1 genus
16 species, 12 subspecies and varieties
16 species, 12 subspecies and varieties
Display as:
Polygonum achoreum – Blake's knotweed
Distribution: Reported for Washington, but specimen from Pierce County is likely a misidentification; Alaska to Oregon and Nevada, east across North America to the Atlantic Coast.
Habitat: Disturbed areas.
Origin: Native
Flowers: May-July
Growth Duration: Annual
Distribution: Reported for Washington, but specimen from Pierce County is likely a misidentification; Alaska to Oregon and Nevada, east across North America to the Atlantic Coast.
Habitat: Disturbed areas.
Origin: Native
Flowers: May-July
Growth Duration: Annual
Polygonum austiniae – Austin's knotweed
Distribution: Occurring east of the Cascades crest in Washington; British Columbia to California, east to Alberta and Wyoming.
Habitat: Dry to moist banks and flats, from sagebrush plains to lower mountains, often with ponderosa pine.
Origin: Native
Flowers: June-August
Growth Duration: Annual
Distribution: Occurring east of the Cascades crest in Washington; British Columbia to California, east to Alberta and Wyoming.
Habitat: Dry to moist banks and flats, from sagebrush plains to lower mountains, often with ponderosa pine.
Origin: Native
Flowers: June-August
Growth Duration: Annual
Polygonum aviculare – common knotweed
Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast.
Habitat: Dry or slightly moist, disturbed soil, often where hard-packed.
Origin: Both native and introduced
Flowers: May-October
Growth Duration: Annual
Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast.
Habitat: Dry or slightly moist, disturbed soil, often where hard-packed.
Origin: Both native and introduced
Flowers: May-October
Growth Duration: Annual
• ssp. aviculare – common knotweed, yard knotweed
• ssp. buxiforme – American knotweed, prairie knotweed
• ssp. depressum – common knotweed, oval-leaf knotweed
• ssp. neglectum – narrow-leaf knotweed
Polygonum californicum – California knotweed
Distribution: Occurring in the east end of the Columbia River Gorge in Washington; south-central Washington to California.
Habitat: Dry rocky slopes, gravelly ground at low elevations.
Origin: Native
Flowers: May-July
Growth Duration: Annual
Distribution: Occurring in the east end of the Columbia River Gorge in Washington; south-central Washington to California.
Habitat: Dry rocky slopes, gravelly ground at low elevations.
Origin: Native
Flowers: May-July
Growth Duration: Annual
Polygonum douglasii – Douglas' knotweed, Douglas's knotweed
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains and across the northern U.S. and Canada to the Atlantic Coast.
Habitat: Common in dry to moist areas, lowlands to middle elevations in the mountains.
Origin: Native
Flowers: June-September
Growth Duration: Annual
Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains and across the northern U.S. and Canada to the Atlantic Coast.
Habitat: Common in dry to moist areas, lowlands to middle elevations in the mountains.
Origin: Native
Flowers: June-September
Growth Duration: Annual
Polygonum erectum – erect knotweed
Distribution: Occurring on both sides of the Cascades crest in Washington; Washington to Oregon and Nevada, east from the Rocky Mountains and northern Great Plains to the Altantic Coast.
Habitat: Dry, disturbed ground.
Origin: Native
Flowers: June-September
Growth Duration: Annual
Distribution: Occurring on both sides of the Cascades crest in Washington; Washington to Oregon and Nevada, east from the Rocky Mountains and northern Great Plains to the Altantic Coast.
Habitat: Dry, disturbed ground.
Origin: Native
Flowers: June-September
Growth Duration: Annual
Polygonum fowleri – Fowler's knotweed
Distribution: Occurring west of the Cascades crest in Washington; Alaska to California, east across Canada to northeastern North America.
Habitat: Coastal salt marshes.
Origin: Native
Flowers: July-November
Growth Duration: Annual
Distribution: Occurring west of the Cascades crest in Washington; Alaska to California, east across Canada to northeastern North America.
Habitat: Coastal salt marshes.
Origin: Native
Flowers: July-November
Growth Duration: Annual
• ssp. fowleri – Fowler's knotweed
Polygonum majus – Palouse knotweed, wiry knotweed
Distribution: Occurring chiefly east of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains.
Habitat: Dry, often semi-barren, gravelly to heavy soil, sagebrush desert to lower mountains.
Origin: Native
Flowers: May-August
Growth Duration: Annual
Distribution: Occurring chiefly east of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains.
Habitat: Dry, often semi-barren, gravelly to heavy soil, sagebrush desert to lower mountains.
Origin: Native
Flowers: May-August
Growth Duration: Annual
Polygonum minimum – leafy dwarf knotweed, zigzag knotweed
Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east to the Rocky Mountains.
Habitat: Open or semi-barren soil in the alpine and subalpine.
Origin: Native
Flowers: July-September
Growth Duration: Annual
Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east to the Rocky Mountains.
Habitat: Open or semi-barren soil in the alpine and subalpine.
Origin: Native
Flowers: July-September
Growth Duration: Annual
Polygonum nuttallii – Nuttall's knotweed
Distribution: Occurring chiefly west of the Cascades crest in Washington; British Columbia to Oregon, east to Idaho.
Habitat: Prairies, grassy balds, and forest openings at low to moderate elevations.
Origin: Native
Flowers: May-July
Growth Duration: Annual
Distribution: Occurring chiefly west of the Cascades crest in Washington; British Columbia to Oregon, east to Idaho.
Habitat: Prairies, grassy balds, and forest openings at low to moderate elevations.
Origin: Native
Flowers: May-July
Growth Duration: Annual
Polygonum paronychia – beach knotweed, black knotweed
Distribution: Occurring west of the Cascades crest along the coast; Vancouver Island, B.C., south to Monterey, California.
Habitat: Coastal shorelines and sand dunes.
Origin: Native
Flowers: April-September
Growth Duration: Perennial
Distribution: Occurring west of the Cascades crest along the coast; Vancouver Island, B.C., south to Monterey, California.
Habitat: Coastal shorelines and sand dunes.
Origin: Native
Flowers: April-September
Growth Duration: Perennial
Polygonum parryi – Parry's knotweed, prickly knotweed
Distribution: Occurring in the east end of the Columbia River Gorge in Washington; south-central Washington to California.
Habitat: Vernal pools, seasonally damp ground at low elevations.
Origin: Native
Flowers: June-July
Growth Duration: Annual
Distribution: Occurring in the east end of the Columbia River Gorge in Washington; south-central Washington to California.
Habitat: Vernal pools, seasonally damp ground at low elevations.
Origin: Native
Flowers: June-July
Growth Duration: Annual
Polygonum polygaloides – white-margined knotweed
Distribution: Occurring east of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains.
Habitat: Meadows, vernal pools and rocky ridges, lowlands to mid-elevations in the mountains.
Origin: Native
Flowers: June-August
Growth Duration: Annual
Distribution: Occurring east of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains.
Habitat: Meadows, vernal pools and rocky ridges, lowlands to mid-elevations in the mountains.
Origin: Native
Flowers: June-August
Growth Duration: Annual
• ssp. confertiflorum – close-flowered knotweed
• ssp. kelloggii – white-margin knotweed
• ssp. polygaloides – pokeweed fleeceflower, white-margined knotweed
Polygonum ramosissimum – branched knotweed
Distribution: Occurring chiefly east of the Cascades crest in Washington; British Columbia to California, east across North America to the Atlantic Coast.
Habitat: Disturbed areas, often where wet, from low to middle elevations.
Origin: Native
Flowers: July-September
Growth Duration: Annual
Distribution: Occurring chiefly east of the Cascades crest in Washington; British Columbia to California, east across North America to the Atlantic Coast.
Habitat: Disturbed areas, often where wet, from low to middle elevations.
Origin: Native
Flowers: July-September
Growth Duration: Annual
• ssp. prolificum – proliferous knotweed
• ssp. ramosissimum – bushy knotweed
Polygonum sawatchense – Sawatch knotweed
Distribution: Occurring east of the Cascades crest in Washington; British Columbia to California, east to the Great Plains.
Habitat: Dry to moist forest openings and meadows from moderate elevations to the subalpine.
Origin: Native
Flowers: June-August
Growth Duration: Annual
Distribution: Occurring east of the Cascades crest in Washington; British Columbia to California, east to the Great Plains.
Habitat: Dry to moist forest openings and meadows from moderate elevations to the subalpine.
Origin: Native
Flowers: June-August
Growth Duration: Annual
• ssp. oblivium – sublime knotweed
• ssp. sawatchense – Sawatch knotweed
Polygonum spergulariiforme – fall knotweed, spurry knotweed
Distribution: Occurring west of the Cascades crest and east in the Columbia River Gorge in Washington; British Columbia to California, east to Idaho, Montana, and Wyoming.
Habitat: Balds, prairies, and headlands in gravelly, sandy or heavy, dry or moist soil at low elevations.
Origin: Native
Flowers: June-September
Growth Duration: Annual
Distribution: Occurring west of the Cascades crest and east in the Columbia River Gorge in Washington; British Columbia to California, east to Idaho, Montana, and Wyoming.
Habitat: Balds, prairies, and headlands in gravelly, sandy or heavy, dry or moist soil at low elevations.
Origin: Native
Flowers: June-September
Growth Duration: Annual
