My sources for all the plants on my Washington Natives list are:

1. Lady Bird Johnson Wildflower Center
2. Central Washington Native Plants
3. UW Herbarium at the Burke
4. Garden Guide
5. Washington Native Plant Society
6. USDA Plants Database

• Abies amabilis - Cascade fir, Lovely fir, Pacific silver fir, White fir, amabilis fir
• Abies grandis - Giant fir, Grand fir, lowland or lowland white fir, stinking fir
• Abies lasiocarpa - Subalpine fir, alpine fir, balsam or white balsam fir
• Abies procera syn Abies nobilis - Noble fir
• Abronia fragrans syn Abronia fragrans var. glaucescens - heart's-delight
• Abronia latifolia - Coastal sand verbena, Yellow Sand Verbena
• Abronia mellifera - White sand verbena, honey-scented sand-verbena
• Abronia umbellata - Beach Sand Verbena, Pink sand verbena
• Acer circinatum - Oregon vine maple, Vine maple
• Acer glabrum - Rocky Mountain maple
• Acer macrophyllum - Big-leaf maple, Bigleaf maple
• Achillea millefolium - Common yarrow, Milfoil, Western yarrow, Yarrow
• Achlys californica - deer's-foot
• Achlys triphylla - Sweet after death, Vanilla leaf, deer's-foot
• Achnatherum hendersonii syn Oryzopsis hendersonii, Stipa hendersonii - Henderson's needlegrass, Henderson's rice grass
• Achnatherum hymenoides syn Eriocoma cuspidata, Oryzopsis hymenoides, Stipa hymenoides - Indian Millet, Indian rice grass, Sandgrass
• Achnatherum nelsonii ssp. dorei - Columbia needlegrass, Dore's needlegrass
• Achnatherum occidentale ssp. occidentale syn Stipa occidentalis - Western needlegrass
• Achnatherum richardsonii - Richardson's needlegrass
• Aconitum columbianum - Columbian monkshood
• Acorus americanus syn Acorus calamus var. americanus - Sweetflag, several-vein sweetflag
• Acorus calamus - Calamus, Single-vein sweetflag, Sweet flag
• Actaea elata syn Cimicifuga elata - Tall bugbane
• Actaea rubra - Red baneberry
• Actaea rubra ssp. arguta - Red baneberry
• Adenocaulon bicolor - American trailplant, Pathfinder
• Adiantum aleuticum syn Adiantum pedatum, Adiantum pedatum ssp. aleuticum, Adiantum pedatum ssp. calderi, Adiantum pedatum ssp. subpumilum, Adiantum pedatum var. aleuticum, Adiantum pedatum var. subpumilum - Aleutian Maidenhair Fern, Northern Maidenhair Fern
• Agastache foeniculum - Blue giant hyssop, Fragrant giant hyssop, Lavender hyssop
• Agastache occidentalis - western giant-hyssop
• Agastache urticifolia - Nettle-leaf Horsemint, Nettleleaf giant hyssop
• Ageratina occidentalis - Western snakeroot, Western thoroughwort
• Agoseris aurantiaca - Orange agoseris, slender agoseris
• Agoseris elata syn Stylopappus elatus - tall agoseris, tall goat-chicory
• Agoseris glauca - Pale agoseris, Pale Mountain Dandelion, field agoseris
• Agoseris grandiflora syn Agoseris laciniata, Agoseris plebeja, Troximon grandiflorum - large-flowered agoseris, large-flower goat-chicory
• Agoseris heterophylla - Annual agoseris
• Agrimonia gryposepala - Agrimony, Tall hairy agrimony
• Agrostis capillaris syn Agrostis sylvatica, Agrostis tenuis, Agrostis tenuis var. aristata, Agrostis tenuis var. hispida, Agrostis tenuis var. pumila - colonial bentgrass
• Agrostis exarata syn Agrostis aenea, Agrostis alaskana , Agrostis ampla, Agrostis asperifolia, Agrostis exarata ssp. exarata, Agrostis exarata ssp. exarata var. exarata, Agrostis exarata ssp. exarata var. monolepsis, Agrostis exarata ssp. minor, Agrostis exarata var. minor, Agrostis exarata var. monolepis, Agrostis exarata var. pacifica, Agrostis exarata var. purpurascens, Agrostis longiligula, Agrostis longiligula var. australis, Agrostis melaleuca, Agrostis microphylla var. major - Spike bentgrass, Spike red top, Spiked bent grass
• Agrostis gigantea syn Agrostis alba, Agrostis alba var. alba, Agrostis gigantea var. dispar, Agrostis nigra, Agrostis stolonifera ssp. gigantea, Agrostis stolonifera var. major - redtop, black bentgrass
• Agrostis mertensii - Northern bentgrass
• Agrostis pallens syn Agrostis diegoensis, Agrostis lepida, Agrostis pallens var. vaseyi -
  seashore bentgrass
• Agrostis perennans - Autumn bentgrass, Upland bentgrass
• Agrostis scabra - Fly-away grass, Rough bentgrass, Ticklegrass
• Alchemilla occidentalis Syn A. cuneifolia, A. occidentalis, Aphanes occidentalis - Western lady's-mantle, Parsley piert, colickwort, field lady's mantle, parsley breakstone
• Alisma gramineum syn Alisma geyeri, Alisma gramineum var. angustissimum, Alisma gramineum var. geyeri, Alisma gramineum var. gramineum, Alisma gramineum var. graminifolium, Alisma gramineum var. wahlenbergii, Alisma lanceolatum - narrow-leaf water-plantain, grass-leaved water-plantain
• Alisma triviale syn Alisma brevipes, Alisma plantago-aquatica ssp. brevipes, Alisma plantago-aquatica var. americanum, Alisma plantago-aquatica var. brevipes - Northern water plantain
• Allium acuminatum syn Allium acuminatum var. cuspidatum - Tapertip onion
• Allium amplectens syn Allium attenuifolium, Allium monospermum, Allium occidentale - Narrowleaf onion
• Allium campanulatum - Dusky onion, rosy Sierra onion
• Allium cernuum - Nodding onion
• Allium constrictum syn Allium douglasii var. constrictum - Grand Coulee onion
• Allium crenulatum syn Allium cascadense, Allium vancouverense, Allium watsonii - Olympic onion, scalloped onion
• Allium dictuon - Blue Mountain onion
• Allium douglasii syn Allium douglasii var. douglasii - Douglas' onion
• Allium fibrillum syn Allium collinum - Cuddy Mountain onion, fringed onion
• Allium macrum syn Allium equicaeleste - Rock onion
• Allium nevii syn Allium douglasii var. nevii - Nevius' garlic
• Allium robinsonii - Robinson's onion
• Allium schoenoprasum - Wild chives
• Allium scilloides - fragile onion, Scilla-like onion
• Allium textile - Textile onion
• Allium tolmiei - Tolmie's onion
• Allium validum - Pacific onion, Swamp onion, Tall swamp onion foxtail
• Allotropa virgata - sugarstick, candystick
• Alnus incana - Gray alder, Speckled alder, mountain alder
• Alnus rhombifolia syn Alnus rhombifolia Nutt. var. bernardina - White alder, California alder
• Alnus rubra syn Alnus oregona, Alnus oregona var. pinnatisecta - Red alder, Oregon alder
• Alnus viridis - Green alder, Siberian alder
• Alopecurus geniculatus - water foxtail, water fescue
• Ambrosia acanthicarpa syn Franseria acanthicarpa, Gaertneria acanthicarpa - flat-spine bur ragweed, bur ragweed, annual bursage
• Ambrosia chamissonis Syn Ambrosia chamissonis var. bipinnatisecta, Franseria chamissonis, Franseria chamissonis ssp. bipinnatisecta, Franseria chamissonis var. bipinnatisecta - Silver bursage, beach bur, silver burr ragweed, cutleaf beach bur
• Ambrosia psilostachya syn Ambrosia californica, Ambrosia coronopifolia, Ambrosia cumanensis, Ambrosia psilostachya var. californica, Ambrosia psilostachya var. coronopifolia, Ambrosia psilostachya var. lindheimeriana, Ambrosia rugelii - Cuman ragweed, Western Ragweed, perennial ragweed
• Amelanchier alnifolia - Juneberry, Saskatoon service-berry, Western serviceberry
• Amelanchier utahensis - Utah serviceberry
• Ammannia robusta - Grand redstem
• Amsinckia lycopsoides syn Amsinckia barbata, Benthamia lycopsoides - Tarweed fiddleneck, bugloss fiddleneck
• Amsinckia menziesii - Menzies' fiddleneck, rancher's fiddleneck, fireweed fiddleneck, small-flowered fiddleneck
• Amsinckia menziesii var. intermedia syn Amsinckia arizonica, Amsinckia demissa, Amsinckia echinata, Amsinckia intactilis, Amsinckia intermedia, Amsinckia intermedia var. echinata, Amsinckia microphylla, Amsinckia nana Suksdorf, Amsinckia rigida - coast fiddleneck, common fiddleneck, fiddleneck
• Amsinckia menziesii var. menziesii syn Amsinckia hispida, Amsinckia idahoensis, Amsinckia micrantha, Amsinckia parviflora, Amsinckia retrorsa, Amsinckia rugosa, Echium menziesii - Menzies' fiddleneck
• Amsinckia spectabilis - Sea-side amsinckia
• Amsinckia tessellata - Bristly fiddleneck, tessellate fiddleneck
• Anagallis minima syn Centunculus minimus - Chaffweed
• Anaphalis margaritacea syn Anaphalis margaritacea var. angustior, Anaphalis margaritacea var. intercedens, Anaphalis margaritacea var. occidentalis, Anaphalis margaritacea var. revoluta, Anaphalis margaritacea var. subalpina, Anaphalis occidentalis, Gnaphalium margaritaceum - Pearly-everlasting, Western pearly everlasting
• Andromeda polifolia - Bog rosemary
• Androsace septentrionalis - Northern Fairy Candelabra, Pygmyflower rockjasmine
• Anemone deltoidea - three-leaf anemone, Columbian windflower
• Anemone drummondii - Alpine Anemone
• Anemone lyallii syn Anemone nemorosa var. lyallii, Anemone quinquefolia var. lyallii - Lyall's anemone, little mountain anemone or thimbleweed
• Anemone multifida - Cut-leaf, Pacific anemone anemone, Early thimbleweed, Pacific anemone, Red windflower
• Anemone nuttalliana syn Pulsatilla patens - American Pasqueflower, Eastern pasqueflower, Cutleaf anemone
• Anemone occidentalis - western pasqueflower
• Anemone oregana - Blue windflower, Oregon Anemone, western wood anemone
• Anemone parviflora - Smallflowered anemone, northern anemone
• Anemone patens - prairie pasqueflower
• Anemone piperi - Piper's anemone, Piper's windflower
• Angelica arguta syn Angelica lyallii - Lyall's angelica, sharptooth angelica
• Angelica canbyi - Canby's angelica
• Angelica genuflexa - Kneeling angelica
• Angelica hendersonii syn Angelica tomentosa var. hendersonii - Henderson's angelica, Seaside Angelica
• Angelica lucida syn Coelopleurum actaeifolium, Coelopleurum gmelinii , Coelopleurum lucidum, Coelopleurum lucidum ssp. gmelinii - Seacoast angelica, sea-watch
• Antennaria anaphaloides syn Antennaria pulcherrima ssp. anaphaloides, Antennaria pulcherrima var. anaphaloides - pearly pussytoes, tall pussytoes
• Antennaria dimorpha syn Antennaria dimorpha var. integra, Antennaria dimorpha var. latisquama, Antennaria dimorpha var. macrocephala, Antennaria latisquama, Antennaria macrocephala, Gnaphalium dimorphum - Low pussytoes, cushion pussytoes
• Antennaria flagellaris syn Antennaria dimorpha var. flagellaris - whip pussytoes, stoloniferous everlasting, flagellate pussytoes
• Antennaria howellii - Howell's pussytoes
• Antennaria lanata syn Antennaria carpathica var. lanata - Woolly pussytoes, woolly everlasting
• Antennaria luzuloides - Woodrush pussytoes, silvery brown everlasting
• Antennaria media syn Antennaria alpina, Antennaria alpina var. media, Antennaria austromontana, Antennaria candida, Antennaria densa, Antennaria gormanii, Antennaria modesta, Antennaria mucronata - Rocky Mountain Pussytoes, alpine pussytoes
• Antennaria microphylla syn Antennaria bracteosa, Antennaria nitida, Antennaria parvifolia var. bracteosa, Antennaria rosea var. nitida, Antennaria solstitialis - little-leaf pussytoes, small-leaf pussytoes
• Antennaria parvifolia syn Antennaria aprica, Antennaria aprica var. minuscula, Antennaria aureola, Antennaria holmii, Antennaria latisquamea, Antennaria minuscula, Antennaria obtusata, Antennaria pumila, Antennaria recurva, Antennaria rhodanthus - little-leaf pussytoes, Small-leaf pussytoes
• Antennaria racemosa syn Antennaria petasites, Antennaria piperi - Raceme pussytoes, slender everlasting, Hooker's pussytoes
• Antennaria rosea - Rosy pussytoes, rosy everlasting
• Antennaria stenophylla syn Antennaria alpina var. stenophylla, Antennaria leucophaea - Narrowleaf pussytoes
• Antennaria umbrinella syn Antennaria aizoides, Antennaria flavescens, Antennaria reflexa - umber pussytoes, brown everlasting, brown-bract pussytoes
• Apocynum androsaemifolium syn Apocynum ambigens, Apocynum androsaemifolium ssp. pumilum, Apocynum androsaemifolium var. androsaemifolium, Apocynum androsaemifolium var. glabrum, Apocynum androsaemifolium var. griseum, Apocynum androsaemifolium var. incanum, Apocynum androsaemifolium var. intermedium, Apocynum androsaemifolium var. pumilum, Apocynum androsaemifolium var. tomentellum, Apocynum androsaemifolium var. woodsonii, Apocynum pumilum, Apocynum pumilum var. rhomboideum, Apocynum scopulorum - Bitterroot, Flytrap dogbane, Spreading dogbane
• Apocynum cannabinum syn Apocynum cannabinum var. angustifolium, Apocynum cannabinum var. glaberrimum, Apocynum cannabinum var. greeneanum, Apocynum cannabinum var. hypericifolium, Apocynum cannabinum var. nemorale, Apocynum cannabinum var. pubescens, Apocynum cannabinum var. suksdorfii, Apocynum hypericifolium, Apocynum pubescens, Apocynum sibiricum, Apocynum sibiricum var. cordigerum, Apocynum sibiricum var. farwellii, Apocynum sibiricum var. salignum, Apocynum suksdorfii, Apocynum suksdorfii var. angustifolium - Dogbane, Hemp dogbane, Indianhemp
• Apocynum ×floribundum syn Apocynum jonesii, Apocynum medium, Apocynum medium var. floribundum, Apocynum medium var. leuconeuron, Apocynum medium var. lividum, Apocynum medium var. sarniense, Apocynum medium var. vestitum, Apocynum milleri - hybrid dogbane, intermediate dogbane
• Aquilegia flavescens - Yellow columbine
• Aquilegia formosa syn Aquilegia formosa var. communis, Aquilegia formosa var. fosteri, Aquilegia formosa var. hypolasia, Aquilegia formosa var. megalantha, Aquilegia formosa var. pauciflora, Aquilegia formosa var. truncata, Aquilegia formosa var. wawawensis, Aquilegia mohavensis, Aquilegia shockleyi - Crimson columbine, Scarlet columbine, Western columbine, Sitka columbine
• Arabis crucisetosa - wetsoil rockcress, crosshaired rockcress
• Arabis cusickii - Cusick's rockcress
• Arabis drummondii - Drummond's rockcress
• Arabis eschscholtziana syn Arabis hirsuta ssp. eschscholtziana, Arabis hirsuta var. eschscholtziana - Eschscholtz's hairy rockcress, Pacific coast rockcress
• Arabis glabra syn Arabis glabra var. furcatipilis, Turritis glabra - tower rockcress, tower mustard
• Arabis hirsuta - Hairy rockcress
• Arabis holboellii - Holboell's rockcress
• Arabis kamchatica - Kamchatica rockcress
• Arabis lemmonii - Lemmon's rockcress
• Arabis lyallii - Lyall's rockcress
• Arabis microphylla - littleleaf rockcress
• Arabis sparsiflora - Sicklepod rockcress
• Arabis ×divaricarpa - Spreadingpod rockcress
• Aralia nudicaulis - Wild sarsaparilla
• Arbutus menziesii - Laurelwood, Oregon laurel, Pacific madrone
• Arceuthobium americanum - American dwarf mistletoe, lodgepole pine dwarf-mistletoe
• Arceothobium campylopodum syn Arceuthobium campylopodum f. campylopodum - Western Dwarf Mistletoe
• Arceuthobium douglasii - Dwarf mistletoe, Douglas-fir Dwarf Mistletoe
• Arctostaphylos columbiana syn Arctostaphylos columbiana var. tracyi, Arctostaphylos tracyi - Hairy manzanita, bristly manzanita
• Arctostaphylos nevadensis syn Arctostaphylos pungens ssp. nevadensis - Pinemat manzanita
• Arctostaphylos patula syn Arctostaphylos acutifolia, Arctostaphylos parryana var. pinetorum, Arctostaphylos patula ssp. platyphylla, Arctostaphylos patula var. coalescens - Green-leaf manzanita
• Arctostaphylos uva-ursi Syn Arctostaphylos adenotricha, Arctostaphylos uva-ursi ssp. adenotricha, Arctostaphylos uva-ursi ssp. coactilis, Arctostaphylos uva-ursi ssp. longipilosa, Arctostaphylos uva-ursi ssp. monoensis, Arctostaphylos uva-ursi ssp. stipitata Arctostaphylos uva-ursi var. adenotricha, Arctostaphylos uva-ursi var. coactilis, Arctostaphylos uva-ursi var. leobreweri, Arctostaphylos uva-ursi var. marinensis, Arctostaphylos uva-ursi var. pacifica, Arctostaphylos uva-ursi var. stipitata, Arctostaphylos uva-ursi, Uva-Ursi uva-ursi - Bearberry, Kinnikinnick, Pinemat Manzanita, Carillo, Mealberry, Mountain Box, Mountain Cranberry, Sandberry, Sagackhomi, Bear's Berry and Arberry, Hog Cranberry
• Arenaria capillaris - Beautiful Sandwort Slender mountain sandwort
• Arenaria aculeata syn Arenaria congesta var. aculeata, Arenaria fendleri var. aculeata, Arenaria pumicola var. californica, Arenaria salmonensis, Eremogone aculeata -
  prickly sandwort, needle-leaf sandwort
• Arenaria capillaris - slender mountain sandwort, thread-leaved sandwort
• Arenaria congesta - Ballhead sandwort
• Arenaria franklinii - Franklin's sandwort
• Argentina egedii syn Potentilla anserina ssp. egedii, Potentilla anserina ssp. pacifica, Potentilla anserina var. grandis, Potentilla anserina var. lanata, Potentilla anserina var. rolandii, Potentilla egedii, Potentilla egedii ssp. grandis, Potentilla egedii var. grandis, Potentilla pacifica, Potentilla rolandii - Pacific silverweed
• Aristida purpurea - Purple three-awn, Red threeawn
• Aristida purpurea var. longiseta - Fendler threeawn, Red threeawn
• Armeria maritima Syn Armeria elongata, Armeria vulgaris, Statice armeria, Statice maritima, Armeria arctica, Armeria labradorica, Armeria labradorica var. submutica, Armeria maritima ssp. arctica, Armeria maritima ssp. labradorica, Armeria maritima ssp. maritima, Armeria maritima ssp. purpurea, Armeria maritima ssp. sibirica, Armeria maritima subsp. elongata, Armeria maritima var. labradorica, Armeria maritima var. pubescens, Armeria maritima var. purpurea, Armeria maritima var. sibirica, Armeria scabra, Armeria scabra ssp. Siberica - Thrift seapink
• Arnica amplexicaulis syn Arnica amplexicaulis ssp. genuina, Arnica amplexicaulis ssp. prima, Arnica amplexicaulis var. amplexicaulis, Arnica amplexicaulis var. piperi, Arnica amplexicaulis var. prima, Arnica amplexifolia, Arnica mollis Hvar. aspera - Clasping arnica
• Arnica chamissonis - Chamisso arnica
• Arnica cordifolia syn Arnica cordifolia ssp. genuina, Arnica cordifolia var. cordifolia, Arnica cordifolia var. humilis, Arnica cordifolia var. pumila, Arnica cordifolia var. whitneyi, Arnica hardinae, Arnica humilis, Arnica paniculata, Arnica whitneyi - Heart-leaf leopardbane, Heartleaf arnica
• Arnica discoidea syn Arnica discoidea var. alata, Arnica discoidea var. eradiata, Arnica grayi, Arnica parviflora, Arnica parviflora ssp. alata - rayless arnica, rayless leopardbane
• Arnica fulgens - Foothill arnica, orange arnica, shining leopardbane
• Arnica gracilis syn Arnica latifolia var. gracilis - slender arnica, small-head arnica, slender leopardbane
• Arnica latifolia syn Arnica latifolia var. angustifolia, Arnica latifolia var. latifolia - Broadleaf arnica, Daffodil leopardbane, Mountain arnica
• Arnica longifolia syn Arnica longifolia ssp. genuina, Arnica longifolia ssp. myriadenia - Spearleaf arnica, seep spring arnica, longleaf arnica, spear-leaf leopardbane
• Arnica mollis syn Arnica mollis var. silvatica - Hairy arnica, cordilleran arnica, cordilleran leopardbane
• Arnica nevadensis syn Arnica tomentella - Nevada arnica, Sierra arnica, Sierran leopardbane
• Arnica parryi syn Arnica parryi var. parryi - Parry's arnica
• Arnica rydbergii - Rydberg's arnica
• Arnica sororia syn Arnica fulgens var. sororia - twin arnica, bunch arnica, twin leopardbane
• Artemisia arbuscula - little sagebrush, low sagebrush
• Artemisia campestris - Field sagewort
• Artemisia douglasiana - Douglas mugwort Douglas' sagewort
• Artemisia dracunculus syn Artemisia dracunculoides, Artemisia dracunculoides var. dracunculina, Artemisia dracunculus ssp. glauca, Artemisia dracunculus var. dracunculus, Artemisia dracunculus var. glauca, Artemisia glauca, Artemisia glauca var. dracunculina, Oligosporus dracunculus, Oligosporus dracunculus ssp. dracunculinus, Oligosporus dracunculus ssp. glaucus - dragon sagewort, tarragon, dragon wormwood
• Artemisia frigida - Fringed sage, Prairie sagebrush, Prairie sagewort
• Artemisia lindleyana syn Artemisia prescottiana - Columbia River wormwood, riverbank wormwood, Columbia river sagewort, Columbia river mugwort
• Artemisia ludoviciana - Cudweed sagewort, Gray sagewort, Louisiana sagewort, Louisiana wormwood, Mugwort wormwood, Prairie sage, White sagebrush
• Artemisia michauxiana syn Artemisia vulgaris ssp. michauxiana - mugwort, lemon sagewort
• Artemisia rigida syn Artemisia trifida var. rigida, Seriphidium rigidum - scabland sagebrush, stiff sagebrush
• Artemisia stelleriana - Dusty Miller Oldwoman
• Artemisia suksdorfii - coastal wormwood, coastal mugwort, Suksdorf's sagewort
• Artemisia tridentata - Big sagebrush, Great Basin sagebrush, spiked sagebrush
• Aruncus dioicus syn Aruncus sylvester - Goatsbeard, Bride's Feathers
• Asarum caudatum - British Columbia wildginger, Long-tail wild ginger, Wild Ginger
• Asclepias cryptoceras - pallid milkweed
• Asclepias fascicularis syn Asclepias mexicana - Mexican whorled milkweed, Narrowleaf milkweed
• Asclepias speciosa syn Asclepias giffordii - Showy milkweed
• Aspidotis densa syn Cheilanthes siliquosa, Cryptogramma densa, Onychium densum, Pellaea densa - Cliff brake, Indian's dream, Rock brake, Oregon cliff brake, podfern
• Asplenium trichomanes - Maidenhair spleenwort
• Asplenium trichomanes-ramosum syn Asplenium viride - Brightgreen spleenwort, green spleenwort
• Astragalus agrestis syn Astragalus danicus var. dasyglottis, Astragalus dasyglottis, Astragalus goniatus, Astragalus hypoglottis - Field Milk-vetch, Purple milkvetch
• Astragalus alpinus - Alpine milkvetch
• Astragalus arthurii syn Astragalus arthuri - waha milk-vetch, Arthur's milk-vetch
• Astragalus canadensis - Canadian milk-vetch, Milk vetch
• Astragalus cicer - cicer milk-vetch, chickpea milk-vetch
• Astragalus columbianus - Columbian milk-vetch
• Astragalus conjunctus - Idaho milk-vetch, stiff milk-vetch
• Astragalus cottonii syn Astragalus australis var. cottonii, Astragalus australis var. olympicus - Cotton's milk-vetch
• Astragalus cusickii - Cusick's milk-vetch
• Astragalus geyeri - Geyer's milk-vetch
• Astragalus hoodianus syn Astragalus conjunctus var. oxytropidoides, Astragalus reventus var. oxytropidoides, Cnemidophacos knowlesianus - Hood River milk-vetch
• Astragalus inflexus - Bent milkvetch
• Astragalus kentrophyta - Spiny milkvetch
• Astragalus leibergii syn Astragalus arrectus var. leibergii - Leiberg's milk-vetch
• Astragalus lentiginosus - Freckled milkvetch, specklepod milk-vetch
• Astragalus lyallii - Lyall's milk-vetch
• Astragalus microcystis - dwarf milk-vetch, lesser-bladder milk-vetch
• Astragalus purshii - Woollypod milkvetch
• Astragalus misellus - pauper milk-vetch
• Astragalus miser - timber milk-vetch, weedy milk-vetch
• Astragalus pulsiferae - Ames' milk-vetch
• Astragalus purshii - Wooly Milk-Vetch, woolly-pod milk-vetch
• Astragalus reventiformis syn Astragalus reventus var. canbyi - Yakima milk-vetch
• Astragalus riparius - woodyroot milk-vetch, Piper's milk-vetch
• Astragalus robbinsii - Robbins' milkvetch
• Astragalus sclerocarpus - woody-pod milk-vetch, stalked-pod milk-vetch
• Astragalus sinuatus syn Astragalus whitedii - Whited's milk-vetch
• Astragalus spaldingii - Spalding's milk-vetch
• Astragalus speirocarpus - threadstalk milk-vetch, medic milk-vetch, curve-pod milk-vetch, spiral-pod milk-vetch
• Astragalus succumbens - Columbia milk-vetch, sprawling milk-vetch, crouching milk-vetch
• Astragalus tweedyi - Tweedy's milk-vetch
• Astragalus whitneyi - Balloonpod Milk-Vetch, balloon milk-vetch
• Athyrium americanum syn Athyrium alpestre, Athyrium alpestre ssp. americanum, Athyrium alpestre var. americanum, Athyrium alpestre var. gaspense, Athyrium distentifolium, Athyrium distentifolium ssp. americanum, Athyrium distentifolium var. americanum - alpine ladyfern, American alpine lady fern
• Athyrium filix-femina - Common ladyfern, Lady fern, Subarctic lady fern
• Athysanus pusillus syn Athysanus pusillus var. glabrior, Thysanocarpus pusillus - common sandweed
• Atriplex canescens - Chamiso, Four-wing saltbush, Wingscale, hoary saltbush
• Atriplex gmelinii syn Atriplex gmelinii var. zosterifolia, Atriplex patula ssp. obtusa, Atriplex patula var. obtusa, Atriplex patula var. zosterifolia - Gmelin's saltbush
• Atriplex littoralis - Grassleaf orache
• Atriplex patula Syn Atriplex patula var. bracteata auct. non Westerlund, Atriplex patula var. erecta, Atriplex patula var. japonica, Atriplex patula var. patula, Atriplex patula var. hastata, Atriplex patula ssp. patula, Atriplex glabriuscula auct. non Edmondston - Orache, spear saltbush, spear orach, spear-scale, spreading orache, Halberd-leaf Orache, Fat-Hen Saltbush, spear oracle
• Atriplex prostrata - Triangle orache
• Atriplex spinosa syn Grayia spinosa - Spiny Hopsage
• Atriplex subspicata - Saline saltbush
• Azolla filiculoides - Pacific mosquito-fern, duckweed fern, large mosquito-fern
• Azolla mexicana - Mexican mosquitofern, Mexican water-fern

• Balsamorhiza careyana - Carey's Balsamroot
• Balsamorhiza careyana var. intermedia × Balsamorhiza hookeri var. lagocephala - hybrid balsamroot
• Balsamorhiza deltoidea - Deltoid balsamroot, Puget balsamroot
• Balsamorhiza hookeri - Hairy balsamroot, Hooker's balsamroot
• Balsamorhiza hookeri var. lagocephala × Balsamorhiza sagittata - hybrid balsamroot
• Balsamorhiza incana - Hoary balsamroot, woolly balsamroot
• Balsamorhiza rosea - rosy balsamroot
• Balsamorhiza sagittata - Arrow-leaf balsamroot
• Balsamorhiza serrata - serrate balsamroot, toothed balsamroot
• Barbarea orthoceras syn Barbarea americana, Barbarea orthoceras var. dolichocarpa - American yellowrocket, American wintercress
• Beckmannia syzigachne syn Beckmannia eruciformis, Beckmannia eruciformis ssp. baicalensis, Beckmannia eruciformis var. uniflora, Beckmannia syzigachne ssp. baicalensis, Beckmannia syzigachne var. uniflora - American sloughgrass
• Berula erecta syn Berula erecta (Huds.) Cov. var. incisa (Torr.) Cronq.
  Berula incisa (Torr.) G.N. Jones
  Berula pusilla Fern.
  Siella erecta - Cutleaf Waterparsnip, Berula, stalky berula
• Besseya rubra syn Synthyris rubra - red besseya, red coraldrops
• Betula nana syn Betula exilis, Betula glandulosa, Betula glandulosa var. glandulosa, Betula glandulosa var. hallii, Betula glandulosa var. sibirica, Betula michauxii, Betula nana ssp. exilis, Betula nana var. sibirica, Betula terrae-novae - Dwarf birch, Swamp birch, resin birch
• Betula occidentalis syn Betula beeniana, Betula fontinalis, Betula occidentalis var. inopina, Betula occidentalis var. occidentalis, Betula papyrifera ssp. occidentalis, Betula papyrifera var. occidentalis - Mountain birch, Water birch, river birch, red birch
• Betula papyrifera - Paper birch
• Betula pumila - Bog birch
• Bidens beckii - Beck's watermarigold
• Bidens cernua syn Bidens cernua var. dentata, Bidens cernua var. elliptica, Bidens cernua var. integra, Bidens cernua var. minima, Bidens cernua var. oligodonta, Bidens cernua var. radiata, Bidens glaucescens - Bur marigold, Nodding beggartick, Nodding bur marigold, Sticktight
• Bidens frondosa syn Bidens frondosa L. var. anomala, Bidens frondosa var. caudata, Bidens frondosa var. pallida, Bidens frondosa var. stenodonta - Devil's beggartick, Spanish Needles, leafy beggarticks, sticktight, devil's pitchfork
• Bidens vulgata syn Bidens frondosa var. puberula, Bidens puberula, Bidens vulgata var. puberula, Bidens vulgata var. schizantha - Big devils beggartick, tall beggarticks, western sticktight
• Blechnum spicant syn Blechnum spicant ssp. nipponicum, Blechnum spicant var. elongatum, Lomaria spicant, Osmunda spicant, Struthiopteris spicant - Deer fern
• Blepharipappus scaber - Rough eyelashweed
• Bolandra oregana syn Bolandra oregana var. imnahaensis - northern false coolwort
• Bolboschoenus maritimus syn Schoenoplectus maritimus, Scirpus maritimus - salt-marsh bulrush
• Boschniakia hookeri - Vancouver Groundcone, small groundcone, poque
• Botrychium ascendens - trianglelobe moonwort, upswept moonwort
• Botrychium campestre - Iowa moonwort
• Botrychium crenulatum syn Botrychium dusenii - scalloped moonwort, dainty moonwort
• Botrychium lanceolatum - lanceleaf moonwort, Lanceleaf grapefern
• Botrychium lineare - slender moonwort, Narrowleaf grapefern
• Botrychium lunaria syn Botrychium lunaria var. lunaria, Botrychium lunaria var. onondagense, Botrychium onondagense - Common moonwort
• Botrychium michiganense - Michigan moonwort
• Botrychium minganense syn Botrychium lunaria ssp. minganense, Botrychium lunaria var. minganense - Mingan moonwort
• Botrychium montanum - mountain moonwort, western goblin
• Botrychium multifidum syn Botrychium californicum, Botrychium coulteri, Botrychium matricariae, Botrychium multifidum ssp. californicum, Botrychium multifidum ssp. coulteri, Botrychium multifidum ssp. silaifolium, Botrychium multifidum var. californicum, Botrychium multifidum var. coulter, Botrychium multifidum var. intermedium, Botrychium multifidum var. silaifolium, Botrychium silaifolium, Botrychium silaifolium var. coulteri - Leathery grapefern
• Botrychium paradoxum - paradox moonwort, peculiar or two-spiked moonwort
• Botrychium pedunculosum - stalked moonwort
• Botrychium pinnatum syn Botrychium boreale, Botrychium boreale ssp. obtusilobum, Botrychium boreale var. obtusilobum - northern moonwort, northwestern or St. John's moonwort
• Botrychium simplex syn Botrychium simplex ssp. typicum, Botrychium simplex var. compositum, Botrychium simplex var. laxifolium, Botrychium simplex var. tenebrosum, Botrychium tenebrosum - least moonwort, Little grapefern
• Botrychium virginianum syn Botrychium virginianum ssp. europaeum, Botrychium virginianum var. europaeum - Rattlesnake fern, rattlesnake grapefern, common or virginia grapefern
• Boykinia intermedia syn Boykinia major, Boykinia major var. intermedia, Boykinia major var. major - Sierra brookfoam, greater boykinia
• Boykinia occidentalis syn Boykinia elata, Boykinia vancouverensis - Coast Boykinia, Coastal brookfoam
• Brasenia schreberi syn Brasenia peltata - Watershield
• Brickellia grandiflora syn Brickellia grandiflora var. petiolaris, Coleosanthus grandiflorus - tasselflower brickellbush, large flowered tasselflower, large flowered thoroughwort
• Brickellia oblongifolia - Mojave brickellbush, narrowleaf brickellia
• Brodiaea coronaria - Crown brodiaea, harvest brodiaea, bluedick brodiaea
• Brodiaea douglasii - Douglas' Brodiaea, Wild Hyacinth
• Bromus carinatus syn Bromus carinatus var. californicus, Bromus carinatus var. carinatus, Bromus carinatus var. hookerianus, Bromus laciniatus, Ceratochloa carinata - California brome
• Bromus ciliatus - Fringed brome
• Bromus inermis - Smooth brome, Pumpelly's brome grass, Hungarian bromegrass, awnless brome
• Bromus marginatus syn Bromus breviaristatus, Bromus carinatus var. linearis, Bromus marginatus var. breviaristatus, Bromus marginatus var. latior, Bromus marginatus var. seminudus, Bromus sitchensis var. marginatus, Ceratochloa marginata, Ceratochloa marginata - Mountain brome
• Bromus pacificus syn Bromus pacificus - Pacific brome
• Bromus sitchensis Syn Bromus sitchensis var. aleutensis, Bromus sitchensis var. marginatus, Bromus sitchensis var. sitchensis - Alaska brome, Sitka Brome
• Bromus squarrosus - corn brome
• Bromus vulgaris syn Bromopsis vulgaris, Bromus vulgaris var. eximius, Bromus vulgaris var. robustus, Bromus vulgaris var. vulgaris - Narrow-leaf brome, Columbia brome

• Cacaliopsis nardosmia syn Cacalia nardosmia, Cacalia nardosmia var. glabrata, Cacaliopsis nardosmia var. glabrata, Luina nardosmia, Luina nardosmia var. glabrata - Silvercrown
• Cakile edentula - American searocket
• Cakile maritima syn Cakile cakile - European searocket
• Calamagrostis canadensis - Bluejoint, bluejoint reedgrass
• Calamagrostis purpurascens - Purple reedgrass
• Calamagrostis rubescens syn Calamagrostis fasciculata - Pinegrass
• Calamagrostis stricta - Slimstem reedgrass, narrow-spiked reedgrass
• Calamagrostis tweedyi - Tweedy's reedgrass, Cascade reedgrass
• Calandrinia ciliata syn Calandrinia ciliata var. menziesii - Fringed redmaids, Redmaids
• Callitriche hermaphroditica syn Callitriche autumnalis- Northern water-starwort, autumnal water-starwort
• Callitriche heterophylla - Twoheaded water-starwort, different-leaved water-starwort
• Callitriche palustris syn Callitriche palustris var. verna, Callitriche verna - Vernal water-starwort, spring water-starwort
• Calochortus apiculatus - Pointedtip mariposa lily
• Calochortus elegans - Elegant mariposa lily, northwest mariposa lily, elegant cat's ear
• Calochortus eurycarpus - White mariposa lily, wide-fruited mariposa, big-pod mariposa lily
• Calochortus longebarbatus - long-bearded mariposa lily, long-bearded sego lily
• Calochortus lyallii - Lyall's mariposa lily
• Calochortus macrocarpus - Bigpod mariposa, Sagebrush mariposa lily
• Calochortus nitidus - Broadfruit mariposa lily
• Calochortus subalpinus syn Calochortus lobbii - Subalpine mariposa lily
• Calochortus tolmiei syn Calochortus caeruleus var. maweanus, Calochortus elegans var. lobbii, Calochortus maweanus, Calochortus purdyi - Tolmie's mariposa-lily, cat's-ears, Tolmie star-tulip
• Caltha leptosepala - Elkslip, White marsh marigold
• Caltha leptosepala ssp. howellii syn Caltha biflora, Caltha biflora ssp. howellii, Caltha howellii, Caltha leptosepala ssp. biflora, Caltha leptosepala var. biflora - Howell's marsh marigold, Twinflower Marsh Marigold
• Caltha palustris - Cowslip, Yellow marsh marigold
• Calypso bulbosa - Fairy slipper
• Calystegia soldanella Syn Convolvulus soldanella - Beach morning-glory, seashore false bindweed, Shore Morning Glory, sea bindweed
• Camassia leichtlinii - Large camas
• Camassia quamash - Common camass, Small camas, Swamp sego
• Camissonia andina syn Oenothera andina - Blackfoot River evening-primrose, obscure suncup, Blackfoot river suncup
• Camissonia contorta syn Oenothera contorta, Oenothera cruciata, Oenothera dentata - Plains evening-primrose
• Camissonia hilgardii syn Oenothera andina var. hilgardii, Oenothera contorta var. hilgardii, Oenothera hilgardii - Hilgard's suncup
• Camissonia minor syn Oenothera minor, Oenothera minor var. cusickii, Sphaerostigma minor - small evening-primrose, Green River suncup
• Camissonia pygmaea syn Oenothera boothii var. pygmaea, Oenothera pygmaea - dwarf suncup
• Camissonia subacaulis syn Jussiaea subacaulis, Oenothera heterantha, Oenothera subacaulis - Diffuseflower evening-primrose, long-leaf evening-primrose
• Camissonia tanacetifolia - Tansy-leaf Evening-primrose
• Campanula aparinoides syn Campanula aparinoides var. grandiflora, Campanula aparinoides var. uliginosa, Campanula uliginosa - Marsh bellflower
• Campanula lasiocarpa syn Campanula lasiocarpa ssp. latisepala, Campanula latisepala, Campanula latisepala var. dubia - Mountain harebell, Alaska harebell, Alaska bellflower
• Campanula parryi - Parry's bellflower, Parry's harebell
• Campanula persicifolia syn Campanula persicifolia var. alba - peach-leaf bellflower
• Campanula piperi - Olympic bellflower
• Campanula rapunculoides syn Campanula rapunculoides var. ucranica - rampion bellflower, rover harebell, creeping bellflower
• Campanula rotundifolia syn Campanula alaskana, Campanula dubia, Campanula gieseckiana, Campanula gieseckiana ssp. groenlandica, Campanula gieseckiana var. arctica, Campanula groenlandica, Campanula heterodoxa, Campanula intercedens, Campanula petiolata, Campanula rotundifolia ssp. groenlandica, Campanula rotundifolia ssp. intercedens, Campanula rotundifolia var. alaskana, Campanula rotundifolia var. alpina, Campanula rotundifolia var. arctica, Campanula rotundifolia var. intercedens, Campanula rotundifolia var. lancifolia, Campanula rotundifolia var. petiolata, Campanula rotundifolia var. velutina, Campanula sacajaweana - Bluebell bellflower, Bluebell-of-Scotland, Harebell
• Campanula scabrella - rough bellflower, rough harebell
• Campanula scouleri - Bellflower, Harebell, Pale bellflower
• Canadanthus modestus syn Aster major, Aster modestus, Aster unalaschkensis var. major, Weberaster modestus - Giant mountain aster, few flowered aster, great northern aster
• Cardamine angulata - seaside bittercress, angled bittercress
• Cardamine bellidifolia - Alpine bittercress
• Cardamine cordifolia - Heartleaf bittercress, Lyall's bittercress, large mountain bittercress
• Cardamine nuttallii - Nuttall's toothwort, slender toothwort
• Cardamine oligosperma Syn Cardamine umbellata - Little Western bittercress, Few-Seeded Bitter-Cress, little Bittercress, Bitter-cress, Toothwort, Idaho Bittercress
• Cardamine pensylvanica syn Cardamine pensylvanica var. brittoniana - Pennsylvania bittercress
• Cardionema ramosissimum syn Cardionema ramosissima, Loeflingia ramosissima - sandcarpet
• Carex albonigra - black-and-white-scaled sedge
• Carex aquatilis - Leafy tussock sedge, Water sedge
• Carex amplifolia - big-leaf sedge
• Carex angustata syn Carex egregia, Carex eurycarpa, Carex eurycarpa var. attenuata?, Carex oxycarpa, Carex striata var. erecta - wide-fruited sedge, many-fruit sedge
• Carex anthoxanthea - grassy-slope arctic sedge, yellow-flowered sedge
• Carex aquatilis - Water sedge
• Carex arcta - northern clustered sedge
• Carex atherodes - wheat sedge, awned sedge
• Carex athrostachya - slender-beak sedge
• Carex atrosquama syn Carex apoda, Carex atrata ssp. atrosquama, Carex atrata var. atrosquama - Lesser blackscale sedge, blackened sedge
• Carex aurea - Golden sedge, pumpkin sedge
• Carex backii syn Carex backii var. subrostrata, Carex durifolia, Carex durifolia var. subrostrata - Back's sedge, Rocky Mountain sedge
• Carex bebbii - Bebb's sedge
• Carex breweri syn Carex breweri var. breweri - Brewer's sedge
• Carex brunnescens - Brownish sedge
• Carex buxbaumii - Buxbaum's sedge, brown bog sedge
• Carex canescens - Silvery sedge, grey sedge
• Carex capillaris syn Carex boecheriana, Carex capillaris ssp. chlorostachys, Carex capillaris ssp. robustior, Carex capillaris var. elongata, Carex capillaris var. fuscidula, Carex capillaris var. major - Hairlike sedge, hair sedge
• Carex capitata syn Carex capitata L. ssp. capitata - capitate sedge
• Carex chordorrhiza - Creeping sedge, cordroot sedge, rope-root sedge
• Carex comosa - Longhair sedge, bristly sedge, bearded sedge
• Carex crawei - Crawe's sedge
• Carex crawfordii syn Carex crawfordii var. vigens- Crawford's sedge
• Carex deflexa - Northern sedge
• Carex deweyana - Dewey sedge
• Carex diandra - Lesser panicled sedge, lesser tussock sedge
• Carex disperma - Softleaf sedge, short-leaf sedge
• Carex douglasii - Douglas' sedge
• Carex duriuscula syn Carex eleocharis, Carex stenophylla, Carex stenophylla ssp. eleocharis, Carex stenophylla var. enervis - Needleleaf sedge, narrow-leaved sedge
• Carex echinata - Star sedge, prickly sedge, stellate sedge
• Carex feta syn Carex straminea var. mixta - green-sheath sedge
• Carex filifolia syn Carex elyniformis, Carex filifolia var. filifolia - Threadleaf Sedge
• Carex flava syn Carex flava var. fertilis, Carex flava var. gaspensis, Carex flava var. graminis, Carex flava var. laxior, Carex flava var. rectirostra, Carex nevadensis ssp. flavella - Yellow sedge, yellow-green sedge
• Carex fracta - fragile-sheath sedge
• Carex garberi syn Carex garberi ssp. bifaria, Carex garberi var. bifaria - Elk sedge, Garber's sedge
• Carex geyeri - Geyer's sedge, Elk Sedge
• Carex gynocrates syn Carex dioica, Carex dioica ssp. gynocrates, Carex dioica var. gynocrates, Carex parallela - Northern bog sedge, yellow bog sedge
• Carex hendersonii - Henderson Sedge
• Carex heteroneura - Different-nerve sedge
• Carex hoodii - Hood's sedge
• Carex hystericina syn Carex hystricina - Bottlebrush sedge, porcupine sedge
• Carex illota - sheep sedge, small-head sedge
• Carex inops - Long-stoloned sedge
• Carex interior syn Carex interior ssp. charlestonensis, Carex interior var. keweenawensis - Inland sedge
• Carex interrupta syn Carex interrupta var. distenta - green-fruited sedge
• Carex jonesii - Jones' sedge
• Carex lachenalii syn Carex bipartita, Carex bipartita var. austromontana - Twotipped sedge
• Carex laeviculmis syn Carex deweyana var. sparsiflora - smooth-stemmed sedge
• Carex lasiocarpa syn Carex lasiocarpa ssp. americana - Woollyfruit sedge
• Carex lapponica - Lapland sedge
• Carex lenticularis - lakeshore sedge, few-ribbed sedge
• Carex leptalea syn Carex leptalea ssp. leptalea - Bristlystalked sedge
• Carex limosa - Mud sedge
• Carex livida - Livid sedge, glaucous sedge, pale sedge
• Carex luzulina - woodrush sedge, spring sedge
• Carex lyngbyei syn Carex cryptocarpa, Carex cryptochlaena, Carex lyngbyei var. robusta - Lyngbye's sedge
• Carex macrocephala - Big-head sedge, Largehead sedge
• Carex macrochaeta - Large-awn sedge
• Carex magellanica - Boreal bog sedge, poor sedge
• Carex mertensii - Mertens' sedge
• Carex microptera syn Carex festivella, Carex limnophila, Carex macloviana ssp. festivella, Carex macloviana var. microptera, Carex microptera var. crassinervia, Carex microptera var. limnophila - Smallwing sedge
• Carex nardina syn Carex nardina ssp. hepburnii, Carex nardina var. hepburnii - spikenard sedge, Spike sedge
• Carex nebrascensis - Nebraska sedge
• Carex nigricans - Black alpine sedge
• Carex norvegica - Norway sedge, Scandinavian sedge
• Carex nudata syn Carex hallii, Carex suborbiculata - naked sedge, torrent sedge
• Carex obnupta syn Carex magnifica - Slough sedge
• Carex obtusata - Obtuse sedge, blunt sedge
• Carex pachystachya syn Carex festiva var. gracilis, Carex festiva var. pachystachya, Carex macloviana ssp. pachystachya, Carex macloviana var. pachystachya, Carex multimoda, Carex pachystachya var. gracilis, Carex pachystachya var. monds-coulteri, Carex pyrophila - chamisso sedge, thick-head sedge
• Carex pauciflora - Fewflower sedge
• Carex pellita syn Carex lanuginosa, Carex lasiocarpa var. latifolia - Woolly sedge
• Carex petasata - Liddon's sedge
• Carex pluriflora syn Carex rariflora var. pluriflora, Carex stygia - many-flower sedge, several-flower sedge
• Carex praeceptorium - early sedge, teacher's sedge
• Carex praegracilis syn Carex camporum - clustered field sedge
• Carex praticola syn Carex praticola var. subcoriacea - Meadow sedge, northern meadow sedge
• Carex proposita - Great Smoky Mountain sedge
• Carex pyrenaica - Pyrenean sedge
• Carex raynoldsi syn Carex lyallii - Raynolds' sedge
• Carex retrorsa - Knotsheath sedge, retrorse sedge
• Carex rossii syn Carex brevipes, Carex deflexa var. rossii, Carex diversistylis - Ross' sedge
• Carex rostrata syn Carex rostrata var. ambigens - Beaked sedge, Swollen beaked sedge
• Carex saxatilis syn Carex ambusta, Carex miliaris, Carex physocarpa, Carex ×physocarpioides, Carex rhomalea, Carex rotundata var. compacta, Carex saxatilis ssp. laxa, Carex saxatilis var. major, Carex saxatilis var. miliaris, Carex saxatilis var. rhomalea - Rock sedge
• Carex scirpoidea - Northern singlespike sedge, western single-spiked sedge
• Carex scoparia - Broom sedge
• Carex scopulorum - mountain sedge, Sierra alpine sedge
• Carex siccata syn Carex aenea, Carex foenea, Carex foenea var. enervis, Carex foenea var. foenea, Carex foenea var. tuberculata - Dryspike sedge, bronze sedge, hay sedge, Fernald's hay sedge, hillside sedge, dry land sedge
• Carex simulata - analogue sedge
• Carex spectabilis syn Carex invisa, Carex nigella - showy sedge
• Carex stipata - Awl-fruited sedge, Owlfruit sedge, Stalk-grain sedge, sawbeak sedge
• Carex stylosa syn Carex stylosa var. nigritella - variegated sedge, long-style sedge
• Carex sychnocephala - many-headed sedge
• Carex tenera syn Carex tenera var. echinodes - Quill sedge, slender sedge
• Carex tenuiflora - Sparseflower sedge, sparse-leaved sedge
• Carex tumulicola - Foothill sedge, splitawn sedge, Berkeley Sedge
• Carex unilateralis - lateral sedge, one-sided sedge
• Carex utriculata syn Carex inflata var. utriculata, Carex rhynchophysa, Carex rostrata var. utriculata - Northwest Territory sedge, inflated sedge, beaked sedge
• Carex vernacula syn Carex foetida, Carex foetida var. vernacula - Native sedge
• Carex vesicaria syn Carex inflata, Carex vesicaria var. vesicaria - Blister sedge, small inflated sedge
• Carex viridula syn Carex viridula var. viridula - Little green sedge, green sedge
• Carex vulpinoidea syn Carex vulpinoidea var. vulpinoidea - Fox sedge
• Cassiope lycopodioides - clubmoss mountain heather, ground pine heather
• Cassiope mertensiana - Western moss heather, Mertens' mountain heather
• Cassiope tetragona - four-angled mountain heather, white arctic mountain heather
• Castilleja ambigua - paint-brush owl-clover, johnny-nip
• Castilleja affinis - Coast Indian paintbrush, Tiburon paintbrush, Tiburon Indian paintbrush
• Castilleja attenuata syn Orthocarpus attenuatus - Narrow-leaved owl-clover, attenuate Indian paintbrush, valley-tassels
• Castilleja cervina - deer Indian paintbrush
• Castilleja cryptantha - obscure Indian paintbrush
• Castilleja cusickii syn Castilleja lutea - Cusick's Indian paintbrush
• Castilleja elmeri syn Castilleja angustifolia var. whitedii - Wenatchee Indian paintbrush, Elmer's paintbrush
• Castilleja hispida - Harsh Indian paintbrush
• Castilleja levisecta - Golden Indian paintbrush
• Castilleja lutescens - Stiff yellow Indian paintbrush, , yellow paintbrush
• Castilleja miniata - Giant red Indian paintbrush, Meadow paintbrush, scarlet Indian paintbrush
• Castilleja minor - lesser Indian paintbrush
• Castilleja parviflora - Mountain Indian paintbrush, Rosy Indian paintbrush, Small-flower indian-paintbrush
• Castilleja rhexiifolia syn Castilleja lauta, Castilleja leonardii, Castilleja oregonensis - Rosy indian-paintbrush, Splitleaf Indian paintbrush
• Castilleja rupicola - Cliff Indian paintbrush
• Castilleja suksdorfii - Suksdorf's Indian paintbrush
• Castilleja sulphurea syn Castilleja luteovirens, Castilleja mogollonica, Castilleja rhexiifolia var. sulphurea - Sulphur Indian paintbrush, Sulphur Paintbrush
• Castilleja tenuis syn Orthocarpus hispidus - hairy Indian paintbrush, thin paintbrush
• Castilleja thompsonii syn Castilleja villicaulis - Thompson's Indian Paintbrush
• Ceanothus integerrimus syn Ceanothus andersonii, Ceanothus californicus, Ceanothus integerrimus var. californicus, Ceanothus integerrimus var. macrothyrsus, Ceanothus integerrimus var. puberulus - Deerbrush
• Ceanothus prostratus syn Ceanothus divergens ssp. occidentalis, Ceanothus prostratus var. laxus, Ceanothus prostratus var. occidentalis - prostrate ceanothus, mahala mat, squawcarpet
• Ceanothus sanguineus syn Ceanothus oreganus - Oregon Teatree, Redstem ceanothus, Wild lilac
• Ceanothus velutinus - Buckbush, Mountain balm, Snowbrush ceanothus, Tobacco-brush
• Celtis laevigata - Hackberry, Netleaf Hackberry, Palo blanco, Sugar hackberry, Sugarberry, Western Hackberry
• Cenchrus longispinus syn Cenchrus carolinianus - mat sandbur, innocent-weed
• Centaurium exaltatum syn Centaurium namophilum var. nevadense, Centaurium nuttallii, Cicendia exaltata - desert centaury, western centaury, Great Basin centaury
• Cephalanthera austiniae - phantom orchid
• Cerastium arvense Syn Cerastium alsophilum, Cerastium angustatum, Cerastium arvense f. oblongifolium, Cerastium arvense subsp. strictum, Cerastium arvense var. angustifolium, Cerastium arvense var. arvense, Cerastium arvense var. latifolium, Cerastium arvense var. purpurascen, arvense var. villosum, Cerastium arvense var. viscidulum, Cerastium campestre, Cerastium confertum, Cerastium effusum, Cerastium elongatum, Cerastium latifolium, Cerastium nitidum, Cerastium oblongifolium, Cerastium occidentale, Cerastium oreophilum, Cerastium patulum, Cerastium scopulorum, Cerastium sonnei, Cerastium strictum, Cerastium subulatum, Cerastium tenuifolium, Cerastium vestitum, Cerastium villosum - Field chickweed, starry grasswort, field mouse-ear, field mouse-ear chickweed, meadow chickweed, prairie mouse-ear chickweed, starry grasswort, céraiste des champs
• Cerastium beeringianum syn Cerastium berringianum - Bering chickweed
• Cerastium brachypodum syn Cerastium brachypodum var. compactum, Cerastium nutans var. brachypodum - Shortstalk chickweed
• Cerastium nutans - - Nodding chickweed
• Ceratophyllum demersum syn Ceratophyllum apiculatum, Ceratophyllum demersum var. apiculatum - Coon's tail
• Ceratophyllum echinatum syn Ceratophyllum demersum . var. echinatum, Ceratophyllum submersum var. echinatum - Spineless hornwort, prickly hornwort, spiny coontail
• Cercocarpus ledifolius - Curl-leaf mountain-mahogany
• Chaenactis douglasii - Douglas' dustymaiden, Dusty Maiden, hoary false yarrow
• Chaenactis thompsonii - Thompson's pincushion
• Chamaecyparis nootkatensis syn Cupressus nootkatensis - Alaska yellow cedar, Nootka Cedar or cypress, Sitka cedar or cypress
• Chamaesyce glyptosperma syn Euphorbia glyptosperma - rib-seed sandmat, corrugate seeded spurge, ridge seeded spurge
• Chamaesyce serpyllifolia - thyme-leaved spurge
• Chamerion angustifolium - Fireweed
• Chamerion latifolium syn Chamaenerion latifolium, Chamerion subdentatum, Epilobium latifolium - Broad-leaf fireweed, Dwarf fireweed
• Cheilanthes gracillima syn Cheilanthes gracillima var. aberrans - Lace lip fern
• Chenopodium berlandieri - Pitseed goosefoot
• Chenopodium capitatum syn Blitum capitatum - Blite goosefoot, strawberry-blite
• Chenopodium leptophyllum syn Chenopodium album var. leptophyllum - Narrowleaf goosefoot, slender goosefoot, slimleaf lambsquarters
• Chenopodium rubrum - Red goosefoot, coast-blite goosefoot, red pigweed
• Chenopodium simplex syn Chenopodium gigantospermum, Chenopodium hybridum, Chenopodium hybridum ssp. gigantospermum, Chenopodium hybridum var. gigantospermum, Chenopodium hybridum var. simplex - Mapleleaf goosefoot, giantseed goosefoot
• Chenopodium subglabrum syn Chenopodium leptophyllum var. subglabrum - Smooth goosefoot
• Chimaphila menziesii - Little Pipsissewa, Little prince's pine
• Chimaphila umbellata - Pipsissewa, common prince's-pine
• Chrysolepis chrysophylla - Giant chinquapin, Golden Chinkapin
• Chrysosplenium glechomifolium syn Chrysosplenium glechomaefolium - Pacific golden-saxifrage, Pacific watercarpet
• Chrysosplenium tetrandrum syn Chrysosplenium alternifolium ssp. tetrandrum, Chrysosplenium alternifolium var. tetrandrum - Northern golden saxifrage
• Chrysothamnus viscidiflorus - yellow rabbitbrush, lanceleaf green rabbitbrush, green rabbitbrush
• Cicuta bulbifera - Bulblet-bearing water hemlock
• Cicuta douglasii - Water-hemlock, western water-hemlock, Douglas' water-hemlock
• Cicuta maculata - Beaver Poison, Spotted water hemlock, Water-Hemlock, spotted cowbane
• Cinna latifolia - drooping woodreed, slender woodreed
• Circaea alpina - Small enchanter's nightshade
• Cirsium brevifolium syn Cirsium palousense - Palouse thistle
• Cirsium brevistylum - clustered thistle, Short-Styled Thistle, Indian thistle
• Cirsium edule syn Carduus macounii, Cirsium hallii, Cirsium macounii - Edible thistle
• Cirsium foliosum syn Cirsium foliosum var. minganense - Elk thistle
• Cirsium hookerianum - white thistle, Hooker's thistle
• Cirsium scariosum syn Carduus americanus, Carduus coloradensis, Cirsium acaule var. americanum, Cirsium acaulescens, Cirsium americanum, Cirsium butleri, Cirsium coloradense, Cirsium coloradense ssp. acaulescens, Cirsium coloradense ssp. longissimum, Cirsium congdonii, Cirsium drummondii ssp. lanatum, Cirsium drummondii ssp. latisquamum, Cirsium drummondii ssp. vexans, Cirsium drummondii var. acaulescens, Cirsium drummondii var. oregonense, Cirsium erosum, Cirsium kelseyi, Cirsium lacerum, Cirsium magnificum, Cirsium minganense, Cirsium oreophilum, Cirsium quercetorum var. citrinum, Cirsium scariosum var. thorneae, Cirsium tioganum, Cirsium tioganum var. coloradense, Cnicus drummondii var. acaulescens, Cnicus tioganus - Meadow thistle
• Cirsium undulatum - Plumed Thistle, Wavyleaf thistle
• Cistanthe tweedyi syn Calandrinia tweedyi, Lewisia tweedyi - Tweedy's pussypaws, Tweedy's lewisia
• Cistanthe umbellata - Mt. Hood pussypaws
• Clarkia amoena - Farewell-to-spring, Herald-of-summer
• Clarkia gracilis - slender clarkia
• Clarkia pulchella - Deerhorn, Clarkia Pinkfairies
• Clarkia purpurea - Winecup clarkia
• Clarkia rhomboidea - Common Clarkia, Diamond clarkia, diamond fairyfan
• Claytonia arenicola syn Montia arenicola - sand springbeauty
• Claytonia cordifolia syn Claytonia sibirica L. var. cordifolia, Montia cordifolia - Broadleaf Claytonia, Heartleaf springbeauty
• Claytonia exigua syn Montia spathulata - serpentine springbeauty, Pale Spring Beauty
• Claytonia lanceolata - Lanceleaf springbeauty
• Claytonia m