Polygonum oxyspermum

Tracheophyta MagnoliopsidaPolygonaceaePolygonumPolygonum oxyspermum

Ecology

A prostrate annual, biennial or short-lived perennial of sand, shingle or shell beaches, sometimes found on other open sandy ground near the sea, usually just above the limit of the highest tides. Lowland.

Status

Native

World Distribution

European Wide-temperate element; also in N. America.

Broad Habitats

Supralittoral sediment (strandlines, shingle, coastal dunes)

Light (Ellenberg): 9

Moisture (Ellenberg): 6

Reaction (Ellenberg): 7

Nitrogen (Ellenberg): 8

3

Salt Tolerance (Ellenberg): 3

January Mean Temperature (Celsius): 4.6

July Mean Temperature (Celsius): 14.8

Annual Precipitation (mm): 1102

Life form information

Height (cm): 20

Perennation - primary

Annual

Life Form - primary

Therophyte (annual land plant)

Woodiness

Herbaceous

Clonality - primary

Little or no vegetative spread

Count of 10km squares in Great Britain: 305

Count of 10km squares in Ireland: 75

Count of 10km squares in the Channel Isles: 9

Atlas Change Index: 0.01

Distribution information

JNCC Designations

NHMSYS0000461871

Scarce Atlas Account

Scarce Atlas Account: 

Polygonum oxyspermum C. Meyer & Bunge ex Ledeb.

Ray's knotgrass

Status: not scarce

 

This is a characteristic but local plant of strandlines on coastal sand, shingle and silty mud. Associated species include Atriplex glabriuscula, A. laciniata, Cakile maritima and Salsola kali. It also occurs above the strandline in embryonic foredunes.

It is an annual or short-lived perennial and is probably largely self-pollinated. It flowers from July to October.

This species has declined in some areas. It has always been rare in eastern England. Strandline plants are notoriously erratic in appearance (Webb & Akeroyd 1991), so disappearance from a particular locality does not always imply a decline. Nevertheless, this plant has suffered from the increased disturbance of many beaches, with consequent damage to strandline and foredune communities. It may be under-recorded on the west coast of Scotland.

The species occurs along most of the coasts of Europe, except southern and western Spain (Jalas & Suominen 1979). Subsp. raii extends from north-western Spain to arctic Russia, with almost indistinguishable plants from the coasts of the Black Sea having been called P. mesembricum. Subsp. oxyspermum, with longer, more greenish-brown fruits than subsp. raii, occurs in the Baltic and southern Norway. Longer-lived perennial plants from the western and central Mediterranean coasts belong to subsp. robertii (an epithet erroneously ascribed to British material in the past). 

The British plant is subsp. raii (Bab.) D. Webb & Chater. Some plants from Scotland, especially from Arran, are close to subsp. oxyspermum and require further investigation.

 

J. R. Akeroyd

PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.

Atlas text references

Atlas (173c)
Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols,
Hultén, E., and Fries M.
, Königstein, (1986)

Jalas & Suominen (1979)
Docks and knotweeds of the British Isles. Botanical Society of the British Isles Handbook no. 3,
Lousley, J. E., and Kent D. H.
, London, (1981)

Scarce plants in Britain,
Stewart, A., Pearman D. A., and Preston C. D.
, Peterborough, (1994)

The taxonomy of Polygonum aviculare and its allies in Britain,
Styles, B. T.
, Watsonia, Volume 5, p.177-214, (1962)