Davis' Knotweed, Newberry's Fleeceflower, Newberry's Knotweed: Koenigia davisiae var. davisiae (Synonyms: Aconogonon davisiae, Aconogonon davisiae var. davisiae, Aconogonon davisiae var. glabrum, Polygonum davisiae, Polygonum newberryi, Polygonum newberryi var. glabrum, Polygonum newberryi var. newberryi) - This is a recent name change for this taxon in Oregon. WTU Herbarium in Washington still considers this as Aconogonon davisiae. It is only found east of the main Cascade Mountain alignment in the Wenatchee Mountains of Washington.
Alpine Fleeceflower, Alpine Knotweed, Jimson Knotweed, Poke Fleeceflower, Poke Knotweed: Koenigia phytolaccifolia (Synonyms: Aconogonon phytolacifolium, Aconogonon phytolaccifolium var. glabrum, Aconogonon phytolaccifolium var. phytolaccifolium, Polygonum phytolaccifolium) - This is the currently accepted name for this taxon in Oregon. WTU Herbarium in Washington still considers this as Aconogonon phytolaccifolium var. phytolaccifolium. I've kept the links to the two varieties immediately below for the time being.
Smooth Alpine Knotweed: Aconogonon phytolaccifolium var. glabrum (Synonym: Polygonum phytolaccifolium)
Alpine Knotweed, Jimson Knotweed, Pokeweed Fleeceflower: Aconogonon phytolaccifolium var. phytolaccifolium (Synonym: Polygonum phytolaccifolium)
American Bistort, Snakeweed, Mountain Meadow Knotweed, Western Bistort: Bistorta bistortoides (Synonyms: Persicaria bistortoides, Polygonum bistortoides, Polygonum bistortoides var. linearifolium, Polygonum bistortoides var. oblongifolium, Polygonum cephalophorum, Polygonum glastifolium, Polygonum vulcanicum)
Garden Buckwheat: Fagopyrum esculentum (Synonyms: Fagopyrum sagittatum, Fagopyrum vulgare, Polygonum fagopyrum)
Bohemian Knotweed: Fallopia x bohemica (Synonym: Polygonum x bohemicum)
Climbing Bindweed, Black Bindweed: Fallopia convolvulus (Synonyms: Polygonum convolvulus, Polygonum convolvulus var. convolvulus) - Stems vine-like and twining. Leaves heart-shaped.
Japanese Knotweed: Fallopia japonica (Synonym: Polygonum cuspidatum)
Giant Knotweed: Fallopia sachalinensis (Synonym: Polygonum sachalinense)
Water Smartweed, Pink Smartweed: Persicaria amphibia (Synonyms: Polygonum amphibium, Polygonum amphibium var. coccineum, Polygonum amphibium var. emersum, Polygonum amphibium var. natans, Polygonum amphibium var. stipulaceum, Polygonum coccineum, Polygonum coccineum var. coccineum, Polygonum coccineum var. hartwrightii, Polygonum natans, Polygonum natans var. hartwrightii)
Smartweed, Marshpepper Smartweed: Persicaria hydropiper (Synonyms: Polygonum hydropiper, Polygonum hydropiper var. projectum)
Waterpepper: Persicaria hydropiperoides (Synonyms: Polygonum hydropiperoides, Polygonum hydropiperoides var. asperifolium, Polygonum hydropiperoides var. hydropiperoides, Polygonum hydropiperoides var. psilostachyum, Polygonum persicarioides)
Curltop Ladysthumb, Pale Smartweed, Willowweed, Willow-weed: Persicaria lapathifolia (Synonym: Polygonum lapathifolium, Polygonum lapathifolium var. lapathifolium, Polygonum lapathifolium var. incanum, Polygonum lapathifolium var. nodosum, Polygonum lapathifolium var. salicifolium)
Spotted Ladysthumb, Spotted Lady's-thumb, Heartweed, Redshank: Persicaria maculosa (Synonym: Polygonum persicaria)
Dotted Smartweed, Water Smartweed: Persicaria punctata (Synonyms: Polygonum acre, Polygonum acre var. leptostachyum, Polygonum punctatum, Polygonum punctatum var. confertiflorum, Polygonum punctatum var. ellipticum, Polygonum punctatum var. punctatum, Polygonum punctatum var. leptostachyum)
Blake's Knotweed, Leathery Knotweed: Polygonum achoreum (Synonym: Polygonum erectum ssp. achoreum)
Austin's Knotweed: Polygonum austiniae (Synonym: Polygonum douglasii ssp. austiniae, Polygonum douglasii var. austiniae)
Doorweed, Prostrate Knotweed: Polygonum aviculare (P. arenastrum)
California Knotweed: Polygonum californicum
Cascade Knotweed: Polygonum cascadense
Douglas' Knotweed: Polygonum douglasii (Synonyms: Polygonum buxiforme var. montanum, Polygonum douglasii ssp. douglasii, Polygonum douglasii var. douglasii, Polygonum douglasii var. latifolium, Polygonum emaciatum, Polygonum montanum)
Erect Knotweed: Polygonum erectum
Gabriela's Knotweed: Polygonum gabrielae
Dwarf Desert Knotweed: Polygonum heterosepalum
Wiry Knotweed: Polygonum majus
Broadleaf Knotweed, Broad-leaved Knotweed, Leafy Dwarf Knotweed, Zigzag Knotweed: Polygonum minimum (Synonym: Polygonum torreyi)
Nuttall's Knotweed: Polygonum nuttallii - From the eastern foothills of the Oregon Cascades and west as well as in the Okanogan.
Parry's Knotweed: Polygonum parryi
Closeflowered Knotweed, Close-flowered Knotweed, Fruitleaf Knotweed: Polygonum polygaloides ssp. confertiflorum (Synonyms: Polygonum confertiflorum, Polygonum imbricatum, Polygonum kelloggii var. confertiflorum, Polygonum watsonii)
Kellogg's Knotweed: Polygonum polygaloides ssp. kelloggii (Synonyms: Polygonum kelloggii, Polygonum minutissimum, Polygonum unifolium)
Pokeweed Fleeceflower, White-margined Knotweed: Polygonum polygaloides ssp. polygaloides (Synonyms: Polygonum confertiflorum, Polygonum kelloggii, Polygonum kelloggii var. confertiflorum, Polygonum watsonii)
Bushy Knotweed, Yellow-flowered Knotweed: Polygonum ramosissimum ssp. ramosissimum
Sawatch Knotweed: Polygonum sawatchense (Synonyms: Polygonum douglasii ssp. johnstonii, Polygonum sawatchense ssp. oblivium, Polygonum douglasii var. johnstonii)
Fall Knotweed, Spurry Knotweed: Polygonum spergulariiforme (Synonyms: Polygonum douglasii ssp. spergulariiforme, Polygonum emaciatum, Polygonum spergulariaeforme)
Alpine Bistort: Polygonum viviparum