The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

Persian knotweed, silver sheath knotweed

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

Habit Plants green, heterophyllous. Herbs, compact, often cushion-like.
Stems

erect or decumbent, branched mostly from base, not wiry, 15–100 cm.

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

Leaves

ocrea 4–8 mm, proximal part cylindric, distal part soon disintegrating into curly or straight fibers;

petiole 0–1.5 mm;

blade bluish green, lanceolate or linear-lanceolate, 15–50 × 2–8 mm, margins flat, apex acute;

stem leaves 2.1–4 times as long as branch leaves;

distal leaves abruptly reduced and not overtopping flowers (shorter than or equaling flowers).

± 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.

Inflorescence(s)

axillary and terminal, spikelike;

cymes aggregated at tips of stems and branches, 4–6-flowered, bracts inconspicuous.

axillary;

cymes in most axils, 1-flowered.

Pedicels

enclosed in ocreae, 1–2 mm.

absent.

Flowers

closed;

perianth 1.8–2.4 mm;

tube 10–22% of perianth length;

tepals overlapping, green or white, usually with pink, rarely red or white, margins, petaloid, not keeled, oblong to obovate, cucullate;

midveins usually unbranched;

stamens 7–8.

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.

Achenes

enclosed in perianth, brown, ovate, 3-gonous, 1.3–2.3 mm, faces subequal, slightly concave, apex not beaked, with concave edges, shiny, smooth; late-season achenes unknown.

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

Polygonum argyrocoleon

Polygonum parryi

Phenology Flowering May–Oct. Flowering May–July.
Habitat Fields, gardens, disturbed sites, often in saline soils Vernally moist, open, sandy or rocky places
Elevation 0-1200 m (0-3900 ft) 500-2000 m (1600-6600 ft)
Distribution
from FNA
AZ; CA; CO; FL; ID; LA; MA; MO; NC; NM; NV; TX; UT; VT; WV; c Asia [Introduced in North America]
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; WA
[WildflowerSearch map]
[BONAP county map]
Source FNA vol. 5, p. 560. FNA vol. 5, p. 563.
Parent taxa Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia
Sibling taxa
P. achoreum, 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. parryi, 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. oxyspermum, P. paronychia, P. patulum, P. plebeium, P. polygaloides, P. ramosissimum, P. sawatchense, P. shastense, P. spergulariiforme, P. striatulum, P. tenue, P. utahense
Name authority Steudel ex Kunze: Linnaea 20: 17. (1847) Greene: Bull. Torrey Bot. Club 8: 99. (1881)
Web links