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This species belongs to the knotgrass family, Polygonaceae. The common name, knotgrass, refers to the swollen nodes of the stems which appear as joints or knots.

Polygonum maritimum (sea knotgrass)

[KSP]

Kew Species Profiles

General Description

Sea knotgrass is a coastal plant and is the rarest of the knotgrasses in Britain.

This species belongs to the knotgrass family, Polygonaceae. The common name, knotgrass, refers to the swollen nodes of the stems which appear as joints or knots.

Species Profile
Geography and distribution

Polygonum maritimum is native to a few coastal sites in southern England, the Channel Islands and one locality in southern Ireland, but it is also found on the west coast of France southwards to the Mediterranean region, and Macaronesia.

Description

Overview: The sea knotgrass is a perennial, with herbaceous weak stems that are woody below and grow up to 50 cm in length; the stems are procumbent.

Leaves: The leaves are somewhat oblong and leathery in texture with inrolled margins. The leaf stipules are a very conspicuous and characteristic part of the plant; they are silvery, forming a sheath at the base of leaves and cover part of the stem.

Flowers:  The flowers are in inflorescences in the axils of leaves and are reddish or pink with five perianth lobes about 4 mm long.

Fruits: The fruit (achene) is dark brown, shiny and is longer than the perianth.

The flowering and fruiting period is July-September.

Threats and conservation

Polygonum maritimum is the rarest of the knotgrasses in Britain. It is sporadic along the coast of Cornwall, Devon, Hampshire (including the Isle of Wight) and the Channel Islands. Since the 1960s its range has extended in England, its recent spread correlated with a run of mild winters and hot summers.

Uses

The leaves of the sea knotgrass are used as a dressing for burns. Perhaps in view of the recent extension of its range in England which is reported to be correlated with changes in the climate, it could act as an indicator species for climate change.

Millennium Seed Bank: Seed storage

Kew's Millennium Seed Bank partnership aims to save plant life world wide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.

Number of seed collections stored in the Millennium Seed Bank: Six

Seed storage behaviour: Orthodox (the seeds of this plant survive being dried without significantly reducing their viability, and are therefore amenable to long-term frozen storage such as at the MSB)

Germination testing: Successful

Distribution
France, Ireland, United Kingdom
Ecology
Sandy beaches
Conservation
Rare
Hazards

Not known

[KSP]
Use
Dressing for burns. Potential as an indicator species for climate change.

Native to:

Albania, Algeria, Azores, Baleares, Bulgaria, Canary Is., Cape Provinces, Corse, Cyprus, East Aegean Is., Egypt, France, Great Britain, Greece, Ireland, Italy, Kriti, Krym, Lebanon-Syria, Libya, Madeira, Morocco, Netherlands, Palestine, Portugal, Romania, Sardegna, Sicilia, Spain, Transcaucasus, Tunisia, Turkey, Turkey-in-Europe, Yugoslavia

Introduced into:

Argentina Northeast, Argentina Northwest, Argentina South, Chile Central, Chile South, Falkland Is., Pakistan, West Himalaya

English
Sea knotgrass

Polygonum maritimum L. appears in other Kew resources:

Date Reference Identified As Barcode Type Status
s.coll. [s.n.], Massachusetts K000831005
Lewis, R. [540], Falkland Is. K000299181

First published in Sp. Pl.: 361 (1753)

Accepted by

  • Akeroyd, J.R. (2013). Docks and Knotweeds of Britain and Ireland: 1-258. Botanical Society of Britain and Ireland.
  • Authier, P. & Covillot, J. (2011). Catalogue actualisé des plantes de l'île de Rhodes (Grèce) Saussurea; Travaux de la Société Botanique de Genève 41: 131-170.
  • Boulos, L. (1999). Flora of Egypt 1: 1-419. Al Hadara Publishing, Cairo.
  • Broughton, D.A. & McAdam, J.H. (2005). A checklist of the native vascular flora of the Falkland Islands (Islas Malvinas): New information on the species present, their ecology, status and distribution Journal of the Torrey Botanical Society 132: 115-148.
  • Danin, A. & Fragman- Sapir, O. (2019). Flora of Israel Online http://flora.org.il/en/plants/.
  • Davis, P.H. (ed.) (1967). Flora of Turkey and the East Aegean Islands 2: 1-581. Edinburgh University Press, Edinburgh.
  • Dobignard, A. & Chatelain, C. (2013). Index synonymique de la flore d'Afrique du nord 5: 1-451. Éditions des conservatoire et jardin botaniques, Genève.
  • Germishuizen, G. & Meyer, N.L. (eds.) (2003). Plants of Southern Africa an annotated checklist Strelitzia 14: 1-1231. National Botanical Institute, Pretoria.
  • Lambion, J., Delvosalle, L. & Duvigneaud, J. (2004). Nouvelle flore de la Belgique du G. D. de Luxembourg, du Nord de la France et des régions voisines, ed. 5: 1-1167. Edition du Patrimoine du Jardin botanique national de Belgique.
  • Mateos, M.A. & Valdés, B. (2009). Catálogo de la flora vascular del Rif occidental calizo (N de Marruecos). I Selaginellaceae - Rosaceae Lagascalia 29: 105-257.
  • Meikle, R.D. (1985). Flora of Cyprus 2: 833-1970. The Bentham-Moxon Trust Royal Botanic Gardens, Kew.
  • Musselman, L.J. (2011). Checklist of Plants of Lebanon and Syria http://ww2.odu.edu/~lmusselm/plant/lebsyria/Checklist%20of%20Lebanon%20Plants.pdf.
  • Qaiser, M. (2001). Flora of Pakistan 205: 1-190. Department of Botany, University of Karachi, Karachi.
  • Takhtajan, A.L. (ed.) in Takhtajan, A.L. (ed.) (2012). Konspekt Flora Kavkaza 3(2): 1-623. Editio Universitatis Petropolitanae.
  • Tutin, T.G. & al. (eds.) (1993). Flora Europaea ed. 2, 1: 1-581. Cambridge University Press.
  • Zuloaga, F.O. & Belgrano, M.J. (eds.) (2020). Flora Argentina. Flora vascular de la República Argentina 19(1): 1-378. INTA, IMBIV & IBODA.
  • Zuloaga, F.O., Morrone, O. , Belgrano, M.J., Marticorena, C. & Marchesi, E. (eds.) (2008). Catálogo de las Plantas Vasculares del Cono Sur Monographs in Systematic Botany from the Missouri Botanical Garden 107: 1-3348. Missouri Botanical Garden.

Literature

Kew Species Profiles

  • Clapham, A.R., Tutin, T.G. & Warburg, E.F. (1962). Flora of the British Isles. Cambridge University Press, Cambridge.
  • Preston, C.D., Pearman, D.A. & Dines, T.A. (eds) (2002). New Atlas of the British and Irish Flora: An atlas of the vascular plants of Britain, Ireland, the Isle of Man and the Channel Islands. Oxford University Press, Oxford.
  • Uphof, J.C. Th. (1959). Dictionary of Economic Plants. Engelmann, New York.

Kew Backbone Distributions

  • Authier, P. & Covillot, J. (2011). Catalogue actualisé des plantes de l'île de Rhodes (Grèce) Saussurea; Travaux de la Société Botanique de Genève 41: 131-170.
  • Boulos, L. (1999). Flora of Egypt 1: 1-419. Al Hadara Publishing, Cairo.
  • Broughton, D.A. & McAdam, J.H. (2005). A checklist of the native vascular flora of the Falkland Islands (Islas Malvinas): New information on the species present, their ecology, status and distribution Journal of the Torrey Botanical Society 132: 115-148.
  • Danin, A. & Fragman- Sapir, O. (2019). Flora of Israel Online http://flora.org.il/en/plants/.
  • Davis, P.H. (ed.) (1967). Flora of Turkey and the East Aegean Islands 2: 1-581. Edinburgh University Press, Edinburgh.
  • Dobignard, A. & Chatelain, C. (2013). Index synonymique de la flore d'Afrique du nord 5: 1-451. Éditions des conservatoire et jardin botaniques, Genève.
  • Germishuizen, G. & Meyer, N.L. (eds.) (2003). Plants of Southern Africa an annotated checklist Strelitzia 14: 1-1231. National Botanical Institute, Pretoria.
  • Mateos, M.A. & Valdés, B. (2009). Catálogo de la flora vascular del Rif occidental calizo (N de Marruecos). I Selaginellaceae - Rosaceae Lagascalia 29: 105-257.
  • Meikle, R.D. (1985). Flora of Cyprus 2: 833-1970. The Bentham-Moxon Trust Royal Botanic Gardens, Kew.
  • Musselman, L.J. (2011). Checklist of Plants of Lebanon and Syria http://ww2.odu.edu/~lmusselm/plant/lebsyria/Checklist%20of%20Lebanon%20Plants.pdf.
  • Qaiser, M. (2001). Flora of Pakistan 205: 1-190. Department of Botany, University of Karachi, Karachi.
  • Takhtajan, A.L. (ed.) in Takhtajan, A.L. (ed.) (2012). Konspekt Flora Kavkaza 3(2): 1-623. Editio Universitatis Petropolitanae.
  • Tutin, T.G. & al. (eds.) (1993). Flora Europaea ed. 2, 1: 1-581. Cambridge University Press.
  • Zuloaga, F.O., Morrone, O. , Belgrano, M.J., Marticorena, C. & Marchesi, E. (eds.) (2008). Catálogo de las Plantas Vasculares del Cono Sur Monographs in Systematic Botany from the Missouri Botanical Garden 107: 1-3348. Missouri Botanical Garden.

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© Copyright 2017 World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

Kew Names and Taxonomic Backbone
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

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