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      Gunnera tinctoria (Photo: J.S. Peterson @ USDA-NRCS PLANTS Database) - Click for full size
    Taxonomic name: Gunnera tinctoria (Molina) Mirbel
    Synonyms: Gunnera chilensis Lam., Gunnera scabra (Ruiz.&Pav.), Panke tinctoria Molina (basionym)
    Common names: Chilean gunnera, Chilean rhubarb, giant rhubarb, nalca, panque
    Organism type: herb
    Gunnera tinctoria is a large herbaceous plant that forms dense colonies that shade out and suppress native vegetation. This species is a vigorous seeder, and birds facilitate its spread. Its ability to reproduce rhizomatically is yet another reason for its invasive nature. Intense effort is required to control this species.
    Description
    Law (2003) states that, "G. tinctoria is a large, clump-forming, herbaceous plant that grows up to 2m in height. It has stout horizontal rhizomes, and massive umbrella-sized leaves on sturdy petioles. The leaves and their stems are covered in rubbery prickles. Tiny green flowers occur in early summer on conical spikes." The Taranaki Regional Council (2003) state that, "G. tinctoria is a perennial with an exotic tropical appearance with spiny stems some 1.5 to 2m tall. The flower stems resemble elongated broccoli and number up to five per plant, standing up to 1m tall and rising from the base of the leaves (each seed head may contain in excess of 80,000 seeds). In severe winter conditions the plant dies down for the winter and grows new leaves in spring."

    Williams et al. (2005) describe G. tinctoria as follows, "G. tinctoria is a summer-green herb, with short, stout, horizontal rhizomes which give rise to stout petioles up to 1000 (1500) 1mm × 45mm that are studded with short reddish prickles. The leaf lamina measures up to about 0.8m × 1.0m with 5-7 lobes. It is very coriaceous, and hairy beneath, especially on the veins. Massive over-wintering buds-up to 250mm long-accumulate on the rhizomes and they are covered in pinkish, pinnatisect scales that extend to the broad leaf midribs. The flowers are borne on panicles that are up to 1m long; usually three or four per plant. Individual flowers are densely packed, sessile, apetalous, with minute sepals, and only c. 1mm long. Style length is slightly less than the ovary. The drupes are reddish, oblong, and 1.5mm-2mm long. Each contains a single ovoid and flanged seed of 1.2mm × 1-1.5mm diameter, weighing 4mg. The hundreds of fruit are regularly arranged and densely packed on the infructescence."

    Occurs in:
    coastland, natural forests, riparian zones, wetlands
    Habitat description
    Gunnera tinctoria has been found in meadows, bogs, gardens, woodlands, sunny edges, and dappled shade. While this species can invade and occupy a variety of habitat it requires moist soils in order to establish (Plants for a Future, 2000). Law (2003) reports G. tinctoria being found on coastal cliffs, riparian zones and wetland areas.

    Williams et al. (2005) describes the soils which are favoured by G. tinctoria in New Zealand. The authors state that the most robust stands of the plant are found growing on colluvium or alluvium (colluvium or hillwash is the name for loose bodies of sediment that has been deposited or built up at the bottom of a low grade slope or against a barrier on that slope, as a result of rainwater or downhill creep by gravity. Alluvium is young sediment—freshly eroded rock particles that have come off the hillside and been carried by streams). G. tinctoria grows on substrates derived from a wide range of sedimentary rocks; in the western North Island where the plant is established, most soils also have a large component of volcanic material.
    The authors further state that G. tinctoria tolerates salt spray and is found growing right up to the high tide mark in the coasrtal areas that it has invaded. The plant is seen to tolerate seasonally water logged wet soils and establishes less on excessively drained and drought-prone sandy or stony soil.

    General impacts
    Law (2003) report that, "G. tinctoria shades out rare and endangered indigenous flora and fauna. The huge leaves of eachG. tinctoria mean it can impact on a disproportionately large number of the comparatively small, native herbs. Areas that have been cleared of mature G. tinctoria can become re-colonized with numerous seedlings from the original plants, and pieces of the rhizomes that break off will also re-grow. In areas with harsh winter frosts, G. tinctoria is deciduous or semi-deciduous. Once established, it is very invasive and forms dense colonies that shade-out or suppress desirable flora. These characteristics have contributed to it being a serious threat to indigenous biodiversity values in areas it has invaded". Weedbusters (2003) report that G. tinctoria can block drains and streams; and obstruct access to natural and recreational areas.
    Uses
    Plants for a Future (2000) reports that young leaf stalks can be peeled and cooked as a vegetable or eaten raw. They are "Acidic and refreshing". G. tinctoria also has medicinal uses as an astringent. This species can also be used as to make a black dye is obtained from the root, and has been used as a roof covering Plants for a Future, 2000).

    Williams et al. (2005) reports that, "In Southern Chile (at latitudes of 36º-42ºS) G. tinctoria is a delicacy associated with Mapuche Indian customs. The young petioles are commonly sold by street vendors and eaten raw, along with salt and chilli to enhance the flavour (E. Villouta pers. comm. 2004)."

    Notes
    Bergman and Osborne (2002) report that at the end of the nineteenth century it was found that Gunnera tinctoria forms a symbioses with nitrogen fixing Cyanobacteria inside its cells. The Cyanobacteria have been classified as belonging to the genus Nostoc. There is little evidence that the host (including G. tinctoria) can survive to maturity in the absence of the cyanobacterium, and all cultivated and naturally growing plants contain the cyanobiont, irrespective of nutrient availability.
    Geographical range
    Native range: South America (Williams et al. 2005).
    Known introduced range: Australasia-Pacific Region, Europe, and North America (Law, 2003; Hickey and Osborne, 1999; and USDA-NRCS, 2005)."
    Introduction pathways to new locations
    For ornamental purposes: One of the most popular architectural" garden plants promoted throughout the 1990s for use around ponds and in damp areas was G. tinctoria" (Law, 2003).


    Local dispersal methods
    Consumption/excretion: Seeds are spread mainly by birds and along watercourses (Taranaki Regional Council, 2003).
    Management information
    Preventative measures: If possible,remove and destroy all flower heads as soon as possible, as the germination rate of the seeds is very high.

    Chemical: Best results with least bi-kill of desirable adjacent plants has been achieved by spraying with Grazon (triclopyr 600 EC) at 10 mls/litre plus a penetrant. Tordon Brushkiller (picloram & triclopyr)at 10 mls/litre plus a penetrant was also effective but was hard on nearby desirable plants (Taranaki Regional Council (TRC) and the Gunnera tinctoria specialist at the local Department of Conservation office at Stratford (DoC), New Zealand., pers.comm., June 2008).

    Cultural: Law (2003) reports that in New Zealand, extensive outreach programs have been initiated to educate the public on the dangers of this invasive. Newspaper articles and public advertisements have been created. Coastal landowners have had personal visits from Rangers who inform the landowners and invite them to participate in government sponsored control trials. The author also states that, "In cases where landowners are required to destroy G. tinctoria in a garden situation, a similarly striking, benign plant can be recommended as a replacement. In riparian situations, possible replacement plants include Carex secta or toetoe, depending on the scale of the site."

    Reproduction
    Law (2003) states that, "A single G. tinctoria may produce 250,000 seeds in a year, with the seeds being spread by water and by birds. The extensive seed bank allows G. tinctoria to easily re-colonize after mature plants have been removed. This species can also reproduce rhizomatically from fragments." Once established, vegetative growth can be rapid with rhizomes increasing by ~15cm annually (Hickey and Osborne, 1999).
    Reviewed by: Susan Timmins, Plant Ecologist (Weeds) Research, Development & Improvement. Department of Conservation, New Zealand
    Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG) with support from the Terrestrial and Freshwater Biodiversity Information System (TFBIS) Programme (Copyright statement)
    Last Modified: Thursday, 15 December 2005


ISSG Landcare Research NBII IUCN University of Auckland