Burke: Polygonum aviculare vs. Polygonum douglasii

	Polygonum aviculare	Polygonum douglasii
		Douglas' knotweed, Douglas's 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.	A highly variable, simple or freely-branched, erect annual 1-4 dm. tall.
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.	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	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.	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 3 sharp angles, brownish, smooth.	Achene with three sharp angles, black, smooth and shining, about 3 mm. long.

	Polygonum aviculare	Polygonum douglasii
Flowering time	May-October	June-September
Habitat	Dry or slightly moist, disturbed soil, often where hard-packed.	Common in dry to moist areas, lowlands to middle elevations in the mountains.
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 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	Both native and introduced	Native
Conservation status	Not of concern	Not of concern
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. erectum, P. fowleri, P. majus, P. minimum, P. nuttallii, P. paronychia, P. parryi, 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: 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 aviculare

Polygonum douglasii

Douglas' knotweed, Douglas's 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.

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

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.

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

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.

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 3 sharp angles, brownish, smooth.

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

Polygonum aviculare

Polygonum douglasii

Flowering time

May-October

June-September

Habitat

Dry or slightly moist, disturbed soil, often where hard-packed.

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

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 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

Both native and introduced

Native

Conservation status

Not of concern

Sibling taxa