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   Rumex obtusifolius (herb)     
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         Interim profile, incomplete information
    Taxonomic name: Rumex obtusifolius L.
    Synonyms: Rumex obtusifolius var. subalpinus Schur [= Rumex obtusifolius subsp. subalpinus], Rumex sylvestris var. transiens Simonk. [= Rumex obtusifolius subsp. transiens], Rumex sylvestris Wallr. [= Rumex obtusifolius subsp. silvestris]
    Common names: acedera de hojas obtusas (Spanish), acedera obtusifolia (Spanish), bijuaca (Spanish), bitter dock (English), bluntleaf dock (English), broadleaf dock (English), broad-leaved dock (English), celery seed (English), dock (English), dun ye suan mo (Chinese), engorda puercos (Spanish), ezo-no-gishi-gishi (Japanese), labaca (Portuguese), labaça-de-vaca-amarga (Portuguese), lengua de vaca (Spanish), língua-de-vaca-amarga (Portuguese), oseille (French), parelle (French), patience à feuilles (French), patience sauvage (French), romaza de hojas grandes (Spanish), romaza vulgar (Spanish), rumex à feuilles obtuses (French), stumpfblättriger Ampfer (German), vinagrillo (Spanish), yerba mulata (Spanish)
    Organism type: herb
    Broad-leaved dock (Rumex obtusifolius) is a problematic weed throughout its native and introduced range. It invades a wide variety of habitats in the Sub-Antarctic region including areas dominated by native plant species. It is also a major problem in pastures. Current management strategies include chemical and mechanical control, although studies investigating biological control agents are ongoing.
    Description
    Rumex obtusifolius is an erect perennial herb that grows up to 40-150cm tall. Plants usually consist of a basal rosette of leaves and a large, fleshy taproot. The leaves develop individually as tightly rolled leaf spikes. These spikes unfurl about a week after initiation, the leaves going on to expand to a maximum size of 40 cm long by 20 cm wide (I.P. Keary, pers. obs., in Grossrieder & Keary, 2004). Leaf area and stem length are very plastic in response to environmental cues, especially light. Developmental rates and overall plant size also vary a great deal between individuals grown in similar conditions (I.P. Keary, pers. obs., in Grossrieder & Keary, 2004). During flowering, a tall spike up to 150 cm in height is produced which bears the inflorescence. Following flowering, the plant undergoes defoliation. This can result in a complete loss of leaves for up to two months (Grossrieder & Keary, 2004).
    Similar Species
    Rumex hydrolapathum

    More
    Occurs in:
    agricultural areas, riparian zones, ruderal/disturbed
    Habitat description
    Historically Rumex obtusifolius has been particularly associated with disturbed ground, short-term leys and badly managed grassland but is now a widespread problem across many farms, including organic farms, in Europe. Its adaptation to growth on naturally disturbed environments, such as river banks and dunes, makes it ideally suited to colonising gaps and wasteland produced by human activity (Grossrieder & Keary 2004). In addition to a wide climatic tolerance (see Geographical Range sub-heading), Cavers & Harper showed that the plant is capable of growing from seed on a wide range of soils, with only the most acid soils, such as those from peat bogs, inhibiting growth (in Grossrieder & Keary 2004).

    In the Sub-Antarctic region, where it has been introduced, R. obtusifolius tends to dominate disturbed land such as soil-slips and depressions and man-modified sites (Dean et al. 1994). In general it invades a variety of habitats including: footpaths, landslides, depression left by boulders, old settlements/cultivations, rivers, beach lands, bird burrows and nests, cleared plots, marsh land and undisturbed/native vegetation (Dean et al. 1994). R. obtusifolius is naturalised in Hawai'i in relatively mesic, disturbed areas; sometimes present in areas dominated by native species, usually found at altitudes of between 600 and 1470 meters (Wagner et al. 1999, in PIER 2007). This species is present in New Zealand near human habitations; it is also common to abundant in pastures, river banks, open moist places and around stockyards, cowsheds and other places with high nitrogen levels (Webb et al. 1988, in PIER 2007).

    General impacts
    Rumex obtusifolius is a major weed of gardens and arable land (Webb et al., 1988 in PIER, 2007). The Global Compendium of Weeds (2007) lists R. obtusifolius as an agricultural, environmental and garden weed.

    Broad-leaved dock is a pernicious weed throughout its native and introduced range. It invades agricultural land, particularly heavily managed pasture land. In the grassland systems of Switzerland R. obtusifolius is a major problem. As a weed of pastures and meadows, the main impact of this plant is to reduce the value of infested land as grazing for livestock. R. obtusifolius is only 65% as valuable as grass as grazing material because of a combination of reduced palatability (and therefore grazing levels) and reduced digestibility (Courtney & Johnson, 1978 in Grossrieder & Keary, 2004). It also contains oxalic acid which may be poisonous to livestock.

    Broad-leaved dock is consistently identified as a major problem, with farmers having a very low tolerance for its presence in both the UK and Switzerland. Infestation of grassland by this weed is consistently cited by organic farmers as a particular cause for concern, although both species prove difficult to control even when chemical interventions are allowed. Established plants of both species possess a large and persistent taproot that contains a large reserve of resources. This allows individual plants to tolerate repeated defoliation (Grossrieder & Keary, 2004).

    Mature plants also suppress the grass yield of pasture. Oswald and Haggar (in Grossrieder & Keary, 2004) found that increasing ground cover by Rumex reduced grass yields, as did increasing Rumex density. According to Courtney (Grossrieder & Keary, 2004), this effect is greater when the pasture is cut 3 to 4 times a year (a 70% reduction in grass yield) rather than 5 to 7 times a year (a 16% reduction).

    These problems are exacerbated by the ability of R. obtusifolius to exploit nitrogen efficiently. Niggli et al.(in Grossrieder & Keary, 2004) found that increases in fertilizer had no negative effect on the weed. Jeangros & Nösberger (in Grossrieder & Keary, 2004) found that higher levels of nitrogen fertilization were of net benefit to R. obtusifolius seedling growth, particularly when shoot competition with the sward was reduced.

    Additionally, plants can host high diversity of plant pathogens and invertebrate pests that may affect surrounding plants (Martinkova et al., 2009 and references therein).

    Uses
    Rumex obtusifolius is sometimes used for medicinal purposes (USDA-NRCS 2008). It is used in folklore medicine, and has been used as an antidote to nettle, depurative, astringent laxative and for the treatment of sores, blisters, burns, cancer and tumours (Dr Duke’s Phytochemical and Ethnobotanical Databases, 2009 in Harshaw et al., 2010). Studies of the plant have revealed the presence of anthracene derivatives, flavonoids, procyanidins, oxalic acid. It also has antioxidant and antibacterial activities (Harshaw et al., 2010).
    Notes
    Subspecies of Rumex obtusifolius include: Rumex obtusifolius subsp. obtusifolius, Rumex obtusifolius subsp. silvestris, Rumex obtusifolius subsp. subalpinus, Rumex obtusifolius subsp. transiens (USDA-NRCS 2008).
    Geographical range
    Native range: Europe (Wagner et al. 1999, in PIER 2007). If enough water is available R. obtusifolius appears to have few climatic limits on its distribution, occurring naturally from north of the Arctic Circle in Norway southwards through the rest of Europe, with the exception of the Mediterranean (Grossrieder & Keary 2004).
    Known introduced range: The plant has also been introduced to, and is now widely established in, South America, Australia and Japan and is a weed throughout its range (Grossrieder & Keary 2004).
    Local dispersal methods
    Natural dispersal (local): Rumex obtusifolius fruits are lightweight and moved long distances by wind. They are also spread by moving water and by adhering with mud to clothes, machinery and the fur, feathers and feet of other animals (Holm et al. 1977, in PIER 2007).
    Transportation of habitat material (local): Rumex obtusifolius is dispersed via dung and mud (Dean et al. 1994).
    Water currents: Rumex obtusifolius is dispersed via water (Dean et al. 1994).
    Management information
    The long-term goal of control measures against Rumex is to reduce build-up of seeds and weaken their regrowth capacity by removing or destroying their above- and below-ground biomass.

    Chemical: R. crispus is sensitive to many herbicides, especially synthetic auxins (MCPA, 2,4-D, dicamba, dichlorprop-P, fluroxypyr, etc.) and many sulphonylureas (tribenuron, thifensulfuron, amidosulfuron, etc.) (Jursík et al., 2008). Thifensulfuron can be used for dock management in perennial legume stands, good efficacy is also shown by asulam, which is recommended for local application only, due to lower selectivity (Jursík et al., 2008).
    Public concern about pesticides in the environment has led to greater demand for non-chemical control methods and the development of mechanical and cultural measures to control plants (Zaller, 2004).

    Mechanical: If herbicides are not used, the best option is control via manual removal or destruction of plants. This can be achieved via hand weeding, although is only suggested for use in small areas as it is labour intensive (Besson et al., 1982 in Grossrieder & Keary, 2004). It is necessary to remove the tap root to a depth of 20 cm in order to prevent regrowth (Zaller, 2004). Recent developments in mechanical control include a motor-driven dock pulling machine which can pull up about 600 Rumex plants per hour (Pötsch, 2003 in Zaller, 2004).

    Well developed R. obtusifolis plants can be difficult to control with cutting or grazing. Because of rapid replenishment of carbohydrate in roots, plants require repeated defoliation over a period of several years, which can be achieved by frequent cutting or grazing (Stilmant et al., 2010). However, increased cutting frequencies may increase disturbance and offer opportunities for new seedlings to germinate and establish (Grossrieder & Keary, 2004).

    Grazing: Grazing by sheep has been proposed as an alternative to manual removal, but may not be as effective as hand pulling (Van Middelkoop et al. 2005 in Van Evert et al., 2009). While Rumex species are unpalatable to many livestock, they are a favourite of deer (Cavers & Harper, 1965). More studies should focus on mixed grazing (e.g. cows and goats) to control Rumex (Zaller, 2004).

    Cultural: Mechanical removal can be combined with grassland renewal and rotation with a grain crop (Van Middelkoop et al., 2005 in Van Evert et al., 2005). Some authors have suggested combating the problem of regrowth by leaving the ground as a bare fallow following a rotary cultivation in spring, so that the unearthed root fragments are killed by desiccation (in Grossrieder & Keary 2004). As Rumex seedlings require high light, control through shading may be effective (Zaller, 2004).

    Biological: Numerous insects and fungi have been proposed as biological control agents for R. obtusifolius. The most thoroughly studied organisms are the beetle Gastrophysa viridula and the rust fungus Uromyces rumicis. Studies with Coleoptera have found reductions in seed production, regeneration, and leaf and shoot growth. Similarly studies with fungi have found similar effects and increased root rotting. However no agent has shown to be sufficiently effective against R. obtusifolius. Studies have shown that combinations of herbivorous beetles and fungi may produce more effective results. Efficacy of biological control tends to be more effective when plants are already stressed by environmental conditions (Reviewed by Zaller, 2004).

    Nutrition
    Rumex obtusifolius is a C3 plant. It strongly competes with other, agriculturally valuable species for resources (nutrients, water, space and light) (Ref). It can survive on low nutrient soils (Martinkova et al., 2009). A recent study found that R. obtusifolius increases its above ground biomass in response to drought, causing it to comprise 80% of total community biomass. It is much less affected by drought than other plant species due to higher water use efficiency and change in nitrogen acquisition patterns. This gives R. obtusifolius a competitive advantage over other species, which may be particularly pronounced in future drier climatic conditions (Gilgen et al., 2010).
    Reproduction
    Rumex obtusifolius reproduces via production of seeds enclosed in a fruit (Holm et al., 1977 in PIER, 2007). The seeds can remain viable in the soil for many years. A very small number of seeds retain viability after 80 years burial and around a third remain viable after 20 years (Grossrieder & Keary, 2004). The persistence of its seeds, combined with the longevity and seed-producing capacity of the mature plants, means that R. obtusifolius is able to make a large contribution to the soilborne seed bank of any areas it infests. This extends the problems presented by the weed beyond the life span of the current mature plants until the seed bank is exhausted (Grossrieder & Keary, 2004).

    R. obtusifolius can also reproduce clonally. If the taproot is split during cultivation, the fragments can regenerate to produce new plants (Grossrieder & Keary, 2004). Work by Pino et al. has shown that only the underground stem above the root collar can produce such regrowth. Despite this finding, it is still common practice to remove at least the upper 9 cm of the root system to prevent regrowth (in Grossrieder & Keary, 2004). The underground stem system can also split naturally with age and secondary root systems develop, allowing the plant to spread clonally in closed habitats (Grossrieder & Keary, 2004).

    Lifecycle stages
    The number of seeds produced is highly variable, from about a hundred to a maximum of 60,000 to 80,000. The seeds are small and highly dispersive. They are capable of being moved long distances by wind and animals and can be transported both on the coats of livestock and via their dung. However, the majority of the seeds tend to be found clumped close to the parent plant. Flowering seldom takes place in the first year of growth (although it has been recorded as early as 9 weeks after germination), thereafter the plant normally flowers once a year, but twice is not uncommon (Grossrieder & Keary, 2004).

    Rumex obtusifolius is a perennial plant, meaning it persists for several seasons. A study investigating R. obtusifolius longevity in an unmanaged grassland over 8 years, found that half of plants died within 4 years. 4% of plants survived the whole 8 years. In general winter mortality was greater than summer mortality. Plants decreased in size before mortality. Below ground competition and water deficiency are proposed reasons for most mortalities (Martinkova et al., 2009).

    Principal sources:
    Grossrieder, M. & Keary, I.P. 2004. The potential for the biological control of Rumex obtusifolius and Rumex crispus using insects in organic farming, with particular reference to Switzerland. Biocontrol News and Information, 25(3): 65-79.
    Zaller, J.G. 2004. Ecology and non-chemical control of Rumex crispus and R. obtusifolius (Polygonaceae): a review. Weed Research, 44: 414-432.
    Compiled by: Interim profile: IUCN SSC Invasive Species Specialist Group (ISSG) with support from the EU-funded South Atlantic Invasive Species project, coordinated by the Royal Society for the Protection of Birds (RSPB)
    Updates with support from the Overseas Territories Environmental Programme (OTEP) project XOT603, a joint project with the Cayman Islands Government - Department of Environment
    Last Modified: Monday, 6 September 2010


ISSG Landcare Research NBII IUCN University of Auckland