Burke: Polygonum douglasii vs. Polygonum heterosepalum

	Polygonum douglasii	Polygonum heterosepalum
	Douglas' knotweed, Douglas's knotweed
Habit	A highly variable, simple or freely-branched, erect annual 1-4 dm. tall.
Leaves	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	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, black, smooth and shining, about 3 mm. long.

	Polygonum douglasii	Polygonum heterosepalum
Flowering time	June-September
Habitat	Common in dry to moist areas, lowlands to middle elevations in the mountains.
Distribution	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]	[BONAP county map]
Origin	Native
Conservation status	Not of concern
Sibling taxa	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	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. polygaloides, P. ramosissimum, P. sawatchense, P. spergulariiforme
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: OR Local Web sites: 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 douglasii

Polygonum heterosepalum

Douglas' knotweed, Douglas's knotweed

Habit

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

Leaves

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

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, black, smooth and shining, about 3 mm. long.

Polygonum douglasii

Polygonum heterosepalum

Flowering time

June-September

Habitat

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

Distribution

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