Names beginning with O: oak, oak-fern, oatgrass, oats, ocean-spray, oenanthe, oenothera, old man in the spring, old-man, old-man's beard, old-man's-beard, old-woman, olive, Omphalina, onion, oniongrass, ookow, orache, orange wall lichen, orange-peel, orchid, Oregon-grape, Oregon-tea, oreocarya, Osage-orange, osier, oso-berry, ovalpurse, owl-clover, ox-tongue, oxtongue, oyster, oysterette, oysterling
Oak
British oak (Quercus robur) – 8 photos
English oak (Quercus robur) – 8 photos
Jerusalem oak (Dysphania botrys) – 28 photos
Oregon white oak (Quercus garryana) – 32 photos
Oregon white oak (Quercus garryana var. garryana) – 30 photos
Oak-fern
Pacific oak-fern (Gymnocarpium disjunctum) – 27 photos
western oak-fern (Gymnocarpium disjunctum) – 27 photos
Oatgrass
bulbous oatgrass (Arrhenatherum elatius) – 42 photos
California oatgrass (Danthonia californica) – 22 photos
few-flower oatgrass (Danthonia unispicata) – 16 photos
one-spike oatgrass (Danthonia unispicata) – 16 photos
poverty oatgrass (Danthonia spicata) – 10 photos
timber oatgrass (Danthonia intermedia) – 4 photos
Oats
barbed oats (Avena barbata) – 12 photos
cultivated oats (Avena sativa) – 8 photos
Ocean-spray
creambush ocean-spray (Holodiscus discolor) – 84 photos
hillside ocean-spray (Holodiscus discolor) – 84 photos
ocean-spray (Holodiscus discolor) – 84 photos
Oenanthe
Oenothera
Old man in the spring
old man in the spring (Senecio vulgaris) – 32 photos
Old-man
Old-man's beard
old-man's beard (Clematis vitalba) – 33 photos
Old-man's-beard
old-man's-beard (Hericium erinaceus) – 2 photos
Old-woman
Olive
autumn olive (Elaeagnus umbellata) – 18 photos
Omphalina
Wynne's Omphalina (Chrysomphalina grossula) – 6 photos
Onion
Blue Mountain onion (Allium dictuon) – 1 photo
Columbia onion (Allium columbianum) – 13 photos
Cuddy Mountain onion (Allium fibrillum) – 38 photos
Douglas' onion (Allium douglasii) – 25 photos
fragile onion (Allium scilloides) – 52 photos
fringed onion (Allium fibrillum) – 38 photos
Geyer's onion (Allium geyeri) – 4 photos
Geyer's onion (Allium geyeri var. geyeri) – 14 photos
Grand Coulee onion (Allium constrictum) – 17 photos
narrow-leaf onion (Allium amplectens) – 17 photos
Nevius's onion (Allium nevii) – 62 photos
nodding onion (Allium cernuum) – 35 photos
Pacific onion (Allium validum) – 20 photos
Robinson's onion (Allium robinsonii) – 68 photos
rock onion (Allium macrum) – 38 photos
rosy Sierra onion (Allium campanulatum) – 7 photos
Rydberg's onion (Allium geyeri var. tenerum) – 9 photos
scalloped onion (Allium crenulatum) – 54 photos
scilla-like onion (Allium scilloides) – 52 photos
swamp onion (Allium validum) – 20 photos
taper-tip onion (Allium acuminatum) – 132 photos
textile onion (Allium textile) – 4 photos
Tolmie's onion (Allium tolmiei) – 4 photos
Tolmie's onion (Allium tolmiei var. tolmiei) – 31 photos
twinleaf onion (Allium anceps) – 4 photos
two-edged onion (Allium anceps) – 4 photos
white wild onion (Allium textile) – 4 photos
Oniongrass
Alaska oniongrass (Melica subulata) – 22 photos
bulbous oniongrass (Melica bulbosa) – 2 photos
Ookow
Orache
garden orache (Atriplex hortensis) – 5 photos
Gmelin's orache (Atriplex gmelinii) – 23 photos
Gmelin's orache (Atriplex gmelinii var. gmelinii) – 8 photos
halberdleaf orache (Atriplex patula) – 10 photos
hastate orache (Atriplex prostrata) – 32 photos
long-stalked orache (Atriplex longipes) – 2 photos
oblongleaf orache (Atriplex oblongifolia) – 10 photos
red orache (Atriplex rosea) – 16 photos
Russian atriplex orache (Atriplex heterosperma) – 24 photos
silver orache (Atriplex argentea) – 6 photos
silverscale orache (Atriplex argentea) – 6 photos
spear orache (Atriplex patula) – 10 photos
thickleaf orache (Atriplex dioica) – 14 photos
thin-leaf orache (Atriplex prostrata) – 32 photos
tumbling orache (Atriplex rosea) – 16 photos
wedge orache (Atriplex truncata) – 7 photos
wedgeleaf orache (Atriplex truncata) – 7 photos
wedgescale orache (Atriplex truncata) – 7 photos
Orange wall lichen
elegant orange wall lichen (Rusavskia elegans) – 6 photos
Orange-peel
orange-peel (Aleuria aurantia) – 9 photos
Orchid
canyon bog orchid (Platanthera sparsiflora) – 7 photos
canyon bog orchid (Platanthera stricta) – 60 photos
choriso bog orchid (Platanthera chorisiana) – 6 photos
dense orchid (Platanthera elongata) – 34 photos
dense-flower rein orchid (Platanthera elongata) – 34 photos
eagle rein orchid (Platanthera aquilonis) – 5 photos
fen orchid (Liparis loeselii) – 1 photo
frog orchid (Dactylorhiza viridis) – 6 photos
large round-leaf orchid (Platanthera orbiculata) – 42 photos
long-bracted green orchid (Dactylorhiza viridis) – 6 photos
needle-spur green orchid (Platanthera stricta) – 60 photos
phantom orchid (Cephalanthera austiniae) – 35 photos
royal rein orchid (Platanthera transversa) – 48 photos
Sheviak's bog orchid (Platanthera aquilonis) – 5 photos
slender bog orchid (Platanthera stricta) – 60 photos
white orchid (Platanthera dilatata) – 48 photos
Oregon-grape
Cascade Oregon-grape (Mahonia nervosa) – 47 photos
creeping Oregon-grape (Mahonia repens) – 48 photos
dull Oregon-grape (Mahonia nervosa) – 47 photos
holly-leaf Oregon-grape (Mahonia aquifolium) – 83 photos
low Oregon-grape (Mahonia repens) – 48 photos
shining Oregon-grape (Mahonia aquifolium) – 83 photos
tall Oregon-grape (Mahonia aquifolium) – 83 photos
Oregon-tea
Oregon-tea (Clinopodium douglasii) – 22 photos
Oreocarya
cockscomb oreocarya (Oreocarya glomerata) – 33 photos
gray oreocarya (Oreocarya leucophaea) – 20 photos
Snake River oreocarya (Oreocarya spiculifera) – 46 photos
Thompson's oreocarya (Oreocarya thompsonii) – 28 photos
Osage-orange
Osage-orange (Maclura pomifera) – 6 photos
Osier
purple osier (Salix purpurea) – 2 photos
western red osier (Cornus occidentalis) – 14 photos
Oso-berry
Ovalpurse
Owl-clover
dwarf owl-clover (Triphysaria pusilla) – 16 photos
golden-tongue owl-clover (Orthocarpus luteus) – 16 photos
Grand Coulee owl-clover (Orthocarpus barbatus) – 34 photos
mountain owl-clover (Orthocarpus imbricatus) – 24 photos
narrow-leaved owl-clover (Orthocarpus tenuifolius) – 30 photos
owl-clover (Castilleja) – 1 photo
rosy owl-clover (Orthocarpus bracteosus) – 28 photos
thin-leaved owl-clover (Orthocarpus tenuifolius) – 30 photos
Ox-tongue
hawkweed ox-tongue (Picris hieracioides) – 3 photos
Oxtongue
Oyster
leaflike oyster (Hohenbuehelia petaloides) – 2 photos
oak oyster (Pleurotus dryinus) – 7 photos
shoehorn oyster (Hohenbuehelia petaloides) – 2 photos
small moss oysterling (Arrhenia retiruga) – 1 photo
smelly oyster (Phyllotopsis nidulans) – 7 photos
veiled oyster (Pleurotus dryinus) – 7 photos
Oysterette
white oysterette (Cheimonophyllum candidissimum) – 3 photos
Oysterling
bitter oysterling (Panellus stipticus) – 4 photos
lilac oysterling (Panus conchatus) – 4 photos
peeling oysterling (Crepidotus mollis cf.) – 2 photos
