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arrow-leaf knotweed, arrow-leaf tearthumb, arrow-vine, renouée sagittée

pink smartweed

Habit Plants annual, 3–20 dm; roots also often arising from proximal nodes. Plants annual, 2–18 dm; roots also rarely arising from basal nodes; rhizomes and stolons absent.
Stems

scandent, ribbed, glabrous;

prickles 1–1.5 mm.

ascending to erect, rarely decumbent, branched, ribbed, glabrous or appressed-pubescent to spreading-pubescent distally, stipitate-glandular or, rarely, without stipitate-glands.

Leaves

ocrea brownish, cylindric, (3–)5–13 mm, chartaceous, base inflated or not, without prickles, margins oblique, glabrous or ciliate at tip with bristles 0.2–1 mm, surface glabrous;

petiole 0.5–4 cm;

blade broadly lanceolate to oblong, 2–8.5 × 1–3 cm, base sagittate to cordate, margins entire, ciliate or eciliate, apex obtuse to acute, faces glabrous or densely appressed-pubescent, usually with retrorse prickles along midvein abaxially.

ocrea brownish, cylindric, 6–20 mm, chartaceous, base inflated, margins truncate, eciliate or ciliate with bristles to 1 mm, surface glabrous or scabrous proximally, eglandular;

petiole 0.1–1.5(–2.3) cm, glabrous or appressed-pubescent;

blade sometimes with dark triangular or lunate blotch adaxially, linear-lanceolate to ovate-lanceolate, 2.3–13(–18) × (0.4–)1–2.3 cm, base tapered to cuneate, margins antrorsely scabrous, apex acute to acuminate, faces glabrous or appressed-pubescent along midveins, glandular-punctate abaxially.

Inflorescences

capitate or paniclelike, uninterrupted, 5–15 × 4–10 mm;

peduncle 10–80 mm, usually glabrous, sometimes with retrorse prickles proximally;

ocreolae overlapping, margins eciliate.

terminal and axillary, erect, uninterrupted, 8–60 × 10–18 mm;

peduncle 8–60(–70) mm, glabrous or pubescent, usually stipitate-glandular;

ocreolae overlapping, margins eciliate or ciliate with bristles to 0.8 mm.

Pedicels

mostly ascending, 1–1.5 mm.

ascending, 1.5–5 mm.

Flowers

2–3 per ocreate fascicle;

perianth white or greenish white, often tinged pink or red, sometimes entirely pink, glabrous, accrescent, not becoming blue and fleshy in fruit;

tepals 5, connate 1/3–1/2 their length, broadly elliptic, 3–5 mm, apex obtuse;

stamens 8, filaments distinct, free;

anthers pink, ovate;

styles 3, connate to middle.

2–11 per ocreate fascicle, heterostylous;

perianth pink, glabrous, not glandular-punctate, accrescent;

tepals 5, connate ca. 1/4–1/3 their length, obovate to elliptic, 3–4.6 mm, veins prominent, not anchor-shaped, margins entire, apex obtuse to rounded;

stamens 6–8, included or exserted;

anthers pink or red, elliptic;

styles 2(–3), included or exserted, connate at bases.

Achenes

included or styles exserted, light or dark brown to black, 3-gonous, 2.5–4 × 1.8–2.5 mm, dull to shiny, smooth to minutely punctate.

included or apex exserted, brownish black to black, discoid or, rarely, 3-gonous, 1 side usually slightly concave and other with central hump, (2–)2.2–2.9 × 2–2.8(–3) mm, shiny, smooth.

2n

= 40.

Persicaria sagittata

Persicaria bicornis

Phenology Flowering Jun–Oct. Flowering Jun–Oct.
Habitat Moist shaded sites, meadows, pastures, fens, swamps, shorelines of ponds and streams Moist, disturbed places, permanent and ephemeral wetlands, ditches, cultivated fields, shorelines of ponds and reservoirs
Elevation 0-1000 m (0-3300 ft) 50-1600 m (200-5200 ft)
Distribution
from FNA
AL; AR; CO; CT; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; ND; NE; NH; NJ; NY; OH; OK; PA; RI; SC; SD; TN; TX; VA; VT; WI; WV; MB; NB; NF; NS; ON; PE; QC; e Asia
[WildflowerSearch map]
[BONAP county map]
from FNA
AR; CO; IA; IL; KS; LA; MO; NE; NM; OK; SD; TX; WY
[WildflowerSearch map]
[BONAP county map]
Discussion

Persicaria sagittata is an extremely variable species. Achene and leaf characters have been used by some authors to separate North American and Asian populations, but these characters show weak geographic variation (C. W. Park 1988).

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

Persicaria bicornis is a characteristic smartweed of permanent and ephemeral wetlands and moist, disturbed sites in the Great Plains. It often has been included in P. pensylvanica but can be distinguished readily by its heterostylous flowers. The achenes, which usually bear an obscure or prominent hump in the center of one face, also are diagnostic. This hump often ruptures the side of the perianth on fruiting herbarium specimens. Persicaria bicornis also has leaf blades that are on average narrower than are those of P. pensylvanica, and populations exhibit less variation in perianth color. As in P. pensylvanica, flowers with three styles and trigonous achenes are produced very rarely.

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

Source FNA vol. 5, p. 577. FNA vol. 5, p. 589.
Parent taxa Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Echinocaulon Polygonaceae > subfam. Polygonoideae > Persicaria > sect. Persicaria
Sibling taxa
P. amphibia, P. arifolia, P. bicornis, P. bungeana, P. capitata, P. careyi, P. chinensis, P. glabra, P. hirsuta, P. hydropiper, P. hydropiperoides, P. lapathifolia, P. longiseta, P. maculosa, P. meisneriana, P. minor, P. nepalensis, P. orientalis, P. pensylvanica, P. perfoliata, P. punctata, P. robustior, P. setacea, P. virginiana, P. wallichii
P. amphibia, P. arifolia, P. bungeana, P. capitata, P. careyi, P. chinensis, P. glabra, P. hirsuta, P. hydropiper, P. hydropiperoides, P. lapathifolia, P. longiseta, P. maculosa, P. meisneriana, P. minor, P. nepalensis, P. orientalis, P. pensylvanica, P. perfoliata, P. punctata, P. robustior, P. sagittata, P. setacea, P. virginiana, P. wallichii
Synonyms Polygonum sagittatum, Polygonum sagittatum var. gracilentum, Tracaulon sagittatum, Truellum sagittatum Polygonum bicorne, P. longistyla, Polygonum longistylum
Name authority (Linnaeus) H. Gross: Beih. Bot. Centralbl. 37(2): 113. (1919) (Rafinesque) Nieuwland: Amer. Midl. Naturalist 3: 201. (1914)
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