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broad-leaf knotweed, broad-leaf or leafy dwarf knotweed, leafy dwarf knotweed, little mountain knotweed, zigzag knotweed

Shasta knotweed

Habit Herbs. Subshrubs.
Stems

prostrate to erect, often zigzagged, reddish brown, simple or branched from base, wiry, 2–30 cm, papillose-scabrid-ulous.

prostrate to ascending, brown, branched, gnarled, not wiry, 5–40 cm, glabrous.

Leaves

evenly distributed or crowded at branch tips, articulated to ocreae, basal leaves persistent, hardly reduced distally;

ocrea 1–4 mm, papillose-scabridulous, proximal part cylindric, distal part entire or dentate-lacerate;

petiole 0.1–3 mm;

blade 1-veined, not pleated, narrowly elliptic, elliptic, ovate, obovate, or subround, 6–27 × 3–8 mm, margins flat, smooth, irregularly thickened or papillose-denticulate, apex apiculate, green adaxially.

± uniformly distributed, articulated to ocreae, basal leaves caducous or persistent, distal leaves not reduced in size;

ocrea 3–5 mm, glabrous, proximal part cylindric, distal part membranous, deciduous with leaves;

petiole 0–0.5 mm;

blade 1-veined, without pleats, lanceolate to elliptic, 5–25 × 2–5 mm, coriaceous, margins revolute, smooth, apex acute.

Inflorescences

axillary;

cymes from near stem and branch bases, sometimes also crowded at branch apices, 1–3-flowered.

axillary;

cymes in distal axils, 2–6-flowered.

Pedicels

enclosed in ocreae, erect to spreading, 2–3 mm.

enclosed in or slightly exserted from ocreae, erect, 2–4 mm.

Flowers

semi-open or closed;

perianth 1.8–2.5 mm;

tube 22–29% of perianth length;

tepals overlapping, greenish with narrow white or pink margins, almost sepaloid, oblong, cucullate, ± navicular, apex rounded;

midveins thickened, unbranched;

stamens 8.

open or semi-open;

perianth 5–9 mm;

tube 7–15% of perianth length, tepals partially overlapping, uniformly pink or white, petaloid, ovate to ovate-round, apex rounded;

midveins with numerous branched lateral veins;

stamens 8.

Achenes

enclosed in perianth or tip exserted, black, elliptic to ovate, 1.8–2.3 mm, faces subequal, smooth, shiny.

enclosed in or slightly exserted from perianth, brown, narrowly ovate, 3–4 mm, faces subequal, shiny, smooth.

Polygonum minimum

Polygonum shastense

Phenology Flowering Jul–Sep. Flowering Jul–Sep.
Habitat Alpine to subalpine sites, open or semibarren soil Rocky or gravelly slopes
Elevation 1500-3300 m (4900-10800 ft) 2100-3400 m (6900-11200 ft)
Distribution
from FNA
AK; CA; CO; ID; MT; NV; OR; UT; WA; WY; AB; BC
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; NV; OR
[WildflowerSearch map]
[BONAP county map]
Discussion

Polygonum shastense may be cultivated in rock gardens in rock crevices with favorable water regime and shaded in summer.

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

Source FNA vol. 5, p. 569. FNA vol. 5, p. 563.
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. 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. parryi, P. patulum, P. plebeium, P. polygaloides, P. ramosissimum, P. sawatchense, P. spergulariiforme, P. striatulum, P. tenue, P. utahense
Synonyms P. torreyi
Name authority S. Watson: Botany (Fortieth Parallel), 315. (1871) W. H. Brewer: Proc. Amer. Acad. Arts 8: 400. (1872)
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