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National Botanic Gardens Home Page

vert bar Carpobrotus edulis
Last updated 15 September 2011

STATUS
Carpobrotus edulis, or Hottentot Fig, is an aggressive invader of coastal habitats on the drier eastern coasts of Ireland, and totally smothers indigenous maritime plant communities.
At present there are probably just 11-12 populations of the species (see map right and details below).
In Cornwall and the Channel islands the species is a considerable nuisance, and In Ireland we still have the potential to prevent the species getting too strong a foothold.

CONTROL
Unlike many other invasive species, money is not the limiting factor in removal of Hottentot Fig. The limiting factors are largely time and manpower. Physical removal must be undertaken with care since stems can be removed by nesting seabirds such as shags and cormorants and incorporated into nests, exacerbating the problem.
Extensive removal may result in erosion of exposed and de-vegetated substrates.
Our experiences on Howth head with chemical control (see below) have been very successful, resulting in rapid and extensive recolonisation of the dead mats of Carpobrotus by Inula, Crithmum and other characteristic cliff plants.

Eradication of Carpobrotus in Minorca:
28 ha of Carpobrotus was present in 2002. By 2005, 24 ha have been eradicated and 900 tons of Carpobrotus remains had been moved. The transport of eradicated plants was a major problem. Threat is now minimised in Minorca, with Carpobrotus remaining in just two places. Landowner opposition remains an issue in eradicating these last populations.

Global Invasive Species Database


ACTIONS
On the Murroughs in County Wicklow (right) there are two patches of Carpobrotus edulis to the north of the Breaches, each about 15 x 2-3 metres in extent, and one smaller patch to the south of the Breaches.
In March 2007, 2 square metres were removed from one patch and transported off the site in black plastic sacks (below).
Beneath the dense mat of stems the soil was totally devoid of other vegetation.
The area was monitored over the summer to determine the success of the removal.
In 2010 the Heritage Council made a generous gratn towards control costs, and extensive chemical control was undertaken on Howth head and at a number of smaller sites along the east coast. In 2011 a further grant from Heritage Council has allowed the project to expand to the target of eradication of the plant in all known wild populations as well as an opportunity to follow up previous work. In August/September 2011 resurvey work on Howth head has demonstrated not only the efficacy of the control measures, but a remarkable reappearance of native vegetation cover.
See here for more information ...



Local botanists have been contacted to assess the size of the other known populations to determine the level of effort required for each site.



Status of the invasive alien Carpobrotus edulis on Howth Head, Co. Dublin, and options for its control (pdf document).
A brief description and location of each of the colonies on Howth Head is given, with proposals for its control at each site. The Heritage Council has generously given us a grant towards this work, which will be undertaken by the National Botanic Gardens in collaboration with Fingal County Council.




Herbicide trials 2010
During May 2010, a herbicide trial was conducted on a population in County Wicklow. The results were used to select appropriate chemicals and methods to tackle the Howth Head populations






Carpobrouts eradication project, Howth Head 2010
During September 2010, a major eradication project was begun on Howth Head, funded through the Biodiversity grants scheme run by the Heritage Council. The six sites at Howth were chemically treated between the 8th and the 20th of September 2010 during dry calm days.
A wheelbarrow power sprayer (KS, 120 litre tank, petrol motor) which was easily wheeled to access points along the cliff path and the 30m hose extension to the tank meant that operators could access the Hottentot fig without having to wear a cumbersome knapsack sprayer. Volunteer labour was used and the chemical (3 g/l glyphosate and 0.3g/l diquat) was mixed on site. Water was brought along in drums and transported by wheelbarrow once on site.




Return of the Natives, Howth Head 2011
During August 2011, a survey was undertaken of all the areas treated in 2010 as part of a further Biodiversity grant from the Heritage Council.
The survey indicated a success rate of 97% for all treated areas.
The most heartening result, however, has been the phenomenal success of the native flora in recolonising the vast mats of dead Hottentot fig. In some areas the dead plants have been totally covered, in others it is clear that just one year on, many native plants are recolonising areas from which they had been totally displaced. Overall native plants are now covering some 20% of the treated areas. This result is much better than we had hoped for and gives us much greater optimism that re-generation of the Carpobrotus will be made very difficult by a healthy canopy of these native plants.
Overlooked sites and small areas that escaped in 2010 were re-sprayed in September.





Known Sites for Carpobrotus edulis (based on Reynolds (2002) with additions):
Vice-County Location
3 Little Island Strand, Ownahincha, Co. Cork, 21/07/2011, W312 352, On cliffs at east end of beach. First seen 2010.[TREATED 2011]
5 Near Roche’s Point, Cork Harbour 1978, 1985 (DBN); still there 1999 (Scannell, M.J.P. Cloyne, East Cork (H5), 26-27 June 1999 (Ir. Bot. News No. 10: 50-53). W 826 601, Spreading rapidly, with ca.40 patches some 5 sq m in size, N.Smyth 2011.
6 Garrarus 2000, coastal cliffs (Green, P.[R.] (2001b) Recording in Co. Waterford (v.c. H6) in 2000, X548984. Ir. Bot. News No. 11: 37-41).[TREATED 2011]
Dungarvan, P.R.Green, 1974; X2793.[Not seen in 2011]
Ballynamona, P.R.Green & J.Wallace, X1677 [Not seen in 2011]
12 Atlas record: T01Y; Carna, T10L…[Not seen in 2011]
20 The Murrough 1972, sparingly in a few places: The Breaches S of Kilcoole Station 1994, by railway (D. Nash), also 1999 (SR). – 2 patches each about 15 x 2-3 m in extent (M.Jebb) [TREATED 2010]
N of Arklow, 1972, T 28265 78570 (Carvill, P.H. & Curtis, T.G. (1973) New plant records for County Wicklow. Ir. Nat. J. 17: 386-388). [TREATED 2011]
Greystones harbour. Planted at back of harbour (MJ).[Not seen 2010]
21 * Howth; map record (Atlas 1962). S coast of Howth from W of Drumleck Point to Baily Lighthouse 1989-90 (FDub 1998, DBN), and still extensively naturalized there 2001 (SR).[TREATED 2010 & 2011]
220m E of Sutton Dinghy Club. [TREATED 2010]
Bull Island, 600m S of Visitor Centre.[TREATED 2010]
Rockabill 1990 (FDub 1998).
31 Coast S of Clogher Head mid-1990s (M. Taylor). [Not seen in 2010 (D.Lupton)].
38 Cranfield by Carlingford Lough 1980, J269104, on sand;
Orlock Point, 1984, J555835, abundant on rocks by shore (FNE 1992).
Near Annalong, J31U, National Invasive Species Database.

CONTACTS
If you have information about any other populations of Carpobrotus please notify the following:-
Matthew Jebb
National Botanic Gardens
Glasnevin
Dublin 9
matthew.jebb at opw.ie