Invasive Alien Species in Northern Ireland

Spartina anglica, Common Cord-grass

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Spartina anglica
© Graham Day
Spartina anglica
© Graham Day
Spartina anglica
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Spartina anglica C.E.Hubb, auct. non Groves & J.Groves
 
Introduction
Common cord-grass is a vigorous, robust grass of tidal mudflats. It is a fertile plant derived from the sterile Spartina x townsendii H. & J. Groves (Townsend's cord-grass) which itself is a spontaneous hybrid between the North American Spartina alterniflora Loisel and the English native Spartina maritime (Curtis) Fernald. S. x townsendii originated in Southampton Water, in the late nineteenth century. The earliest reports of S. anglica are from several areas of tidal mud on the south coast of England from 1892 onwards. The ability of both Townsend's cord-grass and common cord-grass to colonise and stabilise tidal mud led to them being deliberately planted in other sites around the British Isles.
Common cord-grass has become a major nuisance in Strangford Lough, County Down.
 
Description
Common cord-grass is a robust grass with erect shoots which can reach 1.3m. The flower panicles stand stiffly erect above the leaves, consisting of between 2 12 spikes. The flower spikelets are arranged in two rows. The rather broad leaves are 10 45cm in length, rather firm and smooth. The plants are very deeply rooted in the mud, and spread vegetatively by thick fleshy rhizomes which enable the plant to form extensive colonies.
 
Country of origin
South coast of England.
 
Location in Ireland
The largest population is in Strangford Lough, County Down, where it was introduced as a mud-binder in the 1940s, with rather smaller populations in Carlingford Lough, Dundrum Inner Bay and Lough Foyle (where it accompanies Townsend's cord-grass).
 
Life cycle
Plants are perennial, fast-growing and capable of producing abundant fertile seed. It appears that seed may remain dormant for several years in the substrate. The plant also spreads vegetatively by means of short rhizomes, producing dense, pure colonies or swards. The species is not capable of colonising exposed sites subject to strong wave action.
 
Wildlife and habitat impacts
The major concerns for the spread of this species focus on the reduction of food resources available for wildfowl and wading birds, notably eel-grass (Zostera) beds, and the invertebrates that inhabit the mud of these beds.
 
Key vectors
The initial establishment of colonies in the various coastal sites has been by deliberate planting, with the intention of stabilising and reclaiming tidal mudflats, after which local spread has been by seed dispersal and rhizome extension.
 
What you can do as an individual
None are appropriate.
 
Advice to specific groups relevant to this species
A number of organisations including local authorities, the National Trust, Royal Society for the Protection of Birds and the Environment & Heritage Service have been involved in attempts to control this plant in Strangford Lough, County Down.
 
Management measures
Attempts have been made at various times to control or even eradicate locally this plant from its Strangford Lough sites. These include digging up the plants, covering with opaque polythene sheets, burying under silt and applying herbicides.
Current advice on best practice is given by English Nature at their web site, including recommended herbicides (Dalapon, Glyphosate), digging-up, bulldozing, rotovating, burying, etc. Rotovating may cause problems owing to fragmentation of the rhizomes which can then sprout to form new plants. Mowing or grazing can increase shoot density. Covering with black plastic is generally impractical (sheets blow away). Burying may be the best option, but access problems may inhibit this.
 
Further information
Links
English Nature
JNCC
 
Text written by:
Paul Hackney, Keeper of Botany, Ulster Museum