Invasive Alien Species in Northern Ireland

Hippophae rhamnoides, Sea-buckthorn

Hippophae rhamnoides
© Paul Hackney
Hippophae rhamnoides
Click on map to enlarge
Hippophae rhamnoides L.
 
Introduction
Sea buckthorn is a native of eastern Great Britain introduced to Northern Ireland in the late nineteenth century.
 
Description
A very spiny, tall shrub or small tree reaching about 4m in sheltered places, sometimes forming dense thickets or scrubby woodland. The leaves are silvery grey and narrow. The flowers are small and inconspicuous. Separate male and female flowers are borne on different plants. Female plants produce numerous bright orange berries.
 
Country of origin
East coast of England.
 
Location in Ireland
Deliberately planted for dune stabilisation and now established on some dune systems since the late nineteenth or early twentieth centuries: Murlough, County Down; Portstewart, County Londonderry and Portrush, County Antrim, are the most notable. It is still widely planted for amenity purposes, for example, in roadside plantings, and as a garden shrub or hedging plant.
 
Life cycle
Abundant fruit is produced in September if male and female bushes are growing close together, but these play little part in the spread of the plant. Spread is mainly by rhizomes and layering, and in fact some colonies (for example, Portstewart dunes, County Londonderry) are apparently nearly entirely single-sex.
 
Wildlife and habitat impacts
Sea buckthorn berries provide winter bird food, and it is often recommended for planting for this purpose in gardens. Thickets also provide birds with good cover. The deleterious effects of the species relate to its shading-out of native dune plants and production of floristically-poor dense thickets. Such thickets also inevitably completely alter the character of the local dune habitat, which has direct effects on the composition and balance of the invertebrate fauna.
 
Key vectors
Although birds can carry and distribute viable seed, and bird-sown plants are occasionally encountered, the primary source of the nuisance colonies on Northern Ireland's sand dunes were the initial deliberate plantings of some 100 years or more ago, followed by spread by rhizome growth and layering.
 
Advice to specific groups relevant to this species
Control of this plant is best tackled by the larger conservation organisations, for example, the National Trust.
 
Management measures
With well-established large infestations only physical removal involving cutting or digging up the plants, either by hand or mechanically, is feasible. Herbicide should be applied to remaining stumps. English Nature give an account of the process as applied at Ainsdale National Nature Reserve (see Links).
 
Further information
Links
Succession on Portstewart Dunes
http://members.lycos.co.uk/WoodyPlantEcology/sanddune/succession.htm
Sea buckthorn at Berrow Dunes, Somerset
http://www.sedgemoor.gov.uk/index.cfm?Articleid=1899
Removal from Ainsdale Dunes NNR by mechanical means and herbicide
http://www.english-nature.org.uk/pubs/Handbooks/images/low12.pdf
 
Text written by:
Paul Hackney, Keeper of Botany, Ulster Museum