Flora of North America species comparison

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Polygonum nuttallii

Nuttall's knotweed
Habit Herbs.
Stems

spreading to erect, sometimes zigzagged, purplish, simple or branched, wiry, (5–)10–35 cm, papillose-scabridulous.
Leaves

evenly distributed or crowded at branch tips, articulated to ocreae, basal leaves persistent, distal leaves gradually reduced to bracts;

ocrea 3–4 mm, papillose-scabridulous, proximal part funnelform, distal part finely lacerate;

petiole 0.1–2 mm;

blade 1-veined, not pleated, linear to narrowly oblong-elliptic, 8–30 × 1–4(–7) mm, margins narrowly revolute, never touching along midrib, smooth, apex acute, mucronate, ± glaucous adaxially.
Inflorescences

axillary and terminal, spikelike, dense;

cymes mostly congested toward tips of branches, 2–3-flowered.
Pedicels

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

semi-open or closed;

perianth 1.8–2.4 mm;

tube 25–33% of perianth length;

tepals overlapping, greenish, white, or pink with pink margins, petaloid, oblong, cucullate, navicular in distal 1/4, apex rounded;

midveins unbranched;

stamens 8.
Achenes

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

Polygonum nuttallii
Phenology Flowering May–Oct.
Habitat Dry prairies, open knolls in lower mountains, open sites in lowland and montane zones, sandy soil
Elevation 800-1100 m (2600-3600 ft)
Distribution
from FNA
OR; WA; BC
[WildflowerSearch map]
[BONAP county map]
Discussion

C. L. Hitchcock (1964) suggested that Polygonum nuttallii is but a small-flowered form of P. spergulariiforme. Although morphologically similar, P. nuttallii differs from P. spergulariiforme in some respects, including its wiry, purplish stems, short and funnelform ocreae, adaxially glaucous leaves, longer bracts, shorter fruiting perianth, and achenes.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 5, p. 570.
Parent taxa 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. 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. intermedium, P. douglasii subsp. nuttallii
Name authority Small: Mongr. Amer. Sp. Polygonum, 132, plate 53. (1895)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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