List of Canadian plants by family O

Families: A | B | C | D | E | F | G | H | I J K | L | M | N | O | P Q | R | S | T | U V W | X Y Z

Oedipodiaceae

• Oedipodium griffithianum

Oleaceae

• Fraxinus americana — white ash
• Fraxinus latifolia — Oregon ash
• Fraxinus nigra — black ash

• Fraxinus pennsylvanica — green ash
• Fraxinus profunda — pumpkin ash
• Fraxinus quadrangulata — blue ash

Onagraceae

• Boisduvalia densiflora — denseflower spike-primrose
• Boisduvalia glabella — smooth spike-primrose
• Calylophus serrulatus — yellow evening-primrose
• Camissonia andina — Blackfoot River suncup
• Camissonia breviflora — shortflower suncup
• Camissonia contorta — dwarf contorted suncup
• Circaea alpina — small enchanter's-nightshade
• Circaea lutetiana — southern broadleaf enchanter's-nightshade
• Circaea x intermedia — intermediate enchanger's-nightshade
• Clarkia amoena — farewell-to-spring
• Clarkia pulchella — largeflower clarkia
• Clarkia purpurea — winecup clarkia
• Clarkia rhomboidea — tongue clarkia
• Epilobium anagallidifolium — alpine willowherb
• Epilobium angustifolium — fireweed
• Epilobium arcticum — arctic willowherb
• Epilobium brachycarpum — panicled willowherb
• Epilobium ciliatum — hairy willowherb
• Epilobium clavatum — clavate-fruit willowherb
• Epilobium coloratum — purpleleaf willowherb
• Epilobium davuricum — Dahuria willowherb
• Epilobium foliosum — California willowherb
• Epilobium glaberrimum — glaucous willowherb
• Epilobium halleanum — glandular willowherb
• Epilobium hornemannii — Hornemann's willowherb
• Epilobium lactiflorum — whiteflower willowherb
• Epilobium latifolium — river beauty
• Epilobium leptocarpum — slender-fruited willowherb
• Epilobium leptophyllum — linear-leaved willowherb

• Epilobium luteum — yellow willowherb
• Epilobium minutum — smallflower willowherb
• Epilobium mirabile — Olimple Mountain willowherb
• Epilobium oregonense — Oregon willowherb
• Epilobium palustre — marsh willowherb
• Epilobium saximontanum — Rocky Mountain willowherb
• Epilobium strictum — downy willowherb
• Epilobium x wisconsinense
• Gaura biennis — biennial gaura
• Gaura coccinea — scarlet gaura
• Gayophytum diffusum — diffuse groundsmoke
• Gayophytum humile — low groundsmoke
• Gayophytum racemosum — racemed groundsmoke
• Gayophytum ramosissimum — much-branch groundsmoke
• Ludwigia alternifolia — bushy seedbox
• Ludwigia palustris — marsh seedbox
• Ludwigia polycarpa — many-fruit false-loosestrife
• Oenothera biennis — common evening-primrose
• Oenothera caespitosa — tufted evening-primrose
• Oenothera clelandii — lesser four-point evening-primrose
• Oenothera elata — Hooker's evening-primrose
• Oenothera flava — long-tubed evening-primrose
• Oenothera fruticosa — narrowleaf sundrops
• Oenothera nuttallii — white-stemmed evening-primrose
• Oenothera oakesiana — Oakes' evening-primrose
• Oenothera pallida — pale evening-primrose
• Oenothera parviflora — northern evening-primrose
• Oenothera perennis — small sundrops
• Oenothera pilosella — meadow evening-primrose
• Oenothera villosa — hairy evening-primrose

Ophioglossaceae

• Botrychium acuminatum — moonwort
• Botrychium ascendens — upward-lobed moonwort
• Botrychium boreale — northern moonwort
• Botrychium campestre — prairie dunewort
• Botrychium crenulatum — crenulate moonwort
• Botrychium dissectum — cutleaf grapefern
• Botrychium hesperium — western moonwort
• Botrychium lanceolatum — triangle grapefern
• Botrychium lineare — narrowleaf grapefern
• Botrychium lunaria — moonwort grapefern
• Botrychium matricariifolium — chamomile grapefern
• Botrychium minganense — Mingan's moonwort
• Botrychium montanum — mountain moonwort
• Botrychium mormo — little goblin moonwort
• Botrychium multifidum — leathery grapefern

• Botrychium oneidense — bluntlobe grapefern
• Botrychium pallidum — pale moonwort
• Botrychium paradoxum — peculiar moonwort
• Botrychium pedunculosum — stalked moonwort
• Botrychium pinnatum — northern moonwort
• Botrychium pseudopinnatum — false daisyleaf grapefern
• Botrychium rugulosum — rugulose grapefern
• Botrychium simplex — least grapefern
• Botrychium spathulatum — spoonleaf moonwort
• Botrychium tunux
• Botrychium virginianum — rattlesnake fern
• Botrychium x watertonense
• Botrychium yaaxudakeit
• Ophioglossum pusillum — northern adder's-tongue
• Ophioglossum vulgatum — southern adder's-tongue

Orchidaceae

• Amerorchis rotundifolia — round-leaved orchis
• Aplectrum hyemale — puttyroot
• Arethusa bulbosa — dragon's mouth
• Calopogon tuberosus — tuberous grass-pink
• Calypso bulbosa — fairy slipper
• Cephalanthera austiniae — phantom orchid
• Coeloglossum viride — longbract green orchis
• Corallorhiza maculata — spotted coralroot
• Corallorhiza mertensiana — Merten's coralroot
• Corallorhiza odontorhiza — autumn coralroot
• Corallorhiza striata — striped coralroot
• Corallorhiza trifida — early coralroot
• Cypripedium acaule — pink lady's-slipper
• Cypripedium arietinum — ram's-head lady's-slipper
• Cypripedium candidum — small white lady's-slipper
• Cypripedium guttatum — spotted lady's-slipper
• Cypripedium montanum — mountain lady's-slipper
• Cypripedium parviflorum — American yellow lady's-slipper
• Cypripedium passerinum — sparrow's-egg lady's-slipper
• Cypripedium reginae — showy lady's-slipper
• Cypripedium x andrewsii — Andrews' lady's-slipper
• Cypripedium x columbianum — Columbian lady's-slipper
• Cypripedium x favillianum
• Cypripedium x landonii — Landon's lady's-slipper
• Dactylorhiza praetermissa — southern marsh orchid
• Epipactis gigantea — giant helleborine
• Galearis spectabilis — showy orchis
• Goodyera oblongifolia — giant rattlesnake-plantain
• Goodyera pubescens — downy rattlesnake-plantain
• Goodyera repens — dwarf rattlesnake-plantain
• Goodyera tesselata — checkered rattlesnake-plantain
• Isotria medeoloides — small whorled pogonia
• Isotria verticillata — large whorled pogonia
• Liparis liliifolia — large twayblade
• Liparis loeselii — Lösel's twayblade
• Listera auriculata — auricled twayblade
• Listera australis — southern twayblade
• Listera borealis — northern twayblade
• Listera caurina — western twayblade
• Listera convallarioides — broad-leaved twayblade
• Listera cordata — heartleaf twayblade
• Listera x veltmanii — Veltman's twayblade
• Malaxis brachypoda — white adder's-mouth
• Malaxis diphyllos — Aleutian adder's-mouth
• Malaxis paludosa — bog adder's-mouth

• Malaxis unifolia — green adder's-mouth
• Piperia candida — white piperia
• Piperia elegans — hillside rein orchid
• Piperia elongata — denseflower rein orchid
• Piperia transversa — royal rein orchid
• Piperia unalascensis — Alaska rein orchid
• Platanthera albida — vanilla-scent bog orchid
• Platanthera aquilonis
• Platanthera blephariglottis — white-fringe orchis
• Platanthera chorisiana — Choriso bog orchid
• Platanthera clavellata — small green woodland orchid
• Platanthera dilatata — leafy white orchis
• Platanthera flava — southern rein orchid
• Platanthera grandiflora — large purple-fringe orchis
• Platanthera hookeri — Hooker's orchis
• Platanthera hyperborea — leafy northern green orchid
• Platanthera lacera — green-fringe orchis
• Platanthera leucophaea — eastern prairie white-fringed orchid
• Platanthera leucostachys — scentbottle
• Platanthera obtusata — small northern bog orchid
• Platanthera orbiculata — large roundleaf orchid
• Platanthera praeclara — western prairie white-fringed orchid
• Platanthera psycodes — small purple-fringe orchis
• Platanthera stricta — slender bog orchid
• Platanthera x andrewsii — Andrews' platanthera
• Platanthera x hollandiae — Holland's platanthera
• Platanthera x keenanii — Keenan's platanthera
• Platanthera x media
• Platanthera x reznicekii — Reznicek's platanthera
• Platanthera x vossii — Voss' platanthera
• Pogonia ophioglossoides — rose pogonia
• Spiranthes casei — Case's ladies'-tresses
• Spiranthes cernua — nodding ladies'-tresses
• Spiranthes lacera — southern slender ladies'-tresses
• Spiranthes lucida — shining ladies'-tresses
• Spiranthes magnicamporum — Great Plains ladies'-tresses
• Spiranthes ochroleuca — yellow nodding ladies'-tresses
• Spiranthes ovalis — lesser ladies'-tresses
• Spiranthes romanzoffiana — hooded ladies'-tresses
• Spiranthes x intermedia
• Spiranthes x simpsonii — Simpson's ladies'-tresses
• Triphora trianthophora — nodding pogonia

Orobanchaceae

• Boschniakia hookeri — Vancouver groundcone
• Boschniakia rossica — northern groundcone
• Boschniakia strobilacea — California groundcone
• Conopholis americana — American cancer-root
• Epifagus virginiana — beechdrops
• Orobanche californica — California broomrape

• Orobanche corymbosa — flat-top broomrape
• Orobanche fasciculata — clustered broomrape
• Orobanche ludoviciana — Louisiana broomrape
• Orobanche pinorum — pine broomrape
• Orobanche uniflora — one-flowered broomrape

Orthotrichaceae

• Amphidium californicum
• Amphidium lapponicum
• Amphidium mougeotii
• Drummondia prorepens
• Orthotrichum affine
• Orthotrichum alpestre
• Orthotrichum anomalum
• Orthotrichum consimile
• Orthotrichum cupulatum
• Orthotrichum gymnostomum
• Orthotrichum hallii
• Orthotrichum laevigatum
• Orthotrichum lyellii
• Orthotrichum obtusifolium — blunt bristle-moss
• Orthotrichum ohioense
• Orthotrichum pallens
• Orthotrichum pellucidum
• Orthotrichum pulchellum
• Orthotrichum pumilum
• Orthotrichum pusillum
• Orthotrichum pylaisii

• Orthotrichum rivulare
• Orthotrichum rupestre
• Orthotrichum sordidum
• Orthotrichum speciosum
• Orthotrichum stellatum
• Orthotrichum stramineum
• Orthotrichum strangulatum
• Orthotrichum striatum
• Orthotrichum tenellum
• Ulota coarctata
• Ulota crispa
• Ulota curvifolia
• Ulota drummondii
• Ulota hutchinsiae
• Ulota megalospora
• Ulota obtusiuscula
• Ulota phyllantha
• Zygodon conoideus
• Zygodon gracilis
• Zygodon reinwardtii
• Zygodon viridissimus

Osmundaceae

• Osmunda cinnamomea — cinnamon fern
• Osmunda claytoniana — interrupted fern

• Osmunda regalis — royal fern

Oxalidaceae

• Oxalis dillenii — Dillen's woodsorrel
• Oxalis montana — white woodsorrel
• Oxalis oregana — Oregon woodsorrel

• Oxalis stricta — common yellow woodsorrel
• Oxalis suksdorfii — western yellow oxalis