POLYGONACEAE Buckwheat Family

1a. Inner three sepals enlarged and valve-like, the outer three sepals linear and often reflexed

Rumex L.

1b. All sepals alike, often petaloid

2a. Achene exserted or loosely embraced by the shriveling calyx; smooth annuals with hastate, cordate or deltoid leaves

Fagopyrum esculentum Moench

2b. Achene +/- included in closely appressed and enlarged calyx (some spp. with linear to linear- lanceolate leaves often produce late-season fruit that are slightly exserted from the calyx)

3a. Three outer perianth lobes +/- keeled to broadly winged, especially in fruit

4a. Stems stiffly erect, becoming woody but dying to ground in winter; stigmas fimbriate; perianth enlarging in fruit; plants mostly dioecious

Reynoutria Houtt.

4b. Stems twining or trailing; stigmas capitate or peltate; perianth usually not enlarging in fruit; plants not dioecious

Fallopia Adans.

3b. Three outer perianth lobes neither keeled nor winged, even in fruit

5a. Flowers few in axils of ordinary or reduced leaves; ocrea 2-lobed, becoming +/- lacerate; filaments, at least the innermost, dilated

Polygonum L.

5b. Flowers in terminal and often axillary spikes, racemes, panicles or heads; ocrea various, not 2- lobed; filaments slender

Persicaria (L.) Mill.

Fallopia L.

1a. Ocrea with ring of reflexed bristles below

F. cilinodis (Michx.) Holub

1b. Ocrea without ring of reflexed bristles below

2a. Fruiting perianth 4-5 mm long, scarcely winged, basal lobes of leaves +/- acute; annuals; achene striate-papillose, dull

F. convolvulus (L.) Á.Löve

2b. Fruiting perianth 7-15 mm long, broadly winged, basal lobes of leaves various; annual or perennial; achene smooth, lustrous

F. scandens (L.) Holub

Persicaria (L.) Mill

1a. Leaves sagittate, auriculate, cordate, hastate, rarely truncate at base; reclining forbs with recurved prickles or bristles on the stem

2a. Leaf blades triangular in outline; perianth 4-parted

P. arifolia (L.) Haraldson

2b. Leaf blades lanceolate to narrowly elliptic; perianth 5-parted

P. sagittata (L.) H.Gross

1b. Leaves cuneate to obtuse, rarely rounded at base; upright, prostrate or sprawling forbs

3a. Plants perennial with rhizomes or stolons

4a. Ocrea not ciliate at summit or cilia usually < 1 mm; leaves usually oval to ovate

P. amphibia (L.) Delarbre

4b. Ocrea ciliate at summit with cilia > 1 mm long; leaves lanceolate

P. punctata Small

3b. Plants tap-rooted annuals

5a. Ocrea summit without cilia or cilia < 1 mm long

6a. Perianth without recognizable vein pattern, segments 5

P. pensylvanica (L.) M.Gómez

6b. Perianth with conspicuous anchor-shaped veins; perianth segments 4 (rarely 5)

P. lapathifolia (L.) Delarbre

5b. Ocrea summit with cilia > 1 mm long

7a. Perianth glandular-dotted

8a. Achenes lustrous, smooth; axillary flowers mostly absent (inflorescence not interrupted with small leaves)

P. punctata Small

8b. Achenes dull, minutely striate-dotted; axillary flowers present and +/- enclosed in ocrea (inflorescence interrupted with small leaves)

P. hydropiper (L.) Delarbre

7b. Perianth not glandular-dotted

P. maculosa Gray

Persicaria amphibia (L.) Delarbre

See Reveal & Atha (2012).

1a. Plants palustrine, usually with emergent leafy stems; ocreae never with flared apices; aerial leaves petiolate with acuminate tips; inflorescence spikes terminal, usually 2 (unequal), > 4 cm long

P. a. var. emersa (Michx.) J.C.Hickman

1b. Plants aquatic, usually with floating stems and leaves; ocreae with flared apices (when stranded); aerial leaves (when present) nearly sessile with somewhat cordate bases and blunt apices; inflorescence spikes usually 1, < 4 cm long

P. a. var. stipulacea (N.Coleman) H.Hara

Polygonum L.

Costea et al. (2005) describe Polygonum aviculare as “a taxonomically controversial polyploid complex of selfing annuals”. They report three infraspecific taxa for PEI: ssp. aviculare, ssp. depressum (Meisn.) Arcang., and ssp. neglectum (Besser) Arcang. Consult Costea et al. (2005) for a key to these taxa.

1a. Outer 3 tepals flat or folded, of approximately equal width and length to the inner tepals and not or scarcely concealing them; plants usually of inland, non-saline habitats such as roadsides, sidewalks, and disturbed habitats

P. aviculare L.

1b. Outer 3 tepals cucullate, much wider and often longer the inner tepals, partially or completely concealing them; plants usually of brackish and saline habitats such as coastal marshes and dunes

2a. Leaf blades pale green to white-green, somewhat to strongly glaucous; tepals loosely ascending and not investing apical portion of achene

P. oxyspermum C.A.Mey. & Bunge

2b. Leaf blades green, blue-green, or yellow-green, sometimes tinged with red; tepals +/- erect and rather closely investing achene

3a. Leaves lanceolate, oblanceolate or linear, 5-12 times as long as wide; plants +/- erect; pedicels usually greater than 2.5 mm, mostly long-exserted from ocreae; early season achenes mostly 2.5-3.5 mm long

P. ramosissimum Michx.

3b. Leaves oblong, ovate or obovate, 2-4 times as long as wide; achenes broadly ovate, usually >3 mm long, to 2.5 mm broad; fruiting perianth mostly > 3 mm; plant mostly bluish green to glaucous or rarely reddish tinged

P. fowleri B.L.Rob.

Reynoutria Houtt.

The hybrid of the below two species (R. ×bohemica Chrtek & Chrtková) is in cultivation and may occur spontaneously as well. It was first collected for PEI and Atlantic Canada by Sean Blaney on the eastern edge of Summerside, along the TransCanada Trail, in July 2004.

1a. Leaves acute to obtuse at base; perianth white; inflorescence slender-panicled racemes

R. japonica Houtt.

1b. Leaves cordate to rounded at base; perianth greenish-white; inflorescence small axillary clusters

R. sacchalinensis Nakai

Rumex L.

1a. Basal leaves with basal lobes; leaves acid tasting; flowers unisexual

2a. Leaves hastate; sepals not greatly enlarged in fruit; flowering in early May

R. acetosella L.

2b. Leaves sagittate; sepals greatly enlarged in fruit; flowering in June

R. acetosa L.

1b. Basal leaves cuneate, truncate or cordate at base; leaves not acid tasting; flowers perfect

3a. Valves of fruit without enlarged tubercles (rarely with one poorly developed)

R. longifolius DC.

3b. Valves of fruit with at least one conspicuously enlarged tubercle

4a. Valve margin entire, toothed or undulate

5a. Ascending stems with axillary branches or leaf tufts; leaves linear-lanceolate, tapering to both ends; fruiting pedicels filiform, curved; valves triangular, 3-6 mm long, truncate at base

6a. Inner tepals with a broad tubercle, the tubercle more than half as wide and nearly as long as its associated inner tepal; leaf blades mostly 7-10 times as long as wide; plants predominantly of coastal marshes and shorelines

R. pallidus Bigelow

6b. Inner tepals with a narrow tubercle, the tubercle less than half as wide and much shorter than its associated tepal; leaf blades mostly 2.5-6 times as long as wide; plants predominantly of freshwater wetlands and inland disturbed habitats

R. triangulivalvis (Danser) Rech.f.

5b. Erect stems usually without axillary branches or leaf tufts; leaves broader, oblong-lanceolate or linear-oblong

7a. Leaves oblong-lanceolate, with +/- flat margins; valves to 8 mm long; base of tubercles separated from base of valve; pedicel obscurely jointed near base; stem to 2.5 m tall; plants of wetland habitats

R. brittanica Huds.

7b. Leaves lanceolate, with strongly wavy margins; valves to 6 mm long; tubercles with base even with base of valve or projecting below; pedicel with a conspicuous node near base; stem to 1 m; plants of mostly dry, waste areas

R. crispus L.

4b. Valve margin with bristle-like or spinose teeth

8a. Tubercle usually present on the midrib of only 1 valve of the fruiting calyx; basal leaves broadly to narrowly ovate, long-petioled, often red-veined, crenulate; plants of non-saline habitats

R. obtusifolius L.

8b. Tubercle normally present on all 3 valves of the fruiting calyx; basal leaves narrow to broadly lanceolate; annual plants of brackish or saline habitats

9a. Tubercles +/- narrow-lanceolate, 0.3-0.4 mm wide, less than 1/2 as wide as the associated inner tepals excluding the marginal spines, acute to subacute at the apex, brown to red-brown in life; marginal spines of inner tepals 1-3 mm long

R. fueginus Phil.

9b. Tubercles +/- elliptic, 0.4–0.6 mm wide, almost as wide as the inner tepals excluding the marginal spines, obtuse at the apex, cream to white-yellow in life; marginal spines of inner tepals 1-1.5 (-1.7) mm long

R. persicarioides L.