List of Canadian plants by family O

Main page: List of Canadian plants by family

This is an incomplete list that may never be able to satisfy particular standards for completeness. You can help by expanding it with reliably sourced entries.

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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
Malaxis brachypoda — white adder's-mouth
Malaxis diphyllos — Aleutian adder's-mouth
Malaxis paludosa — bog adder's-mouth
Malaxis unifolia — green adder's-mouth
Neottia auriculata — auricled twayblade
Neottia australis — southern twayblade
Neottia borealis — northern twayblade
Neottia caurina — western twayblade
Neottia convallarioides — broad-leaved twayblade

Neottia cordata — heartleaf twayblade
Neottia x veltmanii — Veltman's twayblade
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 — Bog rein orchid, 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 claytoniana — interrupted fern

Osmunda spectabilis — royal fern
Osmundastrum cinnamomeum — cinnamon 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