Vascular Plants

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Scientific names beginning with O:
25 genera
49 species, 16 subspecies and varieties
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Odontites vulgarisred bartsia
Oemleria cerasiformisoso-berry, osoberry
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.
Oenanthe sarmentosaPacific water-dropwort, American water-parsley
Distribution: West of the Cascades from British Columbia south to California.
Habitat: Low elevations; wet areas, often is standing water.
Oenothera biennisking's-cureall
Distribution: Occurring on both sides of the Cascades crest in Washington; widely distributed throughout much of North America.
Habitat: Meadows and stream banks, from the plains to the lower mountains, typically where disturbed.
Oenothera cespitosa
Distribution: Occuring sporadically throughout central and eastern Washington; widespread throughout much of western U.S. and central Canada.
Habitat: Talus slopes, road cuts, and dry hills.
ssp. cespitosa – butte primrose, fragrant evening primrose, rock rose
Oenothera curtiflorasmall-flowered gaura, velvetweed, velvet weed
Distribution: Occurring east of the Cascades crest in Washington; widely distributed throughout North America.
Habitat: Open, sandy, rocky, often disturbed places.
Oenothera elata
Distribution: Occurring chiefly east of the Cascades crest in Washington; Washington south to California, east to the Rocky Mountains and southern Great Plains in the U.S.
Habitat: Sagebrush hills to mid elevations in the mountains, generally where moist.
ssp. hirsutissima – Hooker's evening primrose
Oenothera flava
Distribution: Known historically in Washington from south-central part of the state; Saskatchewan to Mexico, west to Idaho and California.
Habitat: Hard-packed soil in swales or around vernal pools in the plains and lower foothills.
ssp. flava – long-tubed evening primrose
Oenothera glaziovianared-sepal evening-primrose
Distribution: Occasional garden escape west of the Cascades in Washington; British Columbia south to California.
Habitat: Disturbed soil.
Oenothera pallida
Distribution: Occurring east of the Cascades crest in Washington; British Columbia south to Arizona, east to the Rocky Mountains and Texas.
Habitat: Dry, sandy or gravelly soil, commonly on dunes at low elevations.
ssp. pallida – pale evening primrose
Oenothera villosa
Distribution: Widely distributed throughout Washington; widely distributed throughout North America.
Habitat: Forest openings, often where moist.
ssp. strigosa – common evening primrose
Olsynium douglasii
Distribution: Widely distributed throughout Washington, but more common east of the Cascades crest; British Columbia south to California, east to Idaho, Nevada, and Utah.
Habitat: Coastal bluffs, prairies, open rocky areas, oak and ponderosa pine woodlands, sagebrush and juniper desert, where moist in early spring.
var. douglasii – grass widows
var. inflatum – purple-eyed grass, grass widows
Onobrychis viciifoliaholy-clover, saintfoin, sandfain
Distribution: Occasionally introduced in scattered locations throughout Washington; ranging throughout western North America and parts of central and eastern North America.
Habitat: Waste ground, disturbed soil.
Ononis repenscommon restharrow
Onopordum acanthiumcotton thistle, Scotch thistle, Scots thistle
Distribution: Chiefly east of the Cascades in Washington, but also on the west side; introduced throughout nearly all of North America.
Habitat: Noxious weed of dry, open areas and stream banks.
Ophioglossum pusillumnorthern adder's-tongue
Distribution: Alaska to California, and Montana east to Maine and Virginia
Habitat: Meadows and woods at moderate elevations in the mountains
Oplopanax horridusdevil's club, devil's-club
Distribution: Widely distributed throughout the forested areas of Washington; Alaska south to Oregon, east to Ontario.
Habitat: Moist woods at mid-elevations, especially along streams.
Opuntia ×columbianaColumbia prickly pear
Distribution: Occurring east of the Cascades in Washington; southern British Columbia south to eastern Oregon.
Habitat: Plains and foothills to the lower mountains.
Opuntia fragilisbrittle prickly-pear, little prickly-pear
Distribution: British Columbia to California, east to Michigan and Texas
Habitat: Dry, open, often sandy soil
Oreostemma alpigenum
Distribution: Alpine areas of Olympic and Cascade Mountains; British Columbia to California, east to Wyoming.
Habitat: High mountain meadows.
var. alpigenum – alpine aster, tundra mountaincrown
Origanum vulgarewild marjoram
Distribution: West of the Cascades in Washington; introduced from Eurasia into northeastern United States.
Habitat: Escaped from cultivation along roadsides and in disturbed soil.
Ornithogalum umbellatumnap-at-noon, sleepydick
Distribution: Distributed in scattered locations throughout Washington; occurring chiefly in central and eastern United States, with scattered locations in western states.
Habitat: Roadsides, open forests, waste places.
Orobanche minorhellroot
Distribution: Occurring only sparingly, west of the Cascades in Washington; Washington south to Oregon; along the Atlantic Coast of the U.S.
Habitat: Lowland areas, parasitic, especially on clover.
Orogenia linearifoliaGreat Basin Indian-potato, linear-leaved orogenia
Distribution: Eastern Washington and Oregon, southeast to Colorado
Habitat: Open slopes and ridges, low to mid-elevations
Orthilia secundaone-sided pyrola, sidebells
Distribution: Alaska to California, east to New Mexico in the west, and across the northern half of the United States to the Atlantic
Habitat: Common in coniferous woods at moderate to mid-elevationn in the mountains
Orthocarpus barbatusGrand Coulee owl-clover
Distribution: Occurring east of the Cascades crest in Washington. Southern British Columbia to Washington.
Habitat: Dry, open ground in sagebrush-steppe.
Orthocarpus bracteosusrosy owl-clover
Distribution: In Washington from the east base of the Cascades westward; southern British Columbia south to northern California.
Habitat: Meadows at low elevations.
Orthocarpus imbricatusmountain owl-clover
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.
Orthocarpus luteusgolden-tongue owl-clover
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.
Orthocarpus tenuifoliusnarrow-leaved owl-clover, thin-leaved owl-clover
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.
Oryzopsis asperifoliawhite-grain mountain-rice grass
Distribution: British Columbia east to Newfoundland, south to Maine and Montana and the northeast portion of Washington.
Habitat: Open coniferous woods.
Osmorhiza berteroiChilean sweet-cicely, mountain sweet-cicely
Distribution: Widely distributed throughout much of Washington; southern Alaska to California, east to South Dakota and Arizona.
Habitat: Woodlands, from near sea level to moderate elevations in the mountains.
Osmorhiza depauperatablunt-fruit sweet-cicely
Osmorhiza occidentalisSierran sweet-cicely, western sweet-cicely
Distribution: Occurring chiefly east of the Cascades in Washington; British Columbia south to California, east to the Rocky Mountains.
Habitat: Low to mid-elevations in open areas and openings in wooded areas.
Osmorhiza purpureapurple sweet-cicely
Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska south to California, east to Alberta, Idaho, and Montana.
Habitat: Moist areas at mid-elevations in the mountains.
Oxalis corniculatacreeping yellow wood-sorrel
Distribution: Scattered locations throughout Washington; distributed widely throughout North America.
Habitat: A weed of gardens, disturbed areas, and waste places.
Oxalis dilleniislender yellow wood-sorrel
Distribution: Occurring on both sides of the Cascades crest in Washington; Washington south to Oregon, east across North America to the Atlantic Coast.
Habitat: Open areas, often where moist, at low elevations.
Oxalis oreganaredwood-sorrel, Oregon wood-sorrel
Distribution: Olympic Mountains and west slope of the Cascades in Washington; British Columbia south to California.
Habitat: Moist woods, low to moderate elevations.
Oxalis strictaupright yellow wood-sorrel
Distribution: Distributed on both sides of the Cascades in Washington, more common west of the Cascades; widely distributed throughout North America.
Habitat: Disturbed ground, lawns and gardens.
Oxalis suksdorfiiwestern yellow wood-sorrel
Distribution: West of the Casccades in Washington; southern Washington to northwest California.
Habitat: Low elevations, usually in moist, coastal woods but sometimes on rather dry, open slopes.
Oxalis trilliifoliagreat wood-sorrel, trillium-leaf wood-sorrel
Distribution: West slope of the Cascades in Washington; Washington south to northwest California.
Habitat: Meadows and moist woods in the coastal mountains and up to 6000 feet in the Cascades.
Oxyria digynamountain-sorrel
Distribution: Alaska to California, east to Montana, Colorado and New Mexico; also across Canada to Labrador, and the Olympics in Washington
Habitat: Moist, usually rocky ground, alpine to subalpine
Oxytheca dendroidea
ssp. dendroidea – treeline puncturebract
Oxytropis borealis
Distribution: Alaska to Quebec, south chiefly in the Rocky Mountains to Colorado, west to the Sierra Nevada of California, the Wallowas of Oregon and the Olympics of Washington.
Habitat: Alpine and subalpine habitats.
var. viscida – sticky crazyweed
Oxytropis campestris
Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska south to Oregon, east to Wisconsin and Quebec, south in the Rockies to Colorado.
Habitat: Forest openings and rocky balds from sea-level to the alpine.
var. columbiana – slender crazyweed
var. cusickii – slender crazyweed
var. gracilis – yellow-flower locoweed
var. wanapum – wanapum crazyweed
Oxytropis deflexa
Distribution: Occurring in north-central Washington; widely distributed throughout western North America and across Canada.
Habitat: Forest openings and meadows at moderate elevations in the mountains.
var. sericea – pendant-pod crazyweed
Ozomelis diversifoliaangle-leaf bishop's-cap
Distribution: Occurring from in southern Cascade Mountains from Mt. Adams south in Washington; Washington south to the Trinity Mountains of northwest California.
Habitat: Moist woods and stream banks at moderate to high elevations.
Ozomelis stauropetalacross-shaped mitrewort, side-flowered mitrewort
Distribution: Occurring east of the Cascades crest in Washington; Washington south to Oregon, east to Idaho, Montana, Wyoming, Colorado and Utah.
Habitat: Open to dense moist woods at mid-elevations in the mountains.
Ozomelis trifidathree-toothed mitrewort
Distribution: Occurring in the Olympic Mountains and on both sides of the Cascades crest in Washington; British Columbia south to California, east to Alberta, Montana, and Idaho.
Habitat: Moist forests, moderate to mid-elevations in the mountains.