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

Engelmann's knotweed

Habit Herbs. Herbs.
Stems

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

erect, green or purplish brown, branched from base, not wiry, 4–30 cm, glabrous or minutely papillose-scabridulous.

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 persistent, distal leaves abruptly reduced to bracts;

ocrea 3–5 mm, papillose-scabridulous or glabrous, proximal part funnelform, distal part becoming lacerate with age;

petiole 0.1–2 mm;

blade 1-veined, not pleated, linear-oblanceolate, 10–20(–25) × 1–3(–4) mm, margins revolute, smooth, apex acute to mucronate.

Inflorescences

axillary;

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

axillary and terminal, spikelike, loosely floriferous nearly to base, elongate;

cymes spaced along branches, (1–)2–4-flowered.

Pedicels

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

exserted from ocreae, reflexed, 1–3 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.

closed;

perianth 1.5–2(–2.5) mm;

tube 18–26% of perianth length;

tepals initially overlapping and cucullate, later forced apart by developing achene, greenish or sometimes purple, with white margins, petaloid or sepaloid, oblong, ± flat or navicular, apex rounded;

midveins unbranched;

stamens 5–8.

Achenes

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

exserted from perianth, black, elliptic, 1.2–2.3 mm, faces subequal, shiny, smooth.

Polygonum minimum

Polygonum engelmannii

Phenology Flowering Jul–Sep. Flowering Jun–Sep.
Habitat Alpine to subalpine sites, open or semibarren soil Dry to moist sandy or well-drained soils, sagebrush desert to lower mountains
Elevation 1500-3300 m (4900-10800 ft) 1000-1500 m (3300-4900 ft)
Distribution
from FNA
AK; CA; CO; ID; MT; NV; OR; UT; WA; WY; AB; BC
[WildflowerSearch map]
[BONAP county map]
from FNA
CO; ID; MT; NV; SD; UT; WY; AB; BC
[BONAP county map]
Source FNA vol. 5, p. 569. FNA vol. 5, p. 569.
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. 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. torreyi P. douglasii subsp. engelmannii
Name authority S. Watson: Botany (Fortieth Parallel), 315. (1871) Greene: Bull. Calif. Acad. Sci. 1: 126. (1885)
Web links