- Rumex acetosella is a perennial herb that can reach 1.6 ft. (0.5 m) in height.
- Leaves are alternate, petiolate, glabrous, entire, 3-lobed, up to 1.2 in. (3 cm) long and occur in a basal rosette.
- Flowering occurs from March to November, when yellowish-green flowers (male) or reddish (female) flowers develop in clusters of a branched inflorescence at the apex of the stem. Flowers are typically drooping and have 3 petals and 3 sepals, each less than 0.04-0.06 in. (1-1.5 mm) long.
- Fruits are red achenes.
- Ecological Threat
- Rumex acetosella is native to Europe and occurs along roadsides and other disturbed areas.
Rumex acetosella L.
- ITIS (2007) lists three infraspecific taxa but notes that they are not accepted.
- Rumex acetosella ssp. angiocarpus (Murb.) Murb.
- Rumex acetosella var. pyrenaeus (Pourret) Timbal-Lagrave
- Rumex acetosella var. tenuifolius Wallr.
The following synonyms are listed in IPANE (2007):
- Acetosella acetosella (L.) Small
- Acetosella tenuifolia (Wallr.) A. Löve
- Acetosella vulgaris (Koch) Fourr.
- Rumex acetosella ssp. angiocarpus (Murb.) Murb.
- Rumex acetosella var. pyrenaeus (Pourret) Timbal-Lagrave
- Rumex acetosella var. tenuifolius Wallr.
- Rumex angiocarpus Murb.
- Rumex tenuifolius (Wallr.) A. Löve
Rumex acetosella’s common names include sheep sorrel, field sorrel, and red sorrel.
DESCRIPTION AND DIAGNOSTIC CHARACTERISTICS
Leaves are 2-10 cm (0.8 to 4 in.) long and 1-2 cm (0.4 to 0.8 in) wide. Most leaves occur in a basal rosette but there are often cauline leaves. Basal leaves are alternate and lobed, with the terminal lobe narrowly lanceolate (2-12 mm (0.08-0.5 in.) in length ) and the lateral lobes much smaller and triangular (sagittate or hastate leaf bases). Basal leaves are approximately 2.5-7.6 cm (1-3 in.) long, petiolate, and glabrous. Cauline leaves are alternate, usually without lobes, and with no or small petioles. All leaves have a thin membranous sheath (ocrea) surrounding the stem at the point of leaf petiole attachment. The sagittate leaves and distinct reddish tinge color are useful distinguishing characteristics.
Roots are yellowish and range from very fine (<0.5mm) to large (>3mm) in diameter (pers. obs.).
Flowering stalks can be up to half as long as the total plant length. Flowers are morphologically distinct between male and female plants. Male flowers are yellow and female flowers are reddish ). Flowers are nodding on short, jointed pedicels. Male flowers have obovate inner tepals measuring 1.5-2 mm (0.06-0.08 in.) in size. Female flowers have tepals that are broadly ovate in shape.
The shiny, golden brown fruits are achenes, and are 3-angled and measure approximately 1.5 mm (0.06 in.) in size. In New England fruits are present on the plant from June-October.
Cotyledons are hairless, oblong, and up to 10 mm (0.4 in.) in length. Cotyledons and young leaves do not have smooth surfaces. Young leaves are oblong; basal sagittate leaves develop later .
There are 200 species in the genus. Rumex acetosa L. (garden sorrel) is similar but of larger stature than R. acetosella, (Delmas 1993). In the U.S. R. acetosa is reported from Connecticut, Massachusetts, Maine, Michigan, Minnesota, Montana, New Hampshire, New Jersey, New York, Oregon, Pennsylvania, Vermont, Washington, Wisconsin, and Wyoming.
Biomass removal, especially removing the roots is key to success. Seedlings, root fragments left underground, and any plant parts left above ground can be a source of new plants. Its roots can grow to depths of 1.5 m (5 ft.) deep, making it difficult to control and manage using manual and/or mechanical techniques. This species appears susceptible to glyphosate and herbicides containing dicamba.
HABITAT & RANGE
Rumex acetosella is native to most of Europe, Russia, the Middle East and northern Africa. R. acetosella is naturalized in New Zealand, Greenland, western South America, the southern tip of Africa, Iceland (GBIF 2007) and the US. In the U.S. it occurs in all 50 states. APWG (2007) lists it as invasive in Arizona, Connecticut, Hawaii, New York, Oregon, Tennessee, Virginia, Washington, Wisconsin, and, West Virginia. Rumex acetosella has been named a noxious weed in Iowa and is banned from import and sale in Connecticut (USDA PLANTS). This species is found in a wide range of habitats but especially fields and disturbed places. It is common in floodplains , oak woodlands, and yellow pine forests.
Rumex acetosella occurs often in grassland or other open habitat. In western Washington it is found in areas dominated by Salix scouleriana; it also grows with Fragaria virginiana, Holcus lanatus, Trifolium repens, Rumex crispus, and Juncus effusus (Fonda 1974). In Oregon R. acetosella is commonly associated with Bromus tectorum. In Connecticut it occurs in a postagricultural Schizachyrium scoparium grassland with Agrostis alba and Carex pensylvanica (Niering and Dreyer 1989). In New Jersey it grows with Solidago canadensis (Carson and Picket 1990). It grows in southern Appalachian grassy bald communities dominated by Danthonia compressa and growing with Rubus canadensis, Vaccinium pallidum, and Viola spp. (Lindsay et al. 1979, Mark 1958). In Indiana, R. acetosella occurs with Schizachyrium scoparium, Celtis occidentalis, and Equisetum laevigatum (Strait and Jackson 1986). In Montana and Wyoming, it grows in alpine tundra (Weaver et al. 1990). In South Carolina R. acetosella grows in a disturbed Andropogon virginicus (Golley 1965). In California it has been noted growing in a freshwater marsh with Festuca arundinacea, Carex spp., Typha angustifolia (Fiedler and Leidy 1987). In California R. acetosella is common in annual grassland, montane meadow, and perennial bunchgrass communities. Associates include Bromus rigidus, B. hordeaceus, Aira caryophyllea, Poa pratense, P. nevadensis, Carduus pycnocephalus, Avena fatua, and Lolium multiflorum (Boyd et al. 1993, Davis and Sherman 1992, Fiedler and Leidy 1987, McBride et al 1991). At Point Reyes National Seashore, California, R. acetosella occurs in a coastal grassland community with coast rock cress Arabis blepharophylla, Toxicodendron diversilobum, Berberis pinnata, and Chorizanthe valida (Clark and Fellers 1986, Davis and Sherman 1992).
Rumex acetosella can also be found in forested areas, including the following. In Pennsylvania R. acetosella occurs in Pinus strobus-Danthonia spicata communities with Solidago canadensis, Epilobium angustifolium, Lysimachia quadrifolia, Claytonia virginica, Erythronium americanum, Oxalis montana, and Viola spp. (Auchmoody and Walters 1988, Kolb et al. 1990, Walters and Auchmoody 1989). In Alberta, R. acetosella is a member of an 80-year-old Picea glauca-Pinus banksiana-Pleurozium spp. community (Fyles 1989). In Idaho R. acetosella occurs with Abies grandis, Asarum caudatum, Pachistima myrsinites, and Physocarpus malvaceus (Green and Jensen 1991, Leege and Godbolt 1985, Leege et al. 1981, Zimmerman and Neunschwander 1984). In California R. acetosella occurs in Sequoia sempervirens, Pseudotsuga menziesii, Quercus garryana habitats (Gardner 1958, Krueger and Donart 1974, Sugihara et al. 1987). In the foothills of the Sierra Nevada and Coast Ranges, California, R. acetosella grows under Quercus douglasii (Holland 1980).
IMPACTS AND THREATS POSED BY Rumex acetosella
It can form colonies at least 10 to 30 feet in diameter to the exclusion of other plants.
BIOLOGY AND ECOLOGY
Light and Temperature
R. acetosella grows under a variety of conditions but it appears to prefer open areas (Parker 1995). It easily tolerates freezing temperatures during the winters of northern states.
Soil conditions (pH, moisture, texture, nutrients)
Rumex acetosella prefers areas with very poor, acid soil with low nitrogen. It does not grow well in calcareous soils. In one study, peak density was observed under low nitrogen (Tilman 1988). In West Virginia R. acetosella grows well in all but limestone regions (Strausbaugh and Core 1977).
Flooding and/or Drought Tolerance
Plants reproduce both by seed and vegetatively. Individuals often form massive populations with one or few genets.
|Georgia||Mar-Jun||(Wofford 1989, cited in Esser 1995)|
|Tennessee||Mar-Jun||(Wofford 1989, cited in Esser 1995)|
|Virginia||Mar-Jun||(Wofford 1989, cited in Esser 1995)|
|North Carolina||Mar-July||(Radford et al. 1968 and Wofford 1989, both in Esser 1995)|
|South Carolina||Mar-July||(Radford et al. 1968 and Wofford 1989, both in Esser 1995)|
|Kansas||Apr-July||(Bare 1979, cited in Esser 1995)|
|Great Plains||Apr-Aug||(Great Plains Flora Association 1986, cited in Esser 1995)|
|North Dakota||May-Jun||(Dittberner et al. 1983, cited in Esser 1995)|
|Montana||May-Aug||(Dittberner et al. 1983, cited in Esser 1995)|
|Idaho||May-Sept||(Fitzsimmons and Burrill 1993)|
|Oregon||May-Sept||(Fitzsimmons and Burrill 1993)|
|Washington||May-Sept||(Fitzsimmons and Burrill 1993)|
|West Virginia||May-Sept||(Strausbaugh and Core 1977, cited in Esser 1995)|
R. acetosella spreads rapidly by producing new plants from adventitious stem buds on the roots. Those buds are usually found in the top 20 cm (8 in.) of the soil (Kiltz 1930).
Sheep sorrel invades disturbed sites and may move onto undisturbed sites. It colonizes rapidly by seed and may persist for 15 to 20 years (Escarre et al. 1994). Competition from other species on good soils may reduce its abundance (Fitzsimmons and Burrill 1993).
In 2006 in the Presidio of San Francisco a greenhouse study was conducted to evaluate the survival of 5 in. (12.7 cm) R. acetosella root fragments of varying thickness when buried at various depths. As time passed more deeply buried roots produced leaves. After one month all roots left on the surface except for the thickest roots had produced leaves. After two months all roots buried at two inches also produced leaves. After three months the thickest roots buried at four inches also produced leaves. No plants emerged after three months. No roots buried at 6 inches or deeper produced leaves (Frey et al. 2008).
Seed Dispersal, Seed Banking
The seeds are dispersed by both wind and insects. The shiny, 3-angled achenes are mahogany red and 1.6 mm (.063 in.) or less long. Sheep sorrel has a persistent seedbank and may be present as seeds even when there are no growing plants. These seeds germinate following disturbance (Del Tredici 1977, Fyles 1989, Granstom and Schimmel 1993, Livingston and Allessio 1968). Buried seed remains viable in the soil for extended periods (Fitzsimmons and Burrill 1993).
R. acetosella provides poor forage for livestock but is grown and sold for human consumption.
Good control of Rumex acetosella is complicated because it reproduces and can be spread both by seed and vegetatively. Shoot removal appears to only slow or temporarily inhibit seeding. This strategy also slows vegetative spread (Fitzsimmons and Burrill 1993). The removal of shoots without root removal appears to stimulate shoot growth, leading to greater percent cover than before shoot removal (Frey et al. 2008).
Potential for Restoration of Invaded Sites
Impacts from mechanical control techniques can create highly disturbed areas. This disturbance may or may not be desired, depending on the nature of the invaded plant community. If the plant community depends on disturbance (such as coastal dunes) then this techniques may be suitable. If, however, major disturbance would result in a weed flush or otherwise disrupt the community then this techniques may be unsuitable
After R. acetosella removal restoration success is high. There are no apparent chemical or physical legacy effects of the invasion.
Prevention and Early Detection
As with all unwanted species early detection and prevention are the most cost effective strategies to protect native habitats from invasive species.
Manual and Mechanical Control
Removing as much of the shallow roots as possible is the most effective method to reduce plant abundance. On a small scale this can be done effectively with a pick or shovel (Frey et al. 2008). After clearing an area, reduce resprouting and seed germination by applying a thick mulch. (Sunset 1998).
Fitzsimmons and Burrill (1993) found that roots were exhausted by repeated cultivation during dry weather.
In 2007 in the Presidio of San Francisco large patches of dense R. acetosella were selected. Seven techniques were tested: 1) use a propane torch to wilt the leaves, 2) use a hula hoe to cut plants just below the soil surface and leave on site, 3) without digging up plants, pull and remove from the site, 4) with a hand-pick, remove from the site as much of the root and shoot as possible, 5) cover vegetation with a black, semipermeable landscape fabric for six months, 6) remove 3 inches of soil, sift through a screen, and return to the plot, 7) remove 6 inches of soil, sift through a screen, and return to the plot.
Time required varied dramatically by treatment. The techniques that removed root biomass (pick and digging) reduced percent cover of R. acetosella. In sand, the pull method and 6 inch dig still showed a reduction in percent cover one year after implementation. In serpentine no treatments showed an effect after one year but the 3 inch dig treatment reduced cover up until the third quarter. Results suggest that the flame treatment is the least effective method (Frey et al. 2008).
The oxalic acid in R. acetosella causes dermatitis in some animals and there have been reports that horses and sheep have been poisoned from eating large quantities of this plant .
R. acetosella is grazed by sheep and cattle (Humphrey 1955), and mule deer (Krueger and Donart 1974, Nixon et al. 1970). Grouse eat sheep sorrel seed (Hungerford 1951, Hungerford 1957, Schmidt 1936, and Swenson 1985).
There is no evidence of grazing being tried as a control method.
No studies were found that used prescribed fire as a tool to control R. acetosella. However, some information is available about this species’ reaction to fire. Esser (1995) describes many studies that mention R. acetosella and its response to fire (Boyd et al. 1993, Del Tredici 1977, Fyles 1989, Granstrom and Schimmel 1993, Hall 1955, Leege and Godbolt 1985, MacLean and Wein 1977, Maltby et al. 1990, Merrill et al. 1980, Minore et al. 1979, Niering and Dreyer 1989). In general, R. acetosella was less than 5% before the fires and after the fires. However, the rate of increase and/or establishment was generally greater than that observed in the controls.
A 50% Rodeo solution painted directly on the leaves of R. acetosella in a coastal dune restoration project in the Presidio of San Francisco reduced R. acetosella from 42±2 to 7±6 percent cover after six months (unpublished data).
Oregon State University (1998) recommends dicamba for R. acetosella. They suggest 0.5 pounds dicamba per acre . They also recommend that dicamba be applied when red sorrel has new foliage in the late fall, winter, or early spring. They report that spring application controls spring-germinating seedlings better than sprays applied earlier and that this treatment will prevent the setting of seed on surviving plants (Oregon State University 1998).
Sunset (1998) recommends using an herbicide containing dicamba or spot treating with glyphosate.
Fitzsimmons and Burrill (1993) report that several herbicides can selectively control sheep sorrel. They do not list them but refer the reader to the annually published Pacific Northwest Weed Control Handbook. This document, now called the PNW Weed Management Handbook can be found at http://weeds.ippc.orst.edu/pnw/weeds. On 6/6/2007 only Dicamba was recommended. The recommended time to apply was “when red sorrel has new foliage, usually November 15 to March 15. Spring application controls spring-germinating seedlings better than sprays applied earlier.” They also note that the recommended treatment will kill seedlings and most mature plants and that it will prevent seed set in those plants that do survive (Oregon State University 2007).
Although control with hexazinone (a triazine herbicide) showed promising preliminary results future study revealed that sheep sorrel grew and produced a large number of seeds (McCully et al. 1991).
In Pennsylvania in a Solidago spp. and Aster spp. community that was plowed, disked, and prometone-treated, sheep sorrel was dominant in 1- and 3-year-old plots (Medve 1984).
No biocontrols known to be released for this species.
EXAMPLES OF MANAGEMENT PROGRAMS FOR Rumex acetosella
Where Rumex acetosella control is a regular part of restoration activities in the Presidio of San Francisco repeated removal multiple times per year has proven successful.
Monitoring the spread of this species and detecting it early are keys to success. Also, monitoring is necessary to detect any changes in condition of the desired community, and to see what the response of the weed and your community is in response to your management treatments.
- Non-chemical control techniques.
- How much biomass needs to be removed to prevent flowering?
- How many times and with what frequency does shoot removal result in death?
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