Burke: Polygonum paronychia vs. Polygonum polygaloides

	Polygonum paronychia	Polygonum polygaloides
	beach knotweed, black knotweed
Habit	Low, spreading shrub-like perennial here in Washington - typically less than 30 cm., though can get up to 100 cm. tall in some parts of its range.	Glabrous, erect or ascending, usually freely branched annual 6-20 cm. tall.
Leaves	Alternate, simple, narrow, 1-2 cm long, with prominent midrib.	Linear, 10-25 mm. long, 1-2 mm. broad, basally jointed; stipules lacerate, 4-8 mm. long.
Flowers	Small pinkish or whitish, 5-6 mm long, with 5 parts; in small clusters along stem.	Crowded in groups of 1-4 on the branch tips, the branches arising from the axils of obovate, prominent, strongly white-margined bracts that have a green mid-rib; perianth 2.5 mm. long, divided over half the length, the 5 segments oblong-lanceolate, with greenish center and prominent white to pink margins.
Fruits	Shiny black achenes 4-5 mm long.	Achene with three sharp angles, dark brown, dull, longitudinally striate, 2 mm. long.

	Polygonum paronychia	Polygonum polygaloides
Identification notes	Can be separated from other Polygonum species by its perennial decumbent stems, lacerate hyaline stipules, axillary flower clusters, and coastal habitat.
Flowering time	April-September	June-August
Habitat	Coastal shorelines and sand dunes.	Meadows, vernal pools and rocky ridges, lowlands to mid-elevations in the mountains.
Distribution	Occurring west of the Cascades crest along the coast; Vancouver Island, B.C., south to Monterey, California. [WildflowerSearch map] [BONAP county map]	Occurring east of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains. [WildflowerSearch map] [BONAP county map]
Origin	Native	Native
Conservation status	Not of concern	Not of concern
Sibling taxa	P. achoreum, P. austiniae, P. aviculare, P. californicum, P. douglasii, P. erectum, P. fowleri, P. majus, P. minimum, P. nuttallii, 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. parryi, P. ramosissimum, P. sawatchense, P. spergulariiforme
Subordinate taxa		P. polygaloides ssp. confertiflorum, P. polygaloides ssp. kelloggii, P. polygaloides ssp. polygaloides
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: 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

Polygonum paronychia

Polygonum polygaloides

beach knotweed, black knotweed

Habit

Low, spreading shrub-like perennial here in Washington - typically less than 30 cm., though can get up to 100 cm. tall in some parts of its range.

Glabrous, erect or ascending, usually freely branched annual 6-20 cm. tall.

Leaves

Alternate, simple, narrow, 1-2 cm long, with prominent midrib.

Linear, 10-25 mm. long, 1-2 mm. broad, basally jointed;

stipules lacerate, 4-8 mm. long.

Flowers

Small pinkish or whitish, 5-6 mm long, with 5 parts; in small clusters along stem.

Crowded in groups of 1-4 on the branch tips, the branches arising from the axils of obovate, prominent, strongly white-margined bracts that have a green mid-rib;

perianth 2.5 mm. long, divided over half the length, the 5 segments oblong-lanceolate, with greenish center and prominent white to pink margins.

Fruits

Shiny black achenes 4-5 mm long.

Achene with three sharp angles, dark brown, dull, longitudinally striate, 2 mm. long.

Polygonum paronychia

Polygonum polygaloides

Identification notes

Can be separated from other Polygonum species by its perennial decumbent stems, lacerate hyaline stipules, axillary flower clusters, and coastal habitat.

Flowering time

April-September

June-August

Habitat

Coastal shorelines and sand dunes.

Meadows, vernal pools and rocky ridges, lowlands to mid-elevations in the mountains.

Distribution