Persicaria amphibia (L.) Delarbre - Water Smartweed


 

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Persicaria amphibia - (image 1 of 7)

 

Taxonomy

Family: Polygonaceae

 

Synonymous with Polygonum amphibium L.

Habitat

Wet soil and shallow water of marshes, bogs, shores.

Associates

 

Distribution

Widespread in the Northern Hemisphere and in South Africa. Variety amphibium occurs only in Europe.

Morphology

Rhizomatous perennial, functionally dioecious; aquatic, emergent or terrestrial; stems glabrous or pubescent, often branched, floating in aquatic forms, erect or ascending in terrestrial forms to 1 m; leaves mainly cauline, alternate; terrestrial form with lance-acuminate, hairy leaves; aquatic forms with floating, glabrous, elliptic and obtuse or rounded leaves; ocreae fringed or not, often with a flared collar in aerial forms; flowers in stout, terminal, solitary or paired racemes, subtended by ocreolae; tepals 5, pink to reddish, rounded above, united below, 4-5 mm at anthesis; outer tepals not keeled or winged at maturity; styles short, withering in fruit.

Notes

Flowers June to October

Wetland indicator: OBL

The specific epithet refers to the phenotypic plasticity of this species in response to changes in water level. Two varieties are recognized in the northeastern U.S.:

var. stipulaceum N. Coleman is aquatic-adapted and will not flower when stranded, with inflorescences up to 4 cm and leaves that are glabrous, floating, and elliptic; stipules often with an herbaceous flange. Sometimes treated as spp. laevimarginata (Hult.) Soják.

var. emersum Michx. is terrestrial or strongly emergent from shallow water, lacking floating leaves or shoots, with inflorescences 4-15 cm and glandular-hairy peduncles, and leaves that are hairy and acuminate, with stipules lacking an herbaceous flange; Polygonum coccineum in Swink & Wilhelm would be referable to this variety.

Typical P. amphibia is native to Eurasia and exhibits traits intermediate between the North American varieties; it may be naturalized in NY.

References

Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. Second Ed.

The New York Botanical Garden. Bronx, NY

 

Swink, F. and G. Wilhelm. 1994. Plants of the Chicago Region.
Indiana Academy of Science. The Morton Arboretum. Lisle, Illinois.

 


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 Michael Hough © 2009