Burke: Polygonum polygaloides vs. Polygonum douglasii

	Polygonum polygaloides	Polygonum douglasii
		Douglas' knotweed, Douglas's knotweed
Habit	Glabrous, erect or ascending, usually freely branched annual 6-20 cm. tall.	A highly variable, simple or freely-branched, erect annual 1-4 dm. tall.
Leaves	Linear, 10-25 mm. long, 1-2 mm. broad, basally jointed; stipules lacerate, 4-8 mm. long.	Alternate and numerous along the stem, linear to oblong, lanceolate or even ovate, 1-5 cm. long, sessile, jointed at the base, reduced to bracts above; stipules sheathing, 5-15 mm. long, lacerate.
Flowers	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.	In loose, elongate racemes and in the leaf axils, 1-4 flowers per node, on pedicles 1-4 mm. long, soon reflexed; perianth 2.5-5 mm. long, the segments greenish with white, pink or reddish margins; stamens 8, occasionally fewer.
Fruits	Achene with three sharp angles, dark brown, dull, longitudinally striate, 2 mm. long.	Achene with three sharp angles, black, smooth and shining, about 3 mm. long.

	Polygonum polygaloides	Polygonum douglasii
Flowering time	June-August	June-September
Habitat	Meadows, vernal pools and rocky ridges, lowlands to mid-elevations in the mountains.	Common in dry to moist areas, lowlands to middle elevations in the mountains.
Distribution	Occurring east of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains. [WildflowerSearch map] [BONAP county map]	Occurring on both sides of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains and across the northern U.S. and Canada to the Atlantic Coast. [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. paronychia, P. parryi, P. ramosissimum, P. sawatchense, P. spergulariiforme	P. achoreum, P. austiniae, P. aviculare, P. californicum, P. erectum, P. fowleri, P. majus, P. minimum, P. nuttallii, P. paronychia, P. parryi, P. polygaloides, 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 polygaloides

Polygonum douglasii

Douglas' knotweed, Douglas's knotweed

Habit

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

A highly variable, simple or freely-branched, erect annual 1-4 dm. tall.

Leaves

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

stipules lacerate, 4-8 mm. long.

Alternate and numerous along the stem, linear to oblong, lanceolate or even ovate, 1-5 cm. long, sessile, jointed at the base, reduced to bracts above;

stipules sheathing, 5-15 mm. long, lacerate.

Flowers

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.

In loose, elongate racemes and in the leaf axils, 1-4 flowers per node, on pedicles 1-4 mm. long, soon reflexed;

perianth 2.5-5 mm. long, the segments greenish with white, pink or reddish margins;

stamens 8, occasionally fewer.

Fruits

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

Achene with three sharp angles, black, smooth and shining, about 3 mm. long.

Polygonum polygaloides

Polygonum douglasii

Flowering time

June-August

June-September

Habitat

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

Common in dry to moist areas, lowlands to middle elevations in the mountains.

Distribution

Occurring east of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains.

[WildflowerSearch map]

[BONAP county map]

Occurring on both sides of the Cascades crest in Washington; British Columbia to California, east to the Rocky Mountains and across the northern U.S. and Canada to the Atlantic Coast.

[WildflowerSearch map]

[BONAP county map]

Origin

Native

Conservation status

Not of concern

Sibling taxa