Burke: Polygonum aviculare vs. Polygonum spergulariiforme

	Polygonum aviculare	Polygonum spergulariiforme
		fall knotweed, spurry 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.	Erect to rounded annual, the stems simple or freely-branched, up to 5 dm. tall, the branches wiry, sharply angled above.
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.	Leaves alternate, basally jointed, linear to narrowly oblong-oblanceolate, 1-3 cm. long and 1-2 mm. wide; stipules sheathing, 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.	Flowers 1-4 in the axils of the upper leaves and crowded, leaf-like bracts which exceed the flowers; pedicles slender, 1-2 mm. long; the 5 perianth segments 3-4 mm. long, attached 1/3 their length, pinkish with a green midrib; stamens 8; styles 3, 0.5 mm. long.
Fruits	Achene with 3 sharp angles, brownish, smooth.	Achene 3-angled, 3-4 mm. long, black, shining and smooth.

	Polygonum aviculare	Polygonum spergulariiforme
Flowering time	May-October	June-September
Habitat	Dry or slightly moist, disturbed soil, often where hard-packed.	Balds, prairies, and headlands in gravelly, sandy or heavy, dry or moist soil 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 west of the Cascades crest and east in the Columbia River Gorge in Washington; British Columbia to California, east to Idaho, Montana, and Wyoming. [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. douglasii, P. erectum, P. fowleri, P. majus, P. minimum, P. nuttallii, P. paronychia, P. parryi, P. polygaloides, P. ramosissimum, P. sawatchense
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 WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Polygonum spergulariiforme

fall knotweed, spurry 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.

Erect to rounded annual, the stems simple or freely-branched, up to 5 dm. tall, the branches wiry, sharply angled above.

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.

Leaves alternate, basally jointed, linear to narrowly oblong-oblanceolate, 1-3 cm. long and 1-2 mm. wide;

stipules sheathing, 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.

Flowers 1-4 in the axils of the upper leaves and crowded, leaf-like bracts which exceed the flowers; pedicles slender, 1-2 mm. long; the 5 perianth segments 3-4 mm. long, attached 1/3 their length, pinkish with a green midrib;

stamens 8;

styles 3, 0.5 mm. long.

Fruits

Achene with 3 sharp angles, brownish, smooth.

Achene 3-angled, 3-4 mm. long, black, shining and smooth.

Polygonum aviculare

Polygonum spergulariiforme

Flowering time

May-October

June-September

Habitat

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

Balds, prairies, and headlands in gravelly, sandy or heavy, dry or moist soil 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 west of the Cascades crest and east in the Columbia River Gorge in Washington; British Columbia to California, east to Idaho, Montana, and Wyoming.

[WildflowerSearch map]

[BONAP county map]

Origin

Both native and introduced

Native

Conservation status

Not of concern

Sibling taxa