Vascular Plants
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Common names beginning with O:
British oak (Quercus robur)
Origin: Introduced from Europe/Africa
English oak (Quercus robur)
Origin: Introduced from Europe/Africa
Jerusalem oak (Dysphania botrys)
Distribution: Occurring chiefly east of the Cascades crest in Washington; widely distributed throughout much of North America.
Habitat: Weed of roadsides, waste areas and streambanks.
Origin: Introduced from Eurasia
Red oak (Quercus rubra)
Origin: Introduced from central and eastern NA
Barbed oat (Avena barbata)
Distribution: Introduced and common in southwest United States; occasional in Washington and western Oregon.
Habitat: Roadsides and waste land.
Origin: Introduced
Beardless false oat (Trisetum wolfii)
Origin: Native
Narrow false oat (Trisetum spicatum)
Distribution: Alaska across Canada to Greenland, south through most of the mountains of western United States and the Appalachians.
Habitat: Montane forests to alpine slopes in rocky, dry or moist areas.
Origin: Native
Oat (Avena sativa)
Distribution: Commonly cultivated throught the United States and Canada, occasionally escaping but usually not persisting.
Habitat: Roadsides and field margins.
Origin: Introduced
Tall false oat (Trisetum canescens)
Origin: Native
Wild oat (Avena fatua)
Distribution: Common introduction in most of western North America.
Habitat: A weed in grain fields, roadsides and waste ground.
Origin: Introduced
Yellow false oat (Trisetum flavescens)
Origin: Introduced
California oatgrass (Danthonia californica)
Distribution: British Columbia south on both sides of the Cascades to California, east to Montana and New Mexico.
Habitat: Open, grassy meadows to rocky ridges, from coastal prairies to mid-elevations in the mountains, often with ponderosa pine.
Origin: Native
Few-flower oatgrass (Danthonia unispicata)
Distribution: British Columbia south on both sides of the Cascades to California, east to Alberta and Colorado.
Habitat: Dry to occasionally moist prairies, foothills, and open parks and ridges in mountain forests.
Origin: Native
One-spike oatgrass (Danthonia unispicata)
Distribution: British Columbia south on both sides of the Cascades to California, east to Alberta and Colorado.
Habitat: Dry to occasionally moist prairies, foothills, and open parks and ridges in mountain forests.
Origin: Native
Poverty oatgrass (Danthonia spicata)
Distribution: Occurring chiefly west of the Cascades crest in Washington; British Columbia south on both sides of the Cascades to Oregon, east to Newfoundland and eastern United States.
Habitat: Sandy to rocky soil in dry woods and fairly dry meadows.
Origin: Native
Timber oatgrass (Danthonia intermedia)
Origin: Native
Creambush ocean-spray (Holodiscus discolor)
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia to south California, east to the Rocky Mountains.
Habitat: Gravelly soil in open, dry to moist woods, coastal bluffs to moderate elevations in the mountains.
Origin: Native
Hillside oceanspray (Holodiscus discolor)
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia to south California, east to the Rocky Mountains.
Habitat: Gravelly soil in open, dry to moist woods, coastal bluffs to moderate elevations in the mountains.
Origin: Native
Oldman (Artemisia absinthium)
Distribution: Introduced in the northern half of the United States and southern Canada
Habitat: Weed of roadsides and waste places
Origin: Introduced
Oldwoman (Artemisia stelleriana)
Distribution: Known from a few locations along the north coast in Washington; known only from Washington in western North America; central Canada and U.S. to the Atlantic Coast.
Habitat: Coastal dunes and beaches.
Origin: Introduced
Blue Mountain onion (Allium dictuon)
Distribution: Blue Mountains of southeast Washington.
Habitat: Open, fairly dry, rocky areas.
Origin: Native
Columbia onion (Allium columbianum)
Distribution: Washington east to western Idaho and in western Montana.
Habitat: Shallow soils on rock outcrops and wet meadows.
Origin: Native
Cuddy Mountain onion (Allium fibrillum)
Distribution: Occurring chiefly in the southeastern counties of Washington; Washington east to Montana, south to Oregon.
Habitat: Moist, shallow soils in the mountains.
Origin: Native
Cultivated onion (Allium cepa)
Origin: Introduced from Old World, exact origin unknown
Douglas' onion (Allium douglasii)
Distribution: East of the Cascades in Washington; central and eastern Washington south to northeastern Oregon.
Habitat: Open, vernally-moist areas at low to moderate elevations.
Origin: Native
Fragile onion (Allium scilloides)
Distribution: Douglas County to Klickitat County, Washington, lower foothills of the Cascades to east of the Columbia River
Habitat: Scablands and dry, barren, gravelly soils.
Origin: Native
Fringed onion (Allium fibrillum)
Distribution: Occurring chiefly in the southeastern counties of Washington; Washington east to Montana, south to Oregon.
Habitat: Moist, shallow soils in the mountains.
Origin: Native
Grand Coulee onion (Allium constrictum)
Distribution: Grant and Douglas Counties, Washington.
Habitat: Shallow, vernally-moist soils in low, open areas.
Origin: Native
Narrow-leaf onion (Allium amplectens)
Distribution: Scattered locations on both sides of the Cascades crest in Washington; British Columbia south to California.
Habitat: Dry slopes and open meadows at low to moderate elevations.
Origin: Native
Nevius's onion (Allium nevii)
Distribution: East slope and foothills of the Cascades, Kittitas County, Washington, south to Wasco County, Oregon
Habitat: Open areas where the soil is wet into the spring
Origin: Native
Nodding onion (Allium cernuum)
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia south to Oregon, east to the Rocky Mountains; also in central and southeastern U.S.
Habitat: Open, somewhat moist areas, sea level to high elevations in the mountains.
Origin: Native
Olympic onion (Allium crenulatum)
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia south to Oregon.
Habitat: Forest openings and mountain meadows, moderate to high elevations.
Origin: Native
Pacific onion (Allium validum)
Origin: Native
Robinson's onion (Allium robinsonii)
Distribution: Near the Columbia River in Washington; Washington south to north-central Oregon.
Habitat: Sand and gravel near the river to rocky, even lithosol benches.
Origin: Native
Rock onion (Allium macrum)
Distribution: In Washington, Kittitas and Douglas Counties south to Walla Walla and Klickitat Counties; more common in north-central Oregon.
Habitat: Lithosol and barren, gravelly soils in the shrub-steppe.
Origin: Native
Rosy Sierra onion (Allium campanulatum)
Distribution: In the mountains in eastern Oregon, California dnd Nevada, and on Bethel Ridge, Yakima County, Washington.
Habitat: Dry soils at medium to high elevations.
Origin: Native
Scalloped onion (Allium crenulatum)
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia south to Oregon.
Habitat: Forest openings and mountain meadows, moderate to high elevations.
Origin: Native
Scilla-like onion (Allium scilloides)
Distribution: Douglas County to Klickitat County, Washington, lower foothills of the Cascades to east of the Columbia River
Habitat: Scablands and dry, barren, gravelly soils.
Origin: Native
Swamp onion (Allium validum)
Origin: Native
Taper-tip onion (Allium acuminatum)
Distribution: British Columbia south to California, east to Wyoming.
Habitat: Common in dry, open, often rocky areas, low to moderate elevations in the mountains.
Origin: Native
Textile onion (Allium textile)
Origin: Native
White wild onion (Allium textile)
Origin: Native
Alaska oniongrass (Melica subulata)
Distribution: Southern Alaska south to California, east to Montana and Wyoming.
Habitat: Open slopes to thick, dry or moist woods, from near sea level to mid-elevations in the mountains.
Origin: Native
Ookow (Dichelostemma congestum)
Distribution: Scattered locations in Washington from the east side of the Olympic Peninsula and Island County to the Columbia River; Washington south to California.
Habitat: Grassy meadows, rocky prairies and sagebrush slopes.
Origin: Native
Bare-stemmed goosefoot; nude orach (Atriplex longipes)
Origin: Introduced
Orach (Atriplex heterosperma)
Distribution: Primarily east of the Cascades crest in Washington; occurring in scattered locations throughout North America.
Habitat: Riparian zones and adjacent fields; tolerant of alkaline.
Origin: Introduced from Eurasia
Red orach (Atriplex rosea)
Distribution: Occurring east of the Cascades crest in Washington; British Columbia south to California, east to the Rocky Mountains; scattered locations in central and eastern U.S.
Habitat: Weedy species of irrigated land and roadsides.
Origin: Introduced from Eurasia
Russian atriplex orach (Atriplex heterosperma)
Distribution: Primarily east of the Cascades crest in Washington; occurring in scattered locations throughout North America.
Habitat: Riparian zones and adjacent fields; tolerant of alkaline.
Origin: Introduced from Eurasia
Thickleaf orach (Atriplex dioica)
Origin: Native
Tumbling orach (Atriplex rosea)
Distribution: Occurring east of the Cascades crest in Washington; British Columbia south to California, east to the Rocky Mountains; scattered locations in central and eastern U.S.
Habitat: Weedy species of irrigated land and roadsides.
Origin: Introduced from Eurasia
Garden orache (Atriplex hortensis)
Distribution: Occurring east of the Cascades crest in Washington; Alaska south to California, east to the Great Plains and in scattered locations in eastern North America.
Habitat: Disturbed areas, often where seasonally moist.
Origin: Introduced from Asia
Grassleaf orache (Atriplex littoralis)
Origin: Introduced from Europe
Halberdleaf orache (Atriplex patula)
Distribution: Occurring on both sides of the Cascades crest in Washington; occurring in scattered locations throughout North America.
Habitat: Coastal and inland, saline or alkaline soil.
Origin: Introduced from Eurasia
Hastate orache (Atriplex prostrata)
Distribution: Occurring on both sides of the Cascades crest in Washington; Washington south to California, in scattered location across Canada and the U.S. to the Atlantic Coast.
Habitat: Along the coast in saline soils, beaches, and strands; inland in alkaline soils.
Origin: Introduced from Eurasia
Long-stalked orache (Atriplex longipes)
Origin: Introduced
Narrow-leaved orache (Atriplex littoralis)
Origin: Introduced from Europe
Oblongleaf orache (Atriplex oblongifolia)
Origin: Introduced from Europe
Thin-leaf orache (Atriplex prostrata)
Distribution: Occurring on both sides of the Cascades crest in Washington; Washington south to California, in scattered location across Canada and the U.S. to the Atlantic Coast.
Habitat: Along the coast in saline soils, beaches, and strands; inland in alkaline soils.
Origin: Introduced from Eurasia
Wedge orache (Atriplex truncata)
Origin: Native
Wedgeleaf orache (Atriplex truncata)
Origin: Native
Wedgescale orache (Atriplex truncata)
Origin: Native
Spear oracle (Atriplex patula)
Distribution: Occurring on both sides of the Cascades crest in Washington; occurring in scattered locations throughout North America.
Habitat: Coastal and inland, saline or alkaline soil.
Origin: Introduced from Eurasia
Columbian mock orange (Philadelphus lewisii)
Distribution: Widely distributed throughout Washington; British Columbia south to California, east to Montana.
Habitat: Various habitats, dry to moist, sea level to 7000 feet (on the east slopes of the Cascades).
Origin: Native
Lewis' mock orange (Philadelphus lewisii)
Distribution: Widely distributed throughout Washington; British Columbia south to California, east to Montana.
Habitat: Various habitats, dry to moist, sea level to 7000 feet (on the east slopes of the Cascades).
Origin: Native
Piper's mock orange (Philadelphus lewisii)
Distribution: Widely distributed throughout Washington; British Columbia south to California, east to Montana.
Habitat: Various habitats, dry to moist, sea level to 7000 feet (on the east slopes of the Cascades).
Origin: Native
Alaska rein orchid (Piperia unalascensis)
Distribution: Widely distributed throughout Washington; Alaska south to California, east to Quebec and Colorado.
Habitat: Dry, open woods and gravelly streambanks, low to mid-elevations in the mountains.
Origin: Native
Canyon bog orchid (Platanthera stricta)
Distribution: Widely distributed throughout Washington; Alaska south to California, east to Montana and New Mexico.
Habitat: Wet meadows, swamps and coniferous forests, low to mid-elevations.
Origin: Native
Canyon bog orchid (Platanthera stricta)
Distribution: Widely distributed throughout Washington; Alaska south to California, east to Montana and New Mexico.
Habitat: Wet meadows, swamps and coniferous forests, low to mid-elevations.
Origin: Native
Choriso bog orchid (Platanthera chorisiana)
Distribution: Known only from Snohomish County in Washington; Aleutian Islands south the Vancouver Island, British Columbia, and in Snohomish County, Washington.
Habitat: Moist areas, especially at the edges of streams and bogs.
Origin: Native
Dense orchid (Piperia elongata)
Distribution: Occurring on both sides of the Cascades in Washington; British Columbia south to California, east to Idaho and Montana.
Habitat: Dry, open forest from low to middle elevations.
Origin: Native
Dense-flower rein orchid (Piperia elongata)
Distribution: Occurring on both sides of the Cascades in Washington; British Columbia south to California, east to Idaho and Montana.
Habitat: Dry, open forest from low to middle elevations.
Origin: Native
Eagle rein orchid (Platanthera aquilonis)
Distribution: Known only from Steven County in Washington; Alaska south to Oregon, east across the northern half of North America to the Atlantic Coast;
Habitat: Wet meadows from montane to subalpine.
Origin: Native
Fen orchid (Liparis loeselii)
Distribution: Occasional, Saskatchewan to Nova Scotia, south to North Dakota and Iowa; Klickitat and Yakima Counties in Washington.
Habitat: Around springs and in bogs.
Origin: Native
Large round-leaf orchid (Platanthera orbiculata)
Distribution: Alaska to Newfoundland, south on both sides of the Cascades to Oregon, Idaho and northwest Montana; east to Minnisota, Indiana and Georgia.
Habitat: Moist, mossy forests.
Origin: Native
Long-bracted orchid (Coeloglossum viride)
Distribution: Known only from Okanogan County in Washington; Alaska south to Washington, east across the southern half of Canada to the Atlantic Coast; south in the Rocky Mountains to New Mexico; east from the upper Midwest to the northeastern U.S., south in the Appalachian Mts.
Habitat: Moist to wet meadows at moderate elevations.
Origin: Native
Long-bracted orchid (Coeloglossum viride)
Distribution: Known only from Okanogan County in Washington; Alaska south to Washington, east across the southern half of Canada to the Atlantic Coast; south in the Rocky Mountains to New Mexico; east from the upper Midwest to the northeastern U.S., south in the Appalachian Mts.
Habitat: Moist to wet meadows at moderate elevations.
Origin: Native
Needle-spur green orchid (Platanthera stricta)
Distribution: Widely distributed throughout Washington; Alaska south to California, east to Montana and New Mexico.
Habitat: Wet meadows, swamps and coniferous forests, low to mid-elevations.
Origin: Native
Northern green bog orchid (Platanthera huronensis)
Distribution: Occurring chiefly east of the Cascades crest in Washington; Alaska south to Oregon, east to the Rocky Mountains; also from north-central to northeastern North America.
Habitat: Moist to boggy areas, often on limestone, low to mid-elevations.
Origin: Native
Phantom orchid (Cephalanthera austiniae)
Distribution: Both sides of the Cascades and in the Blue Mountains of Washington; British Columbia south to California, east to Idaho.
Habitat: Generally deep coniferous woods where somewhat moist.
Origin: Native
Royal rein orchid (Platanthera transversa)
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia south to California.
Habitat: Forest understory from low to middle elevations.
Origin: Native
Royal rein orchid (Platanthera transversa)
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia south to California.
Habitat: Forest understory from low to middle elevations.
Origin: Native
Sheviak's bog orchid (Platanthera aquilonis)
Distribution: Known only from Steven County in Washington; Alaska south to Oregon, east across the northern half of North America to the Atlantic Coast;
Habitat: Wet meadows from montane to subalpine.
Origin: Native
Slender bog orchid (Platanthera stricta)
Distribution: Widely distributed throughout Washington; Alaska south to California, east to Montana and New Mexico.
Habitat: Wet meadows, swamps and coniferous forests, low to mid-elevations.
Origin: Native
White-lip rein orchid (Piperia candida)
Distribution: West of the Cascades in Washington and Columbia River Gorge; Alaska to California.
Habitat: Moist coniferous forest at low elevations.
Origin: Native
Cascade Oregon-grape (Berberis nervosa)
Distribution: Occurring on both sides of the Cascades crest in Washington; southern British Columbia to California, also in northern Idaho.
Habitat: Open woods, sea level to moderate elevations in the mountains.
Origin: Native
Cascade Oregon-grape (Berberis nervosa)
Distribution: Occurring on both sides of the Cascades crest in Washington; southern British Columbia to California, also in northern Idaho.
Habitat: Open woods, sea level to moderate elevations in the mountains.
Origin: Native
Creeping Oregon-grape (Berberis repens)
Distribution: Occurring chiefly east of the Cascades crest in Washington; British Columbia south to California, east to the Rocky Mountains.
Habitat: Foothills to open forested slopes.
Origin: Nativce
Creeping Oregon-grape (Berberis repens)
Distribution: Occurring chiefly east of the Cascades crest in Washington; British Columbia south to California, east to the Rocky Mountains.
Habitat: Foothills to open forested slopes.
Origin: Nativce
Holly-leaf Oregon-grape (Berberis aquifolium)
Distribution: Widely distributed throughout Washington; southern British Columbia south to Northern California, east to northern Idaho and western Montana.
Habitat: Sagebrush slopes and open woods.
Origin: Native
Holly-leaf Oregon-grape (Berberis aquifolium)
Distribution: Widely distributed throughout Washington; southern British Columbia south to Northern California, east to northern Idaho and western Montana.
Habitat: Sagebrush slopes and open woods.
Origin: Native
Oregon-tea (Clinopodium douglasii)
Distribution: Chiefly west of the Cascade summits in Washington; Alaska south to California, east to Idaho and Montana.
Habitat: Coniferous woods, sea level to mid-elevations in the mountains.
Origin: Native
Dull Oregongrape (Berberis nervosa)
Distribution: Occurring on both sides of the Cascades crest in Washington; southern British Columbia to California, also in northern Idaho.
Habitat: Open woods, sea level to moderate elevations in the mountains.
Origin: Native
Dull Oregongrape (Berberis nervosa)
Distribution: Occurring on both sides of the Cascades crest in Washington; southern British Columbia to California, also in northern Idaho.
Habitat: Open woods, sea level to moderate elevations in the mountains.
Origin: Native
Shining Oregongrape (Berberis aquifolium)
Distribution: Widely distributed throughout Washington; southern British Columbia south to Northern California, east to northern Idaho and western Montana.
Habitat: Sagebrush slopes and open woods.
Origin: Native
Shining Oregongrape (Berberis aquifolium)
Distribution: Widely distributed throughout Washington; southern British Columbia south to Northern California, east to northern Idaho and western Montana.
Habitat: Sagebrush slopes and open woods.
Origin: Native
Tall Oregongrape (Berberis aquifolium)
Distribution: Widely distributed throughout Washington; southern British Columbia south to Northern California, east to northern Idaho and western Montana.
Habitat: Sagebrush slopes and open woods.
Origin: Native
Tall Oregongrape (Berberis aquifolium)
Distribution: Widely distributed throughout Washington; southern British Columbia south to Northern California, east to northern Idaho and western Montana.
Habitat: Sagebrush slopes and open woods.
Origin: Native
Cockscomb oreocarya (Cryptantha celosioides)
Distribution: Chiefly east of the Cascades, from southern British Colombia to Grant County, Oregon, east to North Dakota.
Habitat: Dry, open places in the valleys, plains and foothills, occasionally higher.
Origin: Native
Sheldon's oreocarya (Cryptantha celosioides)
Distribution: Chiefly east of the Cascades, from southern British Colombia to Grant County, Oregon, east to North Dakota.
Habitat: Dry, open places in the valleys, plains and foothills, occasionally higher.
Origin: Native
Linear-leaved orogenia (Orogenia linearifolia)
Distribution: Eastern Washington and Oregon, southeast to Colorado
Habitat: Open slopes and ridges, low to mid-elevations
Origin: Native
Osage-orange (Maclura pomifera)
Distribution: Introduced and established in the Snake River Canyon in Asotin County, Washington; Washington south to California, and widely established in central and eastern U.S. and Ontario, Canada.
Habitat: Open, disturbed areas.
Origin: Introduced from elsewhere in US
Purple osier (Salix purpurea)
Origin: Introduced
Oso-berry (Oemleria cerasiformis)
Distribution: Occurring west of the Cascades in Washington and along the Columbia River Gorge: British Columbia south to California.
Habitat: Moist to fairly dry, open woods at low elevations.
Origin: Native
Osoberry (Oemleria cerasiformis)
Distribution: Occurring west of the Cascades in Washington and along the Columbia River Gorge: British Columbia south to California.
Habitat: Moist to fairly dry, open woods at low elevations.
Origin: Native
Ovalpurse (Hornungia procumbens)
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia south to California, east to the Rocky Mountains, central Canada, and Newfoundland.
Habitat: Open areas where seasonally moist.
Origin: Introduced
Ovalpurse (Hornungia procumbens)
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia south to California, east to the Rocky Mountains, central Canada, and Newfoundland.
Habitat: Open areas where seasonally moist.
Origin: Introduced
Dwarf owl-clover (Triphysaria pusilla)
Distribution: West of the Cascades in Washington; British Columbia south to California.
Habitat: Vernally moist, open ground at low elevations.
Origin: Native
Golden-tongue owl-clover (Orthocarpus luteus)
Distribution: East of the Cascades in Washington; British Columbia south to California, east to Manitoba and Nebraska.
Habitat: Low ground, from the plains to moderate elevations in the mountains.
Origin: Native
Grand Coulee owl-clover (Orthocarpus barbatus)
Distribution: Southern British Columbia to Washington.
Habitat: Dry, open ground in sagebrush-steppe.
Origin: Native
Mountain owl-clover (Orthocarpus imbricatus)
Distribution: Olympic Mountains and Cascades of Washington; British Columbia south to Oregon and California.
Habitat: Fairly dry meadows and rocky slopes, mid- to high elevations in the mountains.
Origin: Native
Narrow-leaved owl-clover (Orthocarpus tenuifolius)
Distribution: East of the Cascade crest in Washington; southern British Columbia to central Oregon east to western Montana.
Habitat: Open, moist or rather dry places, from the valleys and plains to moderate elevtions in the mountains.
Origin: Native
Rosy owl-clover (Orthocarpus bracteosus)
Distribution: In Washington from the east base of the Cascades westward; southern British Columbia south to northern California.
Habitat: Meadows at low elevations.
Origin: Native
Thin-leaved owl-clover (Orthocarpus tenuifolius)
Distribution: East of the Cascade crest in Washington; southern British Columbia to central Oregon east to western Montana.
Habitat: Open, moist or rather dry places, from the valleys and plains to moderate elevtions in the mountains.
Origin: Native
Hawkweed oxtongue (Picris hieracioides)
Origin: Introduced from Europe