Polygonum
doorweed, knotweed, smartweed
17 species
12 subspecies and varieties
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Common name
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Polygonum achoreumBlake's knotweed
Origin: Native
Polygonum austiniaeAustin's knotweed
Distribution: Central Oregon to northeast California, east to Idaho and southcentral Montana.
Habitat: Dry to moist banks and flats, from sagebrush plains to lower mountains, often with ponderosa pine.
Origin: Native
Flowers: June - August
Polygonum aviculare
Distribution: An introduced, ubiquitous weed, found throughout the United States.
Habitat: Dry or slightly moist, disturbed soil, often where hard-packed.
Origin: Both native and introduced
Flowers: July - September
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 californicumCalifornia knotweed
Origin: Native
Flowers: July - September
Polygonum douglasiiDouglas' knotweed, Douglas's knotweed
Distribution: Widely distributed throughout most of Washington; British Columbia south to California, east to the Rocky Mountains and across northern U.S./southern Canada to the Atlantic Coast.
Habitat: Common in dry to moist areas, lowlands to mid-elevations in the mountains.
Origin: Native
Flowers: June-September
Polygonum erectumerect knotweed
Origin: Native
Flowers: June - September
Polygonum fowleriFowler's knotweed
Distribution: Occurring west of the Cascades in Washington; Alaska south to California, east across northern Canada to northeastern North America.
Habitat: Coastal salt marshes.
Origin: Native
Flowers: July-November
ssp. fowleri – Fowler's knotweed
Polygonum majusPalouse knotweed, wiry knotweed
Distribution: Occurring east of the Cascades crest in Washington; British Columbia south 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
Polygonum minimumleafy dwarf knotweed, zigzag knotweed
Distribution: British Columbia south in the Cascades and higher coastal mountains to the southern Sierra Navada, east in the Rockies from Montana to Colorado.
Habitat: Open or semi-barren soil in the alpine and subalpine.
Origin: Native
Flowers: July - September
Polygonum nuttalliiNuttall's knotweed
Distribution: Occurring chiefly west of the Cascades crest in Washington; British Columbia south to Oregon
Habitat: Prairies, grassy balds, and forest openings at low to moderate elevations.
Origin: Native
Flowers: May-July
Polygonum paronychiabeach 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
Polygonum parryiParry's knotweed
Origin: Native
Flowers: June - July
Polygonum patulum
Origin: Introduced
Polygonum polygaloides
Distribution: Occurring east of the Cascades crest in Washington; British Columbia south 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
ssp. confertiflorum – close-flowered knotweed
ssp. kelloggii – white-margin knotweed
ssp. polygaloides – Polygala knotweed
Polygonum ramosissimum
Distribution: Occurring chiefly east of the Cascades crest in Washington; widely distributed throughout North America.
Habitat: Disturbed areas, often where wet, from low to middle elevations.
Origin: Native
Flowers: July-September
ssp. prolificum – proliferous knotweed
ssp. ramosissimum – bushy knotweed
Polygonum sawatchense
Distribution: Occurring east of the Cascades crest in Washington; British Columbia south 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
ssp. oblivium – Sawatch knotweed
ssp. sawatchense – Sawatch knotweed
Polygonum spergulariiformefall knotweed, spurry knotweed
Distribution: British Columbia to California, chiefly west of the Cascades in Washington, east to southeast Washington, Idaho and Colorado.
Habitat: Gravelly, sandy or heavy dry or moist soil at low elevations.
Origin: Native
Flowers: June - September