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black bindweed, climbing bindweed, climbing knotweed, Eurasian black bindweed, ivy bindweed

knotweed

Habit Herbs, annual, not rhizomatous, 0.5–1 m. Trees, shrubs, vines, or herbs, perennial or annual, homophyllous (heretophyllous in some species of Polygonum); root fibrous or a solid taproot, rarely tuberous.
Stems

scandent or sprawling, branched proximally, herbaceous, puberulent, sometimes mealy, not glaucous.

usually prostrate to erect, sometimes scandent, not scapose, rarely with recurved spines (some species of Persicaria), glabrous or pubescent, sometimes glandular;

nodes usually swollen;

branches free (adnate to stems distal to nodes and appearing to arise internodally in Polygonella);

tendrils absent (except in Antigonon and Brunnichia).

Leaves

ocrea persistent or deciduous, tan or greenish brown, cylindric, 2–4 mm, margins oblique, face not fringed with reflexed hairs and slender bristles at base, otherwise glabrous or scabrid;

petiole 0.5–5 cm, puberulent in lines;

blade cordate-ovate, cordate-hastate, or sagittate, 2–6(–15) × 2–5(–10) cm, base cordate, margins wavy, scabrid, apex acuminate, abaxial face usually mealy and, rarely, minutely dotted, not glaucous, adaxial face glabrous.

deciduous (persistent in Coccoloba and sometimes more than 1 year in Antigonon and Polygonella), basal or basal and cauline, rarely cauline only, mostly alternate;

ocrea present, persistent or deciduous, cylindric to funnelform, chartaceous, membranous, coriaceous, or, rarely, foliaceous or partly so;

petiole present or absent, rarely articulate basally (Fagopyrum, Fallopia, Polygonella, Polygonum), rarely with extrafloral nectaries (Fallopia, Muehlenbeckia);

blade simple with entire margins, rarely undulate or lobed.

Inflorescences

axillary, erect or spreading, spikelike, 2–10(–15) cm, axes puberulent;

peduncle 0.1–10 cm or absent, glabrous or scabrid distally in lines.

terminal or terminal and axillary, spikelike, racemelike, paniclelike, cymelike, or, rarely, capitate, comprising simple or branched clusters of compound inflorescences;

bracts absent;

peduncle spreading to erect, sometimes absent;

clusters of flowers subtended by connate bracteoles forming persistent membranous tube (ocreola), awnless.

Pedicels

ascending or spreading, articulated distally, 1–3 mm, glabrous or, rarely, scabrid.

Flowers

bisexual, 3–6 per ocreate fascicle;

perianth nonaccrescent, greenish white, often with pinkish or purplish base, 3–5 mm including stipelike base, glabrous or outer 3 with blunt, hyaline hairs;

tepals elliptic to obovate, apex obtuse to acute, outer 3 obscurely keeled;

stamens 8;

filaments flattened proximally, glabrous;

styles connate distally;

stigmas capitate.

usually bisexual, sometimes bisexual and unisexual on same plant, rarely unisexual only, 1–20+ per ocreate fascicle, often with stipelike base distal to articulation;

perianth often accrescent in fruit, often greenish, white, pink, yellow, red, or purple, usually unwinged and unkeeled (winged or, sometimes, keeled in Fallopia, rarely keeled in Polygonum), campanulate or urceolate, sometimes membranous, indurate, or fleshy in fruit, rarely developing raised tubercles proximally (Rumex), glabrous or pubescent, sometimes glandular or glandular-punctate;

tepals 2–6, usually in 2 whorls, distinct or connate proximally and forming tube, petaloid or sepaloid, monomorphic or dimorphic;

nectary a disk at base of ovary or glands associated with bases of filaments;

stamens usually (1–)6–9, staminodes rarely present;

filaments distinct, or connate basally and sometimes forming staminal tube, free or adnate to perianth tube;

pistils (2–)3(–4)-carpellate;

ovary 1-locular (sometimes with vestigial partitions proximally);

ovule 1, orthotropous or, rarely, anatropous, placentation basal or free-central;

styles 1–3, erect to spreading or recurved, distinct or connate proximally;

stigmas peltate, capitate, fimbriate, or penicillate.

Achenes

included, black, 4–5(–6) × 1.8–2.3 mm, dull, minutely granular-tuberculate, especially on faces; fruiting perianth glabrous or with blunt, hyaline hairs, wings absent or, rarely, flat to undulate, 0.4–0.9 mm wide at maturity, scarcely decurrent on stipelike base, margins entire.

yellowish, brown, red, or black, homocarpic (sometimes heterocarpic in Polygonum), winged or unwinged, usually 2–3-gonous, sometimes discoid, biconvex, or spheroidal, rarely 4-gonous.

Seeds

embryo usually straight or curved, rarely folded.

2n

= 40.

Fallopia convolvulus

Polygonaceae subfam. polygonoideae

Phenology Flowering May–Oct.
Habitat Cultivated ground, waste places
Elevation 0-2700 m (0-8900 ft)
Distribution
from FNA
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NL; NS; ON; PE; QC; SK; YT; SPM; Greenland; Eurasia [Introduced in North America; introduced in South America (Argentina, Chile), Africa (Algeria, Morocco, Republic of South Africa), Pacific Islands (Hawaii, New Zealand), Australia]
[WildflowerSearch map]
[BONAP county map]
Mainly temperate regions of North America
Discussion

Fallopia convolvulus can be an aggressive weed in crop fields. Rare plants with winged fruiting perianths have been named var. subalata; that characteristic often varies within populations.

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

Genera 28, species ca. 850 (16 genera, 160 species in the flora).

Morphological (K. Haraldson 1978; L.-P. Ronse Decraene and J. R. Akeroyd 1988; Ronse Decraene et al. 2000; Hong S. P. et al. 1998) and molecular (A. S. Lamb Frye and K. A. Kron 2003) data provide support for separation of Persicaria from Polygonum. Further studies are needed to elucidate the relationships of allied genera, particularly Aconogonon, Bistorta, and Koenigia with Persicaria, and Fallopia and Polygonella with Polygonum.

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

Key
1. Tendrils present; plants vines
→ 2
1. Tendrils absent; plants trees, shrubs, or herbs, rarely vinelike shrubs
→ 3
2. Perianths pink to purple or, rarely, white or yellow, membranous; pedicels not 3-winged
Antigonon
2. Perianths green to greenish yellow, indurate; pedicels 3-winged, 1 wing more prominent and becoming greatly expanded in fruit
Brunnichia
3. Plants trees or shrubs; tubes of pistillate flowers becoming fleshy in fruit
Coccoloba
3. Plants herbs, subshrubs, or, rarely, vinelike shrubs; tubes of pistillate flowers rarely becoming fleshy in fruit
→ 4
4. Tepals 6
→ 5
4. Tepals 3, 4, or 5
→ 7
5. Flowers unisexual; outer 3 tepals of pistillate flowers each with apex ending in stout spine
Emex
5. Flowers bisexual or, rarely, unisexual; outer 3 tepals each without apex ending in stout spine
→ 6
6. Achenes winged; inner tepals of fruiting perianths nonaccrescent; stamens (6-)9
Rheum
6. Achenes unwinged; inner tepals of fruiting perianths usually accrescent; stamens 6
Rumex
7. Herbs annual; tepals 3 [4]; stamens (1-)3[-5]
Koenigia
7. Herbs perennial or annual, or shrubs; tepals 4-5; stamens 3-8
→ 8
8. Tepals 4; achenes lenticular, winged; leaves mostly basal
Oxyria
8. Tepals 4 or 5; achenes 3-gonous, discoid, biconvex, spheroidal, or 4-gonous, unwinged or essentially so; leaves cauline or basal and cauline, rarely mostly basal
→ 9
9. Branches adnate to stems, appearing to arise internodally
Polygonella
9. Branches not adnate to stems, not appearing to arise internodally
→ 10
10. Plants shrubs, vinelike; flowers unisexual, tubes of pistillate flowers becoming fleshy in fruit
Muehlenbeckia
10. Plants herbs or, if shrubs, not vinelike; flowers bisexual or, rarely, unisexual, if unisexual then tubes of pistillate flowers not becoming fleshy
→ 11
11. Outer tepals winged or keeled
→ 12
11. Outer tepals unwinged and unkeeled
→ 13
12. Outer tepals winged (keeled in F. ciliondis and, usually, F. convolvulus); ocreae chartaceous, tan to brownish, glabrous or scabrous to variously pubescent, never 2-lobed distally
Fallopia
12. Outer tepals keeled; ocreae often hyaline, silvery, glabrous, 2-lobed distally
Polygonum
13. Leaves mostly basal, some cauline; inflorescences terminal, spikelike; stems simple
Bistorta
13. Leaves cauline; inflorescences terminal and axillary or axillary; stems usually branched, rarely simple
→ 14
14. Achenes strongly exserted; perianths nonaccrescent; tepals distinct
Fagopyrum
14. Achenes included or exserted; perianths accrescent or nonaccrescent; tepals connate to 2/3 their lengths. [15. Shifted to left margin.—Ed.]
→ 15
15. Ocreae often hyaline, silvery, glabrous, 2-lobed distally, often disintegrating into fibers or completely
Polygonum
15. Ocreae chartaceous, usually tan, brown, or reddish, rarely silvery, glabrous or scabrous to variously pubescent, never 2-lobed distally, often tearing with age
→ 16
16. Inflorescences spikelike, paniclelike, or capitate; tepals 4 or 15, connate 1/ 2/ 3 their length (less than 5 their length in P. wallichii); stamens 5-8
Persicaria
16. Inflorescences racemelike or paniclelike; tepals 5, connate ca. 1/ 4 their length; stamens 8
Aconogonon
Source FNA vol. 5, p. 545. FNA vol. 5, p. 479. Author: Craig C. Freeman.
Parent taxa Polygonaceae > subfam. Polygonoideae > Fallopia Polygonaceae
Sibling taxa
F. baldschuanica, F. cilinodis, F. dumetorum, F. japonica, F. sachalinensis, F. scandens, F. ×bohemica
Subordinate taxa
Aconogonon, Antigonon, Bistorta, Brunnichia, Coccoloba, Emex, Fagopyrum, Fallopia, Koenigia, Muehlenbeckia, Oxyria, Persicaria, Polygonella, Polygonum, Rheum, Rumex
Synonyms Polygonum convolvulus, Bilderdykia convolvulus, F. convolvulus var. subalata, Reynoutria convolvulus, Tiniaria convolvulus
Name authority (Linnaeus) Á. Löve: Taxon 29: 300. (1970) Eaton: Bot. Dict. ed. 4, 30. (1836)
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