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California knotweed

pleat-leaf knotweed, slender knotweed

Habit Herbs. Herbs.
Stems

erect, green, simple or divaricately branched, ± wiry, 4–40 cm, papillose-scabridulous.

erect, green or brown-ish, simple or branched from below middle, not wiry, 5–50 cm, glabrous or papillose-scabridulous.

Leaves

uniformly distributed, not articulated to ocreae, basal leaves usually caducous, distal leaves abruptly reduced to bracts;

ocrea 5–10 mm, glabrous or papillose-scabridulous, proximal part cylindric, distal part white or tawny, disintegrating into ± bristly-fringed fibers;

petiole absent;

blade 3-veined, without pleats, linear, 5–25(–30) × 0.5–2 mm, margins revolute, papillose-denticulate or smooth, apex mucronate or weakly spine-tipped.

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

ocrea 6–15 mm, glabrous or papillose-scabridulous, proximal part cylindric, distal part soon disintegrating into a few brown fibers;

petiole 0.1–1 mm;

blade 1-veined, with 1 pleat on each side of midrib, narrowly lanceolate to linear, 25–40 × 1–8 mm, margins usually flat, papillose-denticulate, apex mucronate or cuspidate.

Inflorescences

axillary;

cymes in distal axils, 1-flowered.

axillary and terminal, spikelike, slender, elongate;

cymes spaced along branches, 1–2(–3)-flowered.

Pedicels

absent.

enclosed in ocreae, erect, 1–1.5 mm.

Flowers

open or closed;

perianth 2.5–3.5 mm;

tube 10–20% of perianth length;

tepals overlapping, uniformly white to pink, petaloid, elliptic, navicular, apex acute to acuminate;

midveins unbranched;

stamens 8.

closed;

perianth 2.5–4.2 mm;

tube 15–22% of perianth length;

tepals overlapping, green, often brownish when dried, with pink or white margins, petaloid or sepaloid, elliptic, cucullate, navicular, apex rounded;

midveins usually unbranched, rarely branched;

stamens 8.

Achenes

enclosed in or slightly exserted from perianth, brown, narrowly elliptic, 1.8–2.2 mm, faces subequal, shiny, smooth.

enclosed in or slightly exserted from perianth, black, elliptic to oblong, 2.3–4 mm, faces subequal, shiny, smooth or minutely striate-tubercled near edges and apex.

2n

= 20.

Polygonum californicum

Polygonum tenue

Phenology Flowering May–Sep. Flowering Jun–Oct.
Habitat Open places, including serpentine Dry acid soils in exposed sites
Elevation 40-1200 m (100-3900 ft) 100-1000 m (300-3300 ft)
Distribution
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; CT; DC; DE; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; NC; NE; NH; NJ; NY; OH; OK; PA; RI; SD; TN; TX; VA; VT; WI; WV; WY; ON
[WildflowerSearch map]
[BONAP county map]
Source FNA vol. 5, p. 564. 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. 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. parryi, P. patulum, P. plebeium, P. polygaloides, P. ramosissimum, P. sawatchense, P. shastense, P. spergulariiforme, P. striatulum, P. utahense
Synonyms Duravia californica, P. greenei P. tenue var. protrusum
Name authority Meisner: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 14: 100. (1856) Michaux: Fl. Bor.-Amer. 1: 238. (1803)
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