Gunnera tinctoria | Giant-rhubarb | Gunnaire
Third Schedule listed species under Regulations 49 & 50 in the European Communities (Birds and Natural Habitats) Regulations 2011. (Note: Regulation 50 not yet enacted).
Listed as a schedule 9 species under Articles 15 & 15A of the Wildlife Order (Northern Ireland) 1985 (Article 15A not yet enacted).
Regulated invasive species of Union concern under the European Regulation on the prevention and management of the introduction and spread of invasive alien species [1143/2014].
First reported in the wild
Invasive species - risk of High Impact
Introduction pathways - 1
Escape from Confinement
Introduction pathways subclass - 1
NAPRA Ireland risk assessed
Yes. This species underwent a Non-native species APplication based Risk Analysis in 2014.
Overall risk of this species to Ireland is categorised as: MAJOR with a MEDIUM level of confidence.
Overall conclusion summary (Excerpt): Gunnera tinctoria produces large numbers of seeds, which are dispersed by wind, water and birds; it also spreads clonally, by a horizontal rhizome system (Gioria and Osborne, 2013). Long-distance seed dispersal seems to be central to the colonisation of new areas (Gioria and Osborne, 2013). Dispersal of the species is strongly associated with human activities. It is targeted for eradication but such control measures are known to have failed (Armstrong, 2008; Sheehy Skeffington and Hall, 2011).
The species has the potential to expand its invasive range. Gunnera tinctoria invasions may result in a range of environmental, economic and societal impacts. Of much concern is the impact to indigenous biodiversity, alterations to ecosystem function and the provision of ecosystem services. Control and/or eradication of the species will impact on the Irish economy, particularly in counties Galway and Mayo.View the full risk assessment:
Giant rhubarb is a huge herbaceous perennial plant with rhubarb like leaves that grow up to 2m across are rough textured with jagged toothed lobes (Stace, 1997). The two rounded lobes at the leaf base are separated by a deep division and the leaf stalks are stout up to 1.5 m long with green bristles. The flowering spike is cone shaped up to 1m long with densely-packed short stubby branches (<5cm) with 1mm stalk-less reddish-green flowers. Flowering June to August. Fruits are small orange-red berries. Rhizomes 6–25 cm in diameter, mainly horizontal and above-ground, up to 3.5m long. Plant dies-back in winter. Can be difficult to tell apart from the non-invasive Gunnera manicata with diagnostic features only visible when plants are fully developed and flowering/fruiting. May also be confused with occurrences of cultivated rhubarb in the wild.
Crowds out native plants and significantly alters the seed bank community (Gioria & Osborne, 2009). In areas where Gunnera is present it can represent 53 - 86% of the seedlings (Gioria & Osborne, 2009) and additionally alters the seed bank so that it is dominated by agricultural weeds (Gioria & Osborne, 2009).
Coastal; Mires, bogs & fens; Grasslands and landscapes dominated by forbs, mosses or lichens; Inland unvegetated or sparsely vegetated habitats; Constructed, industrial or other artificial habitats; Miscellaneous
Number of fruit ranges from 12 000 to 83 000 borne on 1m infructesences on plants in New Zealand (Williams et al., 2005).
Pathway and vector description
Introduced into Ireland as a garden plant it has since escaped (Reynolds, 2002).
Mechanism of impact
There is currently an EU wide ban on the sale, growing and keeping of this plant (European Commission, 2017). Eradication should be attempted but is difficult because of the large number of seeds produced and the plant's ability to reproduce vegetatively from tiny rhizome fragments (Armstrong et al., 2009).
Gunnera tinctoria is a popular garden landscaping plant. Gardeners and other landowners and users should be educated in the identification of this species as well as its ecological impacts. Several Counties have already produced excellent information leaflets. Galway http://biodiversity.galwaycommunityheritage.org/content/places/invasive-species/gunnera and Mayo http://www.mayococo.ie/en/Services/Heritage/GunneratinctoriaGiantrhubarb/
Smaller plants and sparse infestations can be dug up with spades (Armstrong et al., 2009). Monitoring for regrowth and recolonisation should be carried out within a year (Williams et al., 2005).
Heavy machinery such as mini-diggers or excavators can be used to clear large areas (Armstrong et al., 2009). It is essential to remove the entire rhizome (Williams et al., 2005). Consideration must be given to the disposal of the large quantities of plant material.
Glyphosate application is an effective control method (Armstrong et al., 2009). 2,4-d amine and triclopyr are also effective but cannot be used near water. Spraying should be carried out at the end of the growing season before die back (August – September). Repeat applications will be necessary (Williams et al., 2005).
Leaf stalks can be cut and then painted with herbicide. This is useful for large infestations as the removal of the leaves allows better access to the site (Armstrong et al., 2009). Repeat applications will be necessary (Williams et al., 2005).
Herbicides can also be injected by drilling several holes in the rhizome and filling with herbicide (Armstrong et al., 2009). Repeat applications will be necessary (Williams et al., 2005).
Armstrong et al. (2009) suggest disposal by deep burial. Mayo County Council (undated) recommends leaving the material to decay in black plastic or drying out and burning.
Present in a large range of habitats, such as grassland, waterways, roadsides, quarries, bog, heath, coastal cliffs and agricultural fields (Reynolds, 2002).
Established - Widespread. While widespread it is relatively localised with patches of heavy abundance (Reynolds, 2002). Considered invasive on the west coast, possibly due to climatic conditions, with Achill Island having a particularly large abundance. It is found along stream and river banks, lake and pond margins, coastal cliffs, former cultivated fields and disturbed areas such as roadsides, quarries and ditches (Gioria and Osborne, 2013)
Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador and Peru.
Date of first record category
Fifty year date category
Records submitted to Data Centre in 2020
The following map is interactive. If you would prefer to view it full screen then click here.
How can you help
Report any sightings to the National Biodiversity Data Centre. Do not purchase or plant in your garden. Dispose of garden waste and nuisance plants responsibly.
Armstrong, C; Osborne, B; Kelly, J and Maguire, CM. (2009). Giant Rhubarb (Gunnera tinctoria) Invasive Species Action Plan. Prepared for NIEA and NPWS as part of Invasive Species Ireland. http://invasivespeciesireland.com/wp-content/uploads/2011/01/Gunnera_tinctoria_ISAP.pdf Site accessed 6 September 2017.
European Commission. (2017). Invasive Alien Species of Union Concern. European Union, Luxembourg.
Gioria, M., & Osborne, B. (2009). The impact of Gunnera tinctoria (Molina) Mirbel invasions on soil seed bank communities. Journal of Plant Ecology, 2(3), 153-167.
Gioria M, Osborne B (2013) Biological flora of the British Isles: Gunnera tinctoria. Journal of Ecology 2013, 101, 243–264 . doi: 10.1111/1365-2745.12022
Mayo County Council (undated). Invasive Alien Plant Information Leaflet – Giant Rhubarb (Gunnera tinctoria). An action of the County Mayo Heritage Plan 2006–2011. http://www.mayococo.ie/en/Services/Heritage/GunneratinctoriaGiantrhubarb/File,8428,en.pdf Site accessed 6 September 2017.
Reynolds, S.C.P. (2002) A catalogue of alien plants in Ireland. National Botanic Gardens. Glasnevin, Dublin.
Stace, C. (2002). New Flora of the British Isles 2nd Edition. Cambridge University Press, Cambridge.
Williams PA, Ogle CC, Timmins SM, Cock GDLa , Clarkson J, 2005. Chilean rhubarb (Gunnera tinctoria): biology, ecology and conservation impacts in New Zealand. DOC Research and Development Series. Wellington, New Zealand: Department of Conservation.