiuscula (Otay Mesa mint)
Polemonium occidentale ssp. occidentale (Western sky pilot)
Polycarpon tetraphyllum (Four-leaf allseed)*
Polygala cornuta var. fishiae (Fish's milkwort)
Polygonum
    amphibium var. emersum (Swamp knotweed)
    arenastrum, see Polygonum aviculare ssp. depressum
    aviculare ssp. depressum (Common knotweed)*
    bistortoides, see Bistorta bistortoides
    capitatum (Himalayan smartweed)*
    douglasii ssp. douglasii (Douglas's knotweed)
    douglasii ssp. johnstonii (Douglas's knotweed)
    lapathifolium (Willow smartweed)
    punctatum (Water smartweed)
Polypodium
    californicum (California polypody)
    hesperium (Western polypody)
Polypogon
    interruptus (Ditch beard grass)*
    monspeliensis (Rabbitsfoot grass)*
    viridis (Green bentgrass)*
Polystichum
    imbricans ssp. curtum (Cliff sword fern)
    munitum (Western sword fern)
   scopulinum (Mountain holly fern)
Populus
    balsamifera ssp. trichocarpa (Black cottonwood)
    fremontii ssp. fremontii (Fremont's cottonwood)
    tremuloides (Quaking aspen)
Porophyllum gracile (Slender poreleaf)
Portulaca
    halimoides (Desert portulaca)
    oleracea (Purslane)*
Potamogeton diversifolius (Diverse-leaved pondweed)
Potentilla
    anserina ssp. anserina (Silverleaf cinquefoil)
    anserina ssp. pacifica (Silverweed)
    biennis (Biennial cinquefoil)
    glandulosa ssp. ewanii, see Drymocallis cuneifolia var. ewanii
    glandulosa ssp. glandulosa in part, see Drymocallis glandulosa var. wrangelliana (SoCO)
    glandulosa ssp. nevadensis, see Drymocallis lactea var. lactea
    glandulosa ssp. reflexa in part, see Drymocallis glandulosa var. reflexa (TR,PR)
    glandulosa ssp. reflexa in part, see Drymocallis glandulosa var. viscida (TR,PR)
    gracilis var. fastigiata (Slender cinquefoil)
    norvegica (Norwegian cinquefoil)*
    wheeleri (Wheeler's cinquefoil)
Prenanthella exigua (Bright white)
Prosopis
    glandulosa var. torreyana (Honey mesquite)
    pubescens (Screwbean mesquite)
Prunella vulgaris var. lanceolata (Self-heal)
Prunus
    andersonii (Desert peach)
    emarginata (Bitter cherry)
    eremophila (Desert prunus)
    fasciculata var. fasciculata (Desert almond)
    fremontii (Desert apricot)
    ilicifolia ssp. ilicifolia (Hollyleaf cherry)
    ilicifolia ssp. ilicifolia fruit (Hollyleaf cherry)
    ilicifolia ssp. lyonii (Catalina cherry)
    virginiana var. demissus (Western chokecherry)
Psathyrotes
    annua (Fan leaf)
    ramosissima (Turtleback)
Pseudognaphalium
    beneolens (Fragrant everlasting)
    biolettii (Two-tone everlasting)
    californicum (California everlasting)
    luteoalbum (Weedy cudweed)*
    microcephalum (Feltleaf everlasting)
    ramosissimum (Pink cudweed)
    stramineum (Cotton-batting plant)
    thermale (Slender everlasting)
Pseudostellaria jamesiana (Sticky starwort)
Pseudotsuga macrocarpa (Big-cone spruce)
Psilocarphus
    brevissimus var. brevissimus (Dwarf woollyheads)
    tenellus var. tenellus (Slender woollyheads)
Psilostrophe cooperi (Paperflower)
Psorothamnus
    arborescens var. minutifolius (Little-leaved Mojave indigo bush)
    arborescens var. simplicifolius (California indigo bush)
    emoryi (Emory indigo bush)
    polydenius (Dotted indigo bush)
    schottii (Schott's indigo bush)
    spinosus (Smoke tree)
Pteridium aquilinum var. pubescens (Bracken fern)
Pteris vittata (Ladder brake)*
Pterospora andromedea (Pinedrops)
Pterostegia drymarioides (Threadstem)
Pulicaria paludosa (Pulicaria)*
Purshia
    mexicana var. stansburyana (Cliff rose)
    tridentata var. glandulosa (Desert bitterbrush)
Pycnanthemum californicum (Mountain mint)
Pyrola
    asarifolia ssp. asarifolia (Bog wintergreen)
    picta (White-veined wintergreen)
Pyrrocoma uniflora var. gossypina (Bear Valley pyrrocoma)