Burke: Polygonum aviculare vs. Polygonum parryi

	Polygonum aviculare	Polygonum parryi
		Parry's knotweed, prickly knotweed
Habit	Highly variable species, prostrate and spreading (but not rooting at the nodes) to occasionally erect, freely-branched annual, the stems terete, striate, up to 1 m. long.
Leaves	Numerous, bluish-green, only slightly reduced upward, narrowly oblong, 1-3 cm. long and 2-6 mm. broad, narrowed to a very short, jointed petiole; stipules lacerate, 3-6 mm. long.
Flowers	1-3 in the axils of the leaves or leaf-like bracts, the pedicles 1-3 mm. long, erect; perianth 2.5 mm. long, divided 2/3 the length, the segments 5, oblong, sub-equal, greenish with white to pink or red margins.
Fruits	Achene with 3 sharp angles, brownish, smooth.

	Polygonum aviculare	Polygonum parryi
Flowering time	May-October	June-July
Habitat	Dry or slightly moist, disturbed soil, often where hard-packed.	Vernal pools, seasonally damp ground at low elevations.
Distribution	Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast. [WildflowerSearch map] [BONAP county map]	Occurring in the east end of the Columbia River Gorge in Washington; south-central Washington to California. [WildflowerSearch map] [BONAP county map]
Origin	Both native and introduced	Native
Conservation status	Not of concern	Threatened in Washington (WANHP)
Sibling taxa	P. achoreum, P. austiniae, P. californicum, P. douglasii, P. erectum, P. fowleri, P. majus, P. minimum, P. nuttallii, P. paronychia, P. parryi, P. polygaloides, P. ramosissimum, P. sawatchense, P. spergulariiforme	P. achoreum, P. austiniae, P. aviculare, P. californicum, P. douglasii, P. erectum, P. fowleri, P. majus, P. minimum, P. nuttallii, P. paronychia, P. polygaloides, P. ramosissimum, P. sawatchense, P. spergulariiforme
Subordinate taxa	P. aviculare ssp. aviculare, P. aviculare ssp. buxiforme, P. aviculare ssp. depressum, P. aviculare ssp. neglectum
Web links	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria, Turner Photog. WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Polygonum aviculare

Polygonum parryi

Parry's knotweed, prickly knotweed

Habit

Highly variable species, prostrate and spreading (but not rooting at the nodes) to occasionally erect, freely-branched annual, the stems terete, striate, up to 1 m. long.

Leaves

Numerous, bluish-green, only slightly reduced upward, narrowly oblong, 1-3 cm. long and 2-6 mm. broad, narrowed to a very short, jointed petiole;

stipules lacerate, 3-6 mm. long.

Flowers

1-3 in the axils of the leaves or leaf-like bracts, the pedicles 1-3 mm. long, erect;

perianth 2.5 mm. long, divided 2/3 the length, the segments 5, oblong, sub-equal, greenish with white to pink or red margins.

Fruits

Achene with 3 sharp angles, brownish, smooth.