Polygonum aviculare |
Polygonum majus |
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Palouse knotweed, wiry knotweed |
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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 annual, the stem strongly angled, simple or freely-branched, 1-3 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. |
Leaves alternate, numerous, gradually reduced upward, the lower leaves linear to oblong, sessile, 2-5 cm. long and 2-7 mm. wide, jointed at the base; stipules 10-15 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. |
Flowers mostly paired in open elongate racemes, in the axils of reduced bracts or the lowest in leaf axils, the pedicles slender, reflexed; the 5 perianth segments 4-5 mm. long, attached 1/5 their length, with a greenish midvein and white to pink margins, obtuse; stamens 8, anthers purple; styles 3, short. |
Fruits | Achene with 3 sharp angles, brownish, smooth. |
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Polygonum aviculare |
Polygonum majus |
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Identification notes | Achene 3-angled, 3.5-4 mm. long and ½ as wide, smooth, black and shining, tapered at each end. | |
Flowering time | May-October | May-August |
Habitat | Dry or slightly moist, disturbed soil, often where hard-packed. | Dry, often semi-barren, gravelly to heavy soil, sagebrush desert to lower mountains. |
Distribution | Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast.
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Occurring east of the Cascades crest in Washington; British Columbia south to California, east to the Rocky Mountains.
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Origin | Both native and introduced | Native |
Conservation status | Not of concern | Not of concern |
Sibling taxa | ||
Subordinate taxa | ||
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