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. .