**Rumex acetosella L.. (Polygonaceae)**

**Sheep Sorrel, Red Sorrel**

**Description**. Dioecious or polygamous perennials, colonial, from
slender rhizomes. Stems 1 to 5 dm tall, erect, simple, glabrous. Leaves
alternate, the stipules modified into prominent sheaths, lower leaves
petiolate, 2 to 6 cm long, 1 to 2.5 cm wide, blade shape variable,
linear to ovate, hastate to sagittate, the terminal lobe much longer
than the basal lobes, acute to obtuse, margins entire, the cauline
leaves reduced upwards, short-petiolate to sessile, the blades with 1 or
no lobes, upper ones sheath-like. Inflorescence 5 to 15 cm long, an open
panicle, the branches slender, ascending, glabrous, yellowish to
reddish. Flowers unisexual, in clusters, sessile to pedicellate, often
somewhat pendulous, perianth parts in two whorls of 3 each, 0.5 to 2 mm
long, greenish to reddish, fused near the base, the inner ones expanding
and somewhat enclosing the achene in fruit; staminate flowers with 6
stamens; pistillate flowers with 1 superior ovary, the styles 3, the
ovary 3-angled, with 1 locule. Fruit a 3-angled achene, 1-2.5 mm long,
yellowish to brownish red. In California, flowering from March to July.
(Gleason and Cronquist 1991, Hickman 1993, Kaul 1986, Munz 1959, Welsh
1984).

**Geographic** **distribution**. A native of Eurasia, sheep sorrel has
become naturalized throughout North America, South America, Australia,
New Zealand, Japan, southern Africa and Hawaii (Clapham et al. 1982,
Fernald 1950, Gleason and Cronquist 1991, Gobbi 1995, Kaul 1986, Munz
1959, Ohwi 1965, Wagner et al. 1990, Webb et al. 1988).

Sheep sorrel was first reported from California (without locality) by
Watson (1880), but probably was widely distributed prior to the late
1800s (Jepson 1914, Robbins 1940). It has been reported only from Santa
Cruz and Santa Rosa islands (Junk et al. 1997) but occurs widely
throughout most mainland California counties (Anonymous 1998, Hickman
1993).

**Reproductive and vegetative biology**. Sheep sorrel is dioecious,
pollinated by wind, but occasionally visited (for pollen) by insects
(Proctor et al. 1996, Richards 1986). Seeds may remain dormant for up to
20 years (Tsuyuzaki and Kanda 1996).

Although sheep sorrel represents a polyploid complex (2x, 4x, 6x, and
8x) worldwide, chromosome number does not appear related to ecological
distribution nor does it have an effect on sex ratios (Love 1944,
Richards 1986). However, because of clonal growth, sex ratios in some
populations are often skewed toward one of the two sexes (Houssard et
al. 1994, Houssard and Escarre 1995, Richards 1986). Staminate plants
are generally shorter, and flower and senesce early, relative to
pistillate plants. Pistillate plants are usually larger and have
relatively higher reproductive effort, based on flower number. However,
Putwain and Harper (1972) showed that the rarer sex often had higher
productivity and reproductive capacity, measured either as pollen or
seed output. In most cases, ramet growth from root buds contributed much
more to to population expansion than annual seed output and recruitment.

Initial establishment of *Rumex* *acetosella* by seed is relatively
rare, but appears favored by reduced competition (at least from grasses)
and relatively low nutrient levels (Harper 1977, Mamolos et al. 1995,
Putwain et al. 1968). Sheep sorrel is a non-mycorrhizal species, and can
expand in the absence of competitive mycorrhizal species after fungicide
treatment on nutrient-poor soils (Newsham et al. 1995). Ecotypic
variation, combined with phenotypic plasticity, can result in different
genotypes dominanting stages of old-field succession, resulting in
long-term persistence as a species (Escarre et al. 1994, Houssard and
Escarre 1995, Korpelainen 1993).

**Ecological distribution**. Sheep sorrel is generally found on moist
soils of waste places, open, disturbed sites, or vernally moist meadows
and grasslands (Fernald 1950, Gleason and Cronquist 1991, Kaul 1986,
Munz 1959, Welsh 1984). *Rumex acetosella* has also been reported from
coastal prairie and costal scrub communities (Heady et al. 1988). In
South America, it has been reported as a common invasive after grassland
fires (Gobbi 1995).

**Weed status.** Sheep sorrel is not considered a noxious weed in
agricultural or horticultural practice, at least at a global level (not
listed by Holm et al. 1977), nor is it considered a noxious weed by the
State Dept. of Food and Agriculture (Anonymous 1996). However, it is
listed for the United States in Lorenzi and Jeffery (1987) and is
considered a noxious weed in Australia (Lemerle 1996).

**Microbial pathogens**. No literature was found that reported *Rumex
acetosella* as a host to fungal pathogens. It has been reported as a
host to the tomato spotted leaf virus (Bitterlich and McDonald 1993).
Migliore et al (1997) documented the uptake of sulphadimethoxine, an
antimicrobial compound used in the livestock industry, in sheep sorrel
and the potential for ingestion by cattle.

**Insect pathogens**. No literature was found thar reported insects
detrimental to *Rumex acetosella*.

**Herbicide control**. Harper (1977) reported that sheep sorrel in
experimental plots was resistant to paraquat, but effectively controlled
by 2,4-D and Tordon. No other literature was found that specifically
addressed herbicide control of *Rumex* *acetosella*. Lorenzi and Jeffery
(1987), however, recommended mechanical removal or spot treatment with
2,4-D plus dicamba for low density infestations and glyphosate for large
infested areas.

**Literature Cited**

Anonymous. 1996. Exotic pest plants of greatest ecological concern in
California as of August 1996. California Exotic Pest Plant Council. 8
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Anonymous. 1998. USDA Plants Database, Baton Rouge, LA. URL =
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Escarre, J., C. Houssard, and J. Thompson. 1994. An experimental study
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