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.

Distribution

Mostly w North America.

Discussion

Species 20 (20 in the flora).

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.

Selected References

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

Lower Taxa

Polygonum austiniae, Polygonum bidwelliae, Polygonum bolanderi, Polygonum californicum, Polygonum cascadense, Polygonum douglasii, Polygonum engelmannii, Polygonum heterosepalum, Polygonum hickmanii, Polygonum majus, Polygonum minimum, Polygonum nuttallii, Polygonum paronychia, Polygonum parryi, Polygonum polygaloides, Polygonum sawatchense, Polygonum shastense, Polygonum spergulariiforme, Polygonum tenue, Polygonum utahense

Key

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