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Genus Persicaria Family Polygonaceae

Description: Annual or perennial, erect or decumbent herbs, occasionally rhizomatous.

Leaves petiolate or subsessile, mostly paler beneath, not articulate, nectaries absent; ocrea tubular, brown, membranous, entire, mostly long-ciliate on the upper margin, occasionally with a green limb.

Flowers usually bisexual, clustered in terminal or axillary spike-like inflorescences (usually long, occasionally short and capitate), usually forming panicle-like compound inflorescences Perianth segments 4 or 5, usually distinctly petaloid, pink, white or occasionally green, slightly enlarged in fruit. Stamens 4–8; anthers versatile. Style bifid or trifid, mostly short. Stigmas capitate, smooth.

Achene lenticular or trigonous, enclosed in persistent perianth.


Habit
Photo J. Plaza

Flower
Photo A. J. Perkins

Distribution and occurrence: World: c. 150 spp., cosmop. Aust.: 15 spp., all States.

Previously treated as a section of Polygonum. Leaves of some species may cause dermatitis in stock and humans. Forms of P. orientalis, P. filiformis (Thunb.) Nakai and P. odorata (Lour.) Soják are occasionally cultivated.

Text by K. L. Wilson (1990); edited KL Wilson (Dec 2012; Jan 2014)
Taxon concept:

 Key to the species 
1Inflorescence small, 1–several few-flowered clusters or very short loose spike-like racemes on slender branches; stems creeping, prostrate to decumbent2
Inflorescence of numerous flowers in mostly dense, elongated or more rarely subglobose spike-like racemes, usually arranged in large panicles; stems erect to decumbent or prostrate, occasionally with slender antrorse or spreading hairs but never strongly retrorse-strigose5
2Stems strongly retrorse-strigose; perianth not enlarged or changing colour when fruiting3
Stems not retrorse-strigose; peranth enlarged, succulent, blue-black and surrounding the fruit
                       Back to 1
Persicaria chinensis
3Leaf bases hastate, sagittate or occasionally truncate4
Leaf bases acute to cuneate, occasionally obtuse to truncate
                       Back to 2
Persicaria dichotoma
4Inflorescence of 2–4 branches with small terminal subglobose flower clusters 5–10 mm long with bracts crowded at ends of branches; inflorescence branches with stalked glandular hairs and usually some shorter simple hairs; leaves 15–32 mm widePersicaria strigosa
Inflorescence of 2 or 3 branches but bracts 5–15 mm apart so that flowers appear solitary; inflorescence branches with stalked glandular hairs only or with a few simple hairs as well; leaves 6–17 mm wide
                       Back to 3
Persicaria praetermissa
5Spikes globose or ovoid or short-cylindrical with length no more than twice as great as diam. (occasionally slightly more in Persicaria maculosa and then spikes interrupted below)6
Spikes elongate-cylindrical, at least four times as long as wide
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8
6Ocreas not developed into a green limb; perianth pink to whitish, not thickened and corky7
Ocreas developed into spreading green toothed limb; perianth green, becoming truncate, thickened and corky in fruit
                       Back to 5
Persicaria prostrata
7Perianth c. twice as long as the nut; inflorescence bracts subtriangular, stiff; plants prostrate; spikes ovoid or globose, dense, not interruptedPersicaria capitata
Perianth only slightly exceeding nut; inflorescence bracts funnel-shaped, soft-textured; plants ascending or erect; spikes short-cylindrical, dense but often interrupted below
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Persicaria maculosa
8Ocreas developed on upper margin into a spreading green limb9
Ocreas not developed into green limb
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10
9Large erect herb; perianth pale pink, not becoming thick and corky in fruit; ocrea limb collar-like, to 7 mm wide, entire; leaf base obtuse, often slightly oblique and petiole winged for 1–2 cmPersicaria orientalis
Small decumbent to prostrate herb; perianth green, becoming truncate, thickened and corky in fruit; ocrea limb lobed and toothed; leaf base attenuate
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Persicaria prostrata
10Stalked glandular hairs present on most parts, occasionally sessile glands present too; simple hairs present on leaf marginsPersicaria elatior
Hairs simple on stems or absent, but sessile glands may be present on stem, leaf, ocrea or perianth
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11
11Stigmas tough and persistent on fruit, hook-likePersicaria filiformis
Stigmas remaining delicate when fruiting, usually deciduous
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12
12Plants glabrous or with hairs only on leaf margins, veins and ocreas13
Plants hairy, usually densely so, not just on leaf veins and margins
                       Back to 11
16
13Perianth densely glandular, pink to whitish or greenish white14
Perianth not densely glandular, pink to white
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15
14Perianth greenish white; upper margins of ocreas mostly with cilia 3–5 mm long; petioles 1–5 mm long; spikes slender, lax, with each flower cluster distinctPersicaria hydropiper
Perianth pink to whitish; ocreas without marginal hairs; petioles 5–22 mm long; spikes dense, with flowers crowded and overlapping
                       Back to 13
Persicaria lapathifolia
15Leaves with glands (usually yellow) dense on lower surface and scattered on upper; spikes dense, 4–7 mm diamPersicaria lapathifolia
Leaves not conspicuously glandular but usually minutely warty, often with purplish blotch near the middle of the upper surface; spikes slender, rather lax, 3–4 mm diam
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Persicaria decipiens
16Leaves subsessile, petiole no more than 2 mm longPersicaria subsessilis
Leaves obviously petiolate, petiole 5–40 mm long
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17
17Plants erect; perianth sparsely sessile-glandular; leaves densely to sparsely tomentose, sometimes mixed with more or less glabrous leaves on same plantPersicaria lapathifolia
Plants decumbent; perianth not glandular; leaves not tomentose but densely and shortly pubescent beneath, hairs on upper surface more or less densely and coarsely antrorse
                       Back to 16
Persicaria attenuata

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