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FNA | Family List | FNA Vol. 5 | Polygonaceae | Polygonum

30b. Polygonum Linnaeus sect. Duravia S. Watson, Amer. Naturalist. 7: 665. 1873.

Duravia (S. Watson) Greene; Polygonum sect. Monticola J. C. Hickman

Shrubs, subshrubs, or annual herbs, sometimes compact and cushionlike (in P. parryi, P. hickmanii, and P. heterosepalum), homophyllous, homocarpic, not succulent, not glaucous. Stems erect or ascending, rarely prostrate, straight or zigzagged, 4-gonous, ribs obscure or absent, smooth or papillose-scabridulous. Leaves: ocrea 4-8-veined, proximal part not pruinose; petiole (or blade when petiole absent) articulated or not to ocrea; blade narrowly linear to subround, rarely coriaceous (P. paronychia, P. shastense, and P. utahense), margins smooth or papillose-denticulate, not rugulose, rarely glaucous adaxially (P. nuttallii); 1-veined or venation parallel (3-veined), secondary veins not conspicuous. Inflorescences usually axillary and terminal, sometimes entirely axillary; cymes 1-6-flowered. Pedicels erect to spreading or reflexed, 0.1-6 mm, sometimes absent. Flowers open, semi-open, or closed; tepals ± monomorphic, outer tepals equaling or somewhat larger than inner, (dimorphic, with outer tepals shorter than inner in P. heterosepalum), apices of outer tepals rounded or acute to acuminate; anthers pink to purple (orange-pink in P. hickmanii). Achenes ovate to elliptic or lanceolate, 3-gonous, shiny or dull, smooth, tubercled, or longitudinally reticulate.

Species 20 (20 in the flora): mostly w North America.

Section Duravia is heterogeneous and future studies may reveal the necessity of further subdivision. Seven species referred by J. C. Hickman (1984) to sect. Monticola (Polygonum cascadense, P. heterosepalum, P. hickmanii, P. majus, P. polygaloides, P. sawatchense, and P. utahense) are here included in sect. Duravia based on leaf, anther, achene, and pollen morphology. Heterocarpy does not occur in sect. Duravia.


Costea, M. and F. J. Tardif. 2005. Taxonomy of the Polygonum douglasii (Polygonaceae) complex with a new species from Oregon. Brittonia 57: 1-27.

1 Plants shrubs or subshrubs   (2)
+ Plants annual herbs   (4)
2 (1) Stems erect, wiry; perianth 2.6-3.2 mm   19 Polygonum bolanderi
+ Stems prostrate or ascending, not wiry; perianth (4.5-)5-10 mm   (3)
3 (2) Ocreae 15-20 mm, distal parts persistent; w coastal dunes   14 Polygonum paronychia
+ Ocreae 3-5 mm, distal parts deciduous; montane habitats   15 Polygonum shastense
4 (1) Leaves not articulated to ocreae, blades mostly linear, rarely linear-lanceolate   (5)
+ Leaves articulated to ocreae, blades subulate, linear-lanceolate to subround   (9)
5 (4) Distal parts of ocreae entire or shallowly dentate   21 Polygonum bidwelliae
+ Distal parts of ocreae disintegrating into fibers   (6)
6 (5) Plants not compact, not cushionlike; stems simple or divaricately branched, 4-40 cm   20 Polygonum californicum
+ Plants compact, often cushionlike; stems simple or branched from base, 1.5-5(-8) cm   (7)
7 (6) Distal parts of ocreae with curly fibers   16 Polygonum parryi
+ Distal parts of ocreae with straight fibers   (8)
8 (7) Tepals ± monomorphic, outer longer than inner   17 Polygonum hickmanii
+ Tepals dimorphic, outer shorter than inner   18 Polygonum heterosepalum
9 (4) Apices of tepals acute to acuminate; achenes light yellow, light brown, or greenish to dark brown, smooth or with longitudinal ridges   22 Polygonum polygaloides
+ Apices of tepals rounded; achenes black, smooth or minutely tubercled   (10)
10 (9) Pedicels reflexed   (11)
+ Pedicels erect or erect to spreading   (14)
11 (10) Ocreae 5-12 mm; perianths and achenes 3-5 mm   (12)
+ Ocreae 3-5 mm; perianths and achenes 1.2-2.6 mm   (13)
12 (11) Flowers open or semi-open; pedicels 0.5-1 mm; perianth tubes 9-17% of perianth lengths   31 Polygonum majus
+ Flowers closed; pedicels 2-6 mm; perianth tubes 20-28% of perianth lengths   24 Polygonum douglasii
13 (11) Achenes usually exserted from perianth; leaf blades linear-oblanceolate, margins smooth   26 Polygonum engelmannii
+ Achenes enclosed in perianth; leaf blades ovate to elliptic or ovate, margins papillose-denticulate   27 Polygonum austiniae
14 (10) Leaf blades with 1 pleat on each side of midrib   23 Polygonum tenue
+ Leaf blades without pleats   (15)
15 (14) Ocreae 4-12 mm, distal parts disintegrating into persistent fibers; perianths (2.8-)3-5 mm; achenes 2.5-5 mm   (16)
+ Ocreae 1-5 mm, distal parts entire to lacerate; perianths 1.8-2.5 mm; achenes 1.5-2.3 mm   (17)
16 (15) Inflorescences dense, cymes ± overlapping at branch tips   30 Polygonum spergulariiforme
+ Inflorescences elongate, cymes widely spaced along branches   25 Polygonum sawatchense
17 (15) Stems 1.5-3.5 cm; leaf blades with margins revolute, touching along midrib   33 Polygonum utahense
+ Stems 2-35 cm; leaf blades with margins flat, or if revolute then never touching along midrib   (18)
18 (17) Flowers open   32 Polygonum cascadense
+ Flowers semi-open or closed   (19)
19 (18) Leaf blades narrowly elliptic, elliptic, ovate, obovate, or subround, green adaxially, margins flat   28 Polygonum minimum
+ Leaf blades linear to narrowly oblong-elliptic, ± glaucous adaxially, margins revolute   29 Polygonum nuttallii


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