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vert bar Gunnera tinctoria (Giant rhubarb)
Last updated 30 November 2009

STATUS

Gunnera tinctoria is currently considered invasive on the west coast of Ireland, although it is also found on the east coast to date it is not considered invasive. It is considered to be having a significant impact on Achill Island, County Mayo, where is has spread throughout.

It is thought it was originally bought over as an ornamental plant; first records of it are as far back as 1939 (Praeger). Its native range is mainly from southern Chile, where climatic conditions are similar to those found on the west coast, high annual rainfall and temperatures rarely falling below 0º C.

In Ireland it is now found on coastal cliffs, waterways, roadsides, wet meadows and derelict gardens and fields. It propagates both by seed and by vegetative means. In early spring its leaves begin to grow and in a couple of weeks can reach over 2 meters in height. Its large leaves (up to 2m wide) and fast growth shade all plants growing below. In the winter the leaves die back leaving the exposed rhizomes.



IDENTIFICATION

Whilst Gunnera is difficult to confuse with any other species in the Irish flora, or in an Irish garden, the differences between G.tinctoria and G.manicata are less obvious and in view of the fact that the former is highly invasive and the latter apparently not (as yet), it is important to distinguish between them.

The most reliable method is the apperance of the inflorescence: on the right is an image of the two inflorescences: G.tinctoria on the left, and G.manicata on the right.



CONTROL

Control has been focused on the use of herbicides. Currently trials are being carried out in Dooega, Achill Island using RoundUp (glyphosate) and Garlon (triclopyr).

There has been initial success, although it is expected that further applications will be necessary due to the large rhizome of fully established plants.

In New Zealand, where it is also invasive, there have been experiments with several herbicides for a number of years and aerial spraying over large areas has been conducted. The New Zealand Department of Conservation (DoC) have reported their suggestions on the control of G. tinctoria. (Williams et al. 2005).



ACTIONS

Mayo County Council, the Heritage Council, National Parks and Wildlife Services, the Biodiversity Fund and UCD have jointly funded a project to carry out experiments on the development of measures for the control of G. tinctoria.

Alongside the experiments a mapping project of Achill Island is being conducted. The mapping will provide a baseline for future projects to monitor its spread and the success of control. It will provide an insight into the habitats at risk of invasion, its means of spread and where prevention could be introduced as a means of control. Currently as part of this project an information leaflet for landowners is being produced.




DISTRIBUTION
Reynolds (2002): Fairly common escape from cultivation, mainly in W and SW; naturalized extensively in parts of W Mayo (Achill Island and Curraun) and W Galway (Connemara); boggy ground, damp pastures, ditches, roadsides, by streams etc.; freely seeding, and also spreading from discarded plants or from where originally planted; considered an invasive species, the effect of G. tinctoria on semi-natural grassland habitats has been studied (Hickey & Osborne 1998).

* Naturalized and plentiful by mid-1930s on rough hillsides on S side of Killary Harbour below Leenane in W Galway; also N side of Killary Harbour, and on shore and in gullies on S side of Curraun Achill in W Mayo (as G. manicata in Praeger 1939; see FCB 1983).

Known Sites for Gunnera tinctoria (based on Reynolds (2002) :
Vice-County Location
1 Valencia Island 1994, by coast road S of Knightstown (SR).
3 Durrus 1979 (Scannell & Synnott 1990, DBN). Bantry, Castletownberehaven and Glengarriff area 1989 (Campbell & Osborne 1990). Near Rosscarberry 1993 (SR). Bere (Bear) Island, roadsides; Whiddy Island, extensively naturalized on low sea cliffs 1997 (L. Wolstenholme).
6 Cappoquin 2001, two plants by river, discarded or possibly planted (P. Green).
10 Shore of Lough Derg near Waterloo Lodge 1972 (Nash 1991).
16 Near Leenane mid-1930s (as G. manicata in Praeger 1939). Seedlings above Leenane Hotel 1957 (as 26 in Wallace 1960; see Synnott 1986). Abundantly naturalized in much of N and W Connemara (Scannell & McClintock 1974, FCB 1983, DBN, TCD).
21 Howth 1991, in wet birch grove (FDub 1998).
27 Near Leenane mid-1930s and Curraun Achill (as G. manicata in Praeger 1939). Bangor Erris 1957 (Wallace 1960). Clare Island 1968 (McClintock 1969); also 1984 (Doyle & Foss 1986). NW of Leenane 1973 (Scannell & McClintock 1974). Serious weed of damp pastures in SE part of Achill Island (FCB 1983). Achill Beg (Synnott 1986). Clare Island (Armstrong 2007)
28 Lissadell estate; Ballyconnell, roadside (Cotton & Cawley 1993).
34 Carrick 1989, near Glen River (Campbell & Osborne 1990).
38-40 Frequently planted by streams in estates and large gardens, and often almost naturalized (FNE 1992).


CONTACTS
If you have information about any other populations of Gunnera please notify the following:-
Cristina Armstrong or Bruce Osborne
UCD

REFERENCES
Praeger, R.Ll. (1939) A further contribution to the flora of Ireland. Proc. Roy. Ir. Acad. 45B: 231-254.

Reynolds, S.C.P. 2002 A catalogue of alien plants in Ireland. pages 165-166

Williams, P. A., C. C. Ogle, S. M. Timmins, G. D. L. Cock, and J. Clarkson. 2005. Chilean rhubarb (Gunnera tinctoria): biology, ecology and conservation impacts in New Zealand. Department of Conservation, Wellington.