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)

Water Smartweed: Polygonum amphibium

Doorweed, Prostrate Knotweed: Polygonum aviculare (P. arenastrum)

California Knotweed: Polygonum californicum

Pink Knotweed: Polygonum coccineum

Climbing Bindweed, Black Bindweed: Polygonum convolvulus - Stems vine-like and twining. Leaves heart-shaped.

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)

Dwarf Desert Knotweed: Polygonum heterosepalum

Smartweed, Marshpepper Smartweed: Polygonum hydropiper

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)

Willow Weed: Polygonum lapathifolium

Wiry Knotweed: Polygonum majus

Broadleaf Knotweed, Broad-leaved Knotweed, Leafy Dwarf Knotweed, Zigzag Knotweed: Polygonum minimum (Synonym: Polygonum torreyi)

Spotted Ladysthumb: Polygonum persicaria

Alpine Knotweed: Polygonum phytolaccaefolium

White-margined Knotweed: Polygonum polygaloides

Sawatch Knotweed: Polygonum sawatchense

Alpine Bistort: Polygonum viviparum