Rumex acetosa L., Common Sorrel
Account Summary
Native. Extremely common and widespread, locally abundant. Eurosiberian boreo-temperate, but widely naturalised in both hemispheres and now circumpolar.
1881; Stewart, S.A.; Co Fermanagh.
Throughout the year.
Growth form and preferred habitats
This is a very common, variable, phenotypically plastic, sometimes abundant wintergreen, tufted, semi-rosette perennial of established, unimproved grasslands on a wide range of moist to dry soils in a huge variety of habitat situations. Like the smaller R. acetosella, leaves are characterised by a sour, acid taste, in spring sometimes described as refreshing and therefore long used in diet and folk medicine (see below). In Fermanagh, as in most of the rest of B & I, Common Sorrel is almost ubiquitous in old, established grassy places with mildly acid to neutral, impoverished to moderately fertile, base-poor to base-rich soils.
It is successful on account of having both wide, easily met ecological tolerances, plus physiological and biological characteristics that allow it to cohabit with grasses and many herb species in sub-optimal meadow and pasture environments. These conditions allow moderate levels of competitive interaction to develop, yet they prevent sustained, vigorous plant growth by any plant species (Grime et al. 1988). Given sufficient time and continuing, but moderate levels of varying disturbance, such conditions encourage the eventual development of species-rich grassland vegetation. Apart from evading strong competition in fertile soils, R. acetosa chiefly avoids environmental extremes such as aquatic, regularly flooded, strongly acid or deeply shaded conditions.
Like other Dock species, it contains toxic levels of bitter-tasting oxalates which make livestock avoid it, and it can thus survive fairly high levels of grazing. R. acetosa is morphologically flexible and tolerates mowing very well. Its rootstock can also survive moderate degrees of trampling, fire and other forms of disturbance which limit the plants' growth, reproduction and competition.
In addition to agricultural grasslands, R. acetosa is commonly found on track-sides, openings in woods, open areas on roadside verges, waste ground and cliffs.
Variation
R. acetosa has wide ecological tolerances and a matching wide geographical amplitude based on an extensive range of both phenotypic and genetic variation. Much of the phenotypic response to the environment is continuous variation and it is therefore unsurprising that taxonomic treatment of it has varied greatly over the years (Tutin et al. 1993; Jonsell et al. 2000). R. acetosa is regarded as a polymorphic species, and in Flora Europaea, Tutin et al. (1993) support three European subspecies. However, in their recent critical Flora of Great Britain and Ireland, Sell & Murrell (2018) transfer R. acetosa to a genus on its own, naming it Acetosa pratensis Mill., within which they recognise four subspecies.
The additional form in the latter is subsp. biformis (Lange) P.D. Sell, which is small (up to 20 (or exceptionally 30) cm), and has rather thick, succulent leaves and papillae ± confined to the basal margin of leaves. It is said to be native on sea cliffs in Cornwall, Cardiganshire and Co Clare (Sell & Murrell 2018). The authors of Flora Europaea believed subsp. biformis could not be satisfactorily separated from robust plants of subsp. acetosa, and it is very similar in description to subsp. hibernica (Rech. f.) P.D. Sell, except the latter has papillae and very short hairs on all vegetative parts.
Hybrids
Unlike the Dock species of the subgenus Rumex which cross frequently, there are no hybrids involving either R. acetosa or R. acetosella (Stace et al. 2015).
Fermanagh occurrence
In Fermanagh, by 2010, Common Sorrel was recorded well over 1,150 times (more than 300 records ahead of the next Rumex species, R. obtusifolius (Broad-leaved Dock)). It has been recorded in 467 Fermanagh tetrads, 88.5% of those in the VC, thus making it the 20th most widespread species in tetrad terms in the 35-year survey (1975-2010) carried out by Robert Northridge and the current author. Despite the high frequency of R. acetosa finds in Fermanagh, we feel that if we searched long enough it might well be possible to record it in every single tetrad in the county!
Reproduction
R. acetosa might be even more common if it were not for the fact that individual plants are not long-lived. Also, unlike R. acetosella, this species has only limited powers of vegetative reproduction, plants only producing daughter rosettes for recovery purposes after they survive moderate levels of disturbance.
Although it has separate male and female plants (ie it is dioecious), seed (achenes) are copiously set by the large female inflorescences. Flowering occurs from May to June, pollination is by wind and seed is set from June to September.
Natural dispersal is both by wind and through birds and other animals ingesting the shiny achenes (Ridley 1930). Human transport is probably even more significant, however, Sorrel seed being present in hay, silage or as a contaminant of crop seed (Grime et al. 1988).
Germination and establishment
R. acetosa is characterized by early autumn germination and it exhibits only a transient type of seedbank (ie surviving less than one year). In water meadows or other forms of wet ground, the death of flood-intolerant achenes results in a lack of multiple post-flood germination cohorts. Taken together these seed properties limit R. acetosa in river and lakeshore flood-plains to rarely flooded grasslands, where the plants face a relatively high level of competitive interactions. This contrasts strongly with the flood-tolerant properties of the related wetland species, R. crispus (Curled Dock) (Voesenek & Blom 1992).
British and Irish occurrence
Analysis of the 2002 New Atlas hexad survey results for the whole of B & I indicates that R. acetosa is the most widely recorded Dock in these islands, again leading R. obtusifolius, the next most widespread Dock by 52 hexads (Preston et al. 2002).
European and world occurrence
R. acetosa is widespread throughout most of Europe (although rare further south), and Eurasian forms are widely naturalized across N America so that the species sens. lat. has become circumpolar. R. acetosa has also been accidently introduced by agriculture in widely scattered places around the southern hemisphere including S America, S Africa, S Australia and New Zealand (Hulten & Fries 1986, Maps 660, 661).
Uses
The sour taste (or the "grateful acidity", as Grieve 1931 has it) of R. acetosa sap is produced by the oxalate content of the plant which is mildly toxic. The flavour is much less sharp and pungent in springtime and does not really reach its maximum until the plant is in full flower in June and July. Sorrel has an ancient pedigree as a medicine for cleaning or purging the blood, and thus clearing up spots on skin. In the past, the plant was cultivated for its medicinal and edible qualities, its leaves eaten raw as a salad appetiser or digestive, cooked as a pot herb in ragouts, fricassees and soups, or treated as spinach and eaten, for instance, with stewed lamb or veal (Grieve 1931).
The plant was also used much as we use lemons: as a cure for scurvy and in the making of sauces for food such as fish (Grigson 1987). Leaf infusions were drunk to assist the kidneys and to cool fever. Leaves were also used to heal sores, boils, bruises and burns, presumably being made into poultices. They were also used to staunch bleeding and to treat a range of ailments from jaundice to heart trouble (Grieve 1931; Allen & Hatfield 2004).
Names
The genus name 'Rumex' is an old Latin name for Sorrel from Pliny derived from the Latin 'rumo' to suck, from the Roman habit of sucking Sorrel leaves to allay thirst (Johnson & Smith 1946). The Latin specific epithet 'acetosa' is derived from 'acetum' meaning vinegar, from the acid taste of the plant. 'Acetosa' and 'Acetosella' were both pre-Linnaean names for Sorrel and any other plant with acid-tasting leaves (Gilbert-Carter 1964; Stearn 1992).
The English common name 'Common Sorrel', or just 'Sorrel', is from the 14th century French 'surelle' or 'sorele', a diminutive from the Low German 'suur' meaning 'sour' or 'acid', a reference to the acidity of the leaves. As such it might be translated as either 'acid plant' or 'sour plant', both of which are appropriate (Prior 1879; Grigson 1974).
No less than 37 English common names are listed by Grigson (1987) and 17 of them include the word element 'sour'. Of the remaining names, several refer to the edible nature of the species, such as 'Bread-and-cheese', 'Donkey's Oats' and 'Green Sauce', while others refer to the spring season then the plant is most edible, eg 'Cuckoo's Meat', 'Cuckoo's Sorrel' or 'Cuckoo's Sorrow'.
In his Typescript Flora of County Fermanagh, Meikle noted that R. acetosa was called "Clock sorrel" by a farmer in Meenagleeragh, because the leaves are similar in shape to a certain style of "Wag at the wall" pendulum clock.
Threats
None.