Burke: Persicaria hydropiperoides vs. Persicaria wallichii

	Persicaria hydropiperoides	Persicaria wallichii
	water pepper, swamp smartweed	garden knotweed, Himalayan knotweed
Habit	Herbaceous perennial, up to 1 m. tall, usually decumbent and tending to root freely.	Vigorous, rhizomatous perennial with numerous, erect, reddish-brown, leafy, branching stems 1.5-2 m. tall.
Leaves	Leaves numerous on short petioles, alternate, scarcely reduced upward, lanceolate to oblong-lanceolate with an acute base, 5-12 cm. long; sheathing stipules 1-2 cm. long with bristly hairs around the top.	Leaves alternate, the lower petiolate, becoming subsessile upward; leaf blade oblong-lanceolate to ovate-lanceolate, acuminate, up to 20 cm. long, the base truncate to cordate; stipules sheathing, not lacerate.
Flowers	Inflorescence of 2 or more spike-like, interrupted racemes; perianth greenish to white or pinkish, 2.5-3 mm. long, 5-lobed half the length, the segments oblong and sub-equal; stamens 8 with short filaments	Inflorescence an open, terminal panicle; flowers white, perfect; the 5 perianth segments obovate, 3-4 mm. long, not keeled.
Fruits	Achene with three sharp angles, black, smooth and shining, about 3 mm. long.

	Persicaria hydropiperoides	Persicaria wallichii
Identification notes		Achene 3-angled, black, smooth and shining, 3 mm. long.
Flowering time	July-September	July-October
Habitat	Moist to swampy areas, often growing in mud, from the lowlands to the lower mountain valleys.	Waste areas, roadsides, and other disturbed areas where often where somewhat moist.
Distribution	Occurring chiefly west of the Cascades crest in Washington; British Columbia to Mexico and South America, east across North America to the Atlantic coast. [WildflowerSearch map] [BONAP county map]	Occurring west of the Cascades crest in Washington; British Columbia to California; also in eastern North America. [WildflowerSearch map] [BONAP county map]
Origin	Native	Introduced from eastern Asia
Conservation status	Not of concern	Not of concern
Sibling taxa	P. amphibia, P. hydropiper, P. lapathifolia, P. maculosa, P. punctata, P. wallichii	P. amphibia, P. hydropiper, P. hydropiperoides, P. lapathifolia, P. maculosa, P. punctata
Subordinate taxa		P. wallichii var. wallichii
Web links	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	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

Persicaria wallichii

water pepper, swamp smartweed

garden knotweed, Himalayan knotweed

Habit

Herbaceous perennial, up to 1 m. tall, usually decumbent and tending to root freely.

Vigorous, rhizomatous perennial with numerous, erect, reddish-brown, leafy, branching stems 1.5-2 m. tall.

Leaves

Leaves numerous on short petioles, alternate, scarcely reduced upward, lanceolate to oblong-lanceolate with an acute base, 5-12 cm. long; sheathing stipules 1-2 cm. long with bristly hairs around the top.

Leaves alternate, the lower petiolate, becoming subsessile upward;

leaf blade oblong-lanceolate to ovate-lanceolate, acuminate, up to 20 cm. long, the base truncate to cordate;

stipules sheathing, not lacerate.

Flowers

Inflorescence of 2 or more spike-like, interrupted racemes;

perianth greenish to white or pinkish, 2.5-3 mm. long, 5-lobed half the length, the segments oblong and sub-equal;

stamens 8 with short filaments

Inflorescence an open, terminal panicle;

flowers white, perfect; the 5 perianth segments obovate, 3-4 mm. long, not keeled.

Fruits

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

Persicaria hydropiperoides

Persicaria wallichii

Identification notes

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

Flowering time

July-September

July-October

Habitat

Moist to swampy areas, often growing in mud, from the lowlands to the lower mountain valleys.

Waste areas, roadsides, and other disturbed areas where often where somewhat moist.

Distribution

Occurring chiefly west of the Cascades crest in Washington; British Columbia to Mexico and South America, east across North America to the Atlantic coast.

[WildflowerSearch map]

[BONAP county map]