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

Douglas' knotweed, renouée de Douglas

Habit Herbs, compact, often cushion-like. Herbs.
Stems

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

erect, green, simple or branched, not wiry, 5–80 cm, glabrous or sparsely papillose-scabridulous.

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.

uniformly distributed, articulated to ocreae, basal leaves caducous, distal leaves abruptly reduced to bracts;

ocrea 6–12 mm, glabrous or minutely papillose-scabridulous, proximal part cylindric, distal part hyaline, lacerate;

petiole 0.1–2 mm;

blade 1-veined, not pleated, linear, narrow-oblong, or oblanceolate, 15–55 × 2–8(–12) mm, margins revolute, smooth or papillose-denticulate;

apex acute to mucronate.

Inflorescences

axillary;

cymes in most axils, 1-flowered.

axillary and terminal, spikelike, elongate;

cymes widely spaced along branches, 2–4-flowered.

Pedicels

absent.

mostly exserted from ocreae, reflexed, 2–6 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.

closed;

perianth 3–4.5 mm;

tube 20–28% of perianth length;

tepals overlapping, green to tannish with white or pink margins, petaloid, oblong, cucullate, navicular, apex rounded;

midveins usually branched, rarely unbranched;

stamens 8.

Achenes

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

enclosed in perianth, black, elliptic or oblong to ovate, 3–4(–4.5) mm, faces subequal, shiny or dull, smooth or minutely striate-tubercled.

Polygonum parryi

Polygonum douglasii

Phenology Flowering May–July. Flowering Jun–Oct.
Habitat Vernally moist, open, sandy or rocky places Dry, often disturbed places, rock outcrops, sandy ground
Elevation 500-2000 m (1600-6600 ft) 300-3000 m (1000-9800 ft)
Distribution
from FNA
CA; WA
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; CA; CO; IA; ID; MI; MN; MT; NE; NH; NM; NV; NY; OR; SD; UT; VA; VT; WA; WY; AB; BC; MB; ON; QC; SK; YT
[WildflowerSearch map]
[BONAP county map]
Discussion

Five taxa that have been included in Polygonum douglasii (E. Murray 1982; J. C. Hickman 1984; J. T. Kartesz and K. N. Gandhi 1990) are treated here as distinct species: P. austiniae, P. majus, P. nuttallii, P. sawatchense, and P. spergulariiforme. Hickman noted extensive intergradation and numerous intermediate specimens among those sympatric elements, but qualitative or quantitative characters allow reliable discrimination in most cases (M. Costea and F. J. Tardif 2005), and species are here circumscribed similar to C. L. Hitchcock (1964).

Greene described var. latifolium as having leaf blades and achenes broader than those of var. douglasii. C. L. Hitchcock (1964) recognized the former, but the characters used to distinguish it appear to vary continuously, and reliable separation is not possible.

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

Source FNA vol. 5, p. 563. FNA vol. 5, p. 567.
Parent taxa Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia
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. 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. parryi, P. patulum, P. plebeium, P. polygaloides, P. ramosissimum, P. sawatchense, P. shastense, P. spergulariiforme, P. striatulum, P. tenue, P. utahense
Synonyms P. douglasii var. latifolium, P. emaciatum, P. montanum, P. tenue var. commune, P. tenue var. latifolium
Name authority Greene: Bull. Torrey Bot. Club 8: 99. (1881) Greene: Bull. Calif. Acad. Sci. 1: 125. (1885)
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