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Parry's knotweed, Parry's or prickly knotweed, prickly knotweed

knotweed, sharp-fruit knotweed

Habit Herbs, compact, often cushion-like. Plants green to blue-green, homophyllous.
Stems

erect, green-brown, simple or branched from base, not wiry, 2–5(–8) cm, glabrous.

prostrate to ascending, branched at proximal and middle nodes, not wiry, 20–100 cm.

Leaves

± uniformly distributed, dense, not articulated to ocreae, basal leaves ± persistent, distal leaves gradually reduced to bracts;

ocrea 2–4(–5) mm, glabrous, proximal part cylindric, distal part deeply lacerate, disintegrating into white, curled fibers;

petiole absent;

blade 3-veined, without pleats, linear-lanceolate, subulate, 5–13(–20) × 0.4–1 mm, margins revolute, smooth, apex spine-tipped.

ocrea 6.5–12 mm, proximal part cylindric, pruinose, distal part hyaline, soon disintegrating into brown fibers or nearly completely deciduous;

petiole 0–1 mm;

blade green to bluish green, elliptic-lanceolate to linear, 10–35 × 1.5–15 mm, margins flat or narrowly revolute, apex acute;

middle stem leaves slightly larger than adjacent branch leaves, distal leaves overtopping flowers.

Inflorescences

axillary;

cymes in most axils, 1-flowered.

axillary, cymes uniformly distributed, 2–7-flowered.

Pedicels

absent.

exserted from ocreae, 2.5–5(–7) mm.

Flowers

closed;

perianth 1.5–2(–2.5) mm;

tube 6–15% of perianth length;

tepals overlapping, usually reddish with white margins, petaloid, oblong, navicular, apex acute;

midveins unbranched;

stamens 8.

semi-open;

perianth 3.5–5.5 mm;

tube 28–39% of perianth length;

tepals slightly overlapping, green, margins white to pink, petaloid, not keeled, oblong to obovate, not cucullate;

veins branched;

stamens 8.

Achenes

slightly exserted from perianth at maturity, dark brown, ovate, 1.2–1.6(–2) mm, faces subequal, shiny, smooth.

exserted from perianth, pale brown to dark brown, ovate, 3-gonous, (3.5–)4.1–5.5(–6.5) mm, faces subequal, apex not beaked, edges straight, shiny, smooth or with fine tubercles especially toward apex; late-season achenes unknown.

Polygonum parryi

Polygonum oxyspermum

Phenology Flowering May–July.
Habitat Vernally moist, open, sandy or rocky places
Elevation 500-2000 m (1600-6600 ft)
Distribution
from FNA
CA; WA
[WildflowerSearch map]
[BONAP county map]
from FNA
ME; NB; NF; NS; PE; QC; Europe
[BONAP county map]
Discussion

Subspecies 3 (2 in the flora).

The treatment by D. A. Webb and A. O. Chater (1963) of the Polygonum oxyspermum complex is followed here. T. Karlsson (2000) accepted P. raii and P. oxyspermum as distinct species.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Ocreae with prominent veins, distal part disintegrating, veins persistent; leaf blades 5-8 times as long as wide; achenes 4.1-5.5(-6.5) mm, exserted 1-2.5 mm from perianth
subsp. oxyspermum
1. Ocreae without prominent veins, distal part disintegrating, nearly completely deciduous; leaf blades 3.5-5 times as long as wide; achene (3.5-)4-5 mm, exserted 0.5-1.3(-1.8) mm from perianth
subsp. raii
Source FNA vol. 5, p. 563. FNA vol. 5, p. 554.
Parent taxa Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum
Sibling taxa
P. achoreum, P. argyrocoleon, P. austiniae, P. aviculare, P. bidwelliae, P. bolanderi, P. californicum, P. cascadense, P. douglasii, P. engelmannii, P. erectum, P. fowleri, P. glaucum, P. heterosepalum, P. hickmanii, P. humifusum, P. majus, P. marinense, P. minimum, P. nuttallii, P. oxyspermum, P. paronychia, P. patulum, P. plebeium, P. polygaloides, P. ramosissimum, P. sawatchense, P. shastense, P. spergulariiforme, P. striatulum, P. tenue, P. utahense
P. achoreum, P. argyrocoleon, P. austiniae, P. aviculare, P. bidwelliae, P. bolanderi, P. californicum, P. cascadense, P. douglasii, P. engelmannii, P. erectum, P. fowleri, P. glaucum, P. heterosepalum, P. hickmanii, P. humifusum, P. majus, P. marinense, P. minimum, P. nuttallii, P. paronychia, P. parryi, P. patulum, P. plebeium, P. polygaloides, P. ramosissimum, P. sawatchense, P. shastense, P. spergulariiforme, P. striatulum, P. tenue, P. utahense
Subordinate taxa
P. oxyspermum subsp. oxyspermum, P. oxyspermum subsp. raii
Name authority Greene: Bull. Torrey Bot. Club 8: 99. (1881) C. A. Meyer & Bunge ex Ledebour: Index Seminum (Dorpat) 1824: 5. (1824)
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