Polygonum douglasii — Details

Polygonum douglasii var. latifolium (Engelm.) Greene:
United States (North America)

Anonymous. 1986. List-Based Rec., Soil Conserv. Serv., U.S.D.A. Database of the U.S.D.A., Beltsville. http://www.tropicos.org/Reference/1103
Munz, P. A. & D. D. Keck. 1959. Cal. Fl. 1–1681. University of California Press, Berkeley. http://www.tropicos.org/Reference/1717

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Polygonum douglasii Greene:
Canada (North America)
United States (North America)

Anonymous. 1986. List-Based Rec., Soil Conserv. Serv., U.S.D.A. Database of the U.S.D.A., Beltsville. http://www.tropicos.org/Reference/1103
Voss, E. G. 1985. Michigan Flora. Part II Dicots (Saururaceae-Cornaceae). Bull. Cranbrook Inst. Sci. 59. xix + 724. http://www.tropicos.org/Reference/1700
Gleason, H. A. 1968. The Choripetalous Dicotyledoneae. vol. 2. 655 pp. In H. A. Gleason Ill. Fl. N. U.S. (ed. 3). New York Botanical Garden, New York. http://www.tropicos.org/Reference/1704
Great Plains Flora Association. 1986. Fl. Great Plains i–vii, 1–1392. University Press of Kansas, Lawrence. http://www.tropicos.org/Reference/637
Fernald, M. 1950. Manual (ed. 8) i–lxiv, 1–1632. American Book Co., New York. http://www.tropicos.org/Reference/1327

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Physical Description

Morphology

Comments

Five taxa that have been included in Polygonum douglasii (E. Murray 1982; J. C. Hickman 1984; J. T. Kartesz and K. N. Gandhi 1990) are treated here as distinct species: P. austiniae, P. majus, P. nuttallii, P. sawatchense, and P. spergulariiforme. Hickman noted extensive intergradation and numerous intermediate specimens among those sympatric elements, but qualitative or quantitative characters allow reliable discrimination in most cases (M. Costea and F. J. Tardif 2005), and species are here circumscribed similar to C. L. Hitchcock (1964).

Greene described var. latifolium as having leaf blades and achenes broader than those of var. douglasii. C. L. Hitchcock (1964) recognized the former, but the characters used to distinguish it appear to vary continuously, and reliable separation is not possible.

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Description

Herbs. Stems erect, green, simple or branched, not wiry, 5-80 cm, glabrous or sparsely papillose-scabridulous. Leaves uniformly distributed, articulated to ocreae, basal leaves caducous, distal leaves abruptly reduced to bracts; ocrea 6-12 mm, glabrous or minutely papillose-scabridulous, proximal part cylindric, distal part hyaline, lacerate; petiole 0.1-2 mm; blade 1-veined, not pleated, linear, narrow-oblong, or oblanceolate, 15-55 × 2-8(-12) mm, margins revolute, smooth or papillose-denticulate; apex acute to mucronate. Inflorescences axillary and terminal, spikelike, elongate; cymes widely spaced along branches, 2-4-flowered. Pedicels mostly exserted from ocreae, reflexed, 2-6 mm. Flowers closed; perianth 3-4.5 mm; tube 20-28% of perianth length; tepals overlapping, green to tannish with white or pink margins, petaloid, oblong, cucullate, navicular, apex rounded; midveins usually branched, rarely unbranched; stamens 8. Achenes enclosed in perianth, black, elliptic or oblong to ovate, 3-4(-4.5) mm, faces subequal, shiny or dull, smooth or minutely striate-tubercled.

Flora of North America @ eFloras.org

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Diagnostic Description

Synonym

Polygonum douglasii var. latifolium (Engelmann) Greene; P. emaciatum A. Nelson; P. montanum (Small) Greene; P. tenue Michaux var. commune Engelmann; P. tenue var. latifolium Engelmann

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Type Information

Syntype for Polygonum douglasii Greene
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Original publication and alleged type specimen examined
Preparation: Pressed specimen
Collector(s): S. Watson
Year Collected: 1868
Locality: Ruby Valley., Nevada, United States, North America
Elevation (m): 1829

Syntype: Greene, E. L. 1885. Bull. Calif. Acad. Sci. 1 (3): 125.

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Syntype for Polygonum douglasii Greene
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Original publication and alleged type specimen examined
Preparation: Pressed specimen
Collector(s): S. Watson
Year Collected: 1869
Locality: Bear River Cañon., Utah, United States, North America
Elevation (m): 2134

Syntype: Greene, E. L. 1885. Bull. Calif. Acad. Sci. 1 (3): 125.

Source: National Museum of Natural History Image Collection

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Ecology

Habitat

Habitat & Distribution

Flowering Jun-Oct. Dry, often disturbed places, rock outcrops, sandy ground; 300-3000 m; Alta., B.C., Man., Ont., Que., Sask., Yukon; Ariz., Calif., Colo., Idaho, Iowa, Mich., Minn., Mont., Nebr., Nev., N.H., N.Mex., N.Y., Oreg., S.Dak., Utah, Vt., Va., Wash., Wyo.

Flora of North America @ eFloras.org

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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

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Wikipedia

Polygonum douglasii

Polygonum douglasii is a species of flowering plant in the knotweed family known by the common name Douglas's knotweed. It is native to much of northern and western North America, where it can be found in many types of habitat, including disturbed areas.

This plant species is known as a species complex, as there are many subspecies that may be better treated as species in their own right.^[1]^[2]

The plant is variable in morphology and the subspecies are often difficult to distinguish. In general, plants in this complex are annual herbs growing erect to maximum heights anywhere between 3 and 80 centimeters with thin, angular stems. High-elevation plants are smaller and may be decumbent in form. The leaves are linear or widely lance-shaped, sometimes falling away to leave the plant mostly naked in flowering, or reduced to tiny scales at the stem tips. The flowers are a few millimeters long, pink to white in color, sometimes remaining closed or opening together in a clusterlike inflorescence.

References

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

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