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Rumex

The docks and sorrels, genus Rumex, are a genus of about 200 species of annual, biennial, and perennial herbs in the buckwheat family, Polygonaceae. Members of this genus are common perennial herbs with a worldwide native distribution in temperate and subtropical climates.

Some are nuisance weeds (and are sometimes called dockweed or dock weed), but some are grown for their edible leaves. Rumex species are used as food plants by the larvae of a number of Lepidoptera species, and are the only host plants of the butterflies Lycaena dispar and Lycaena rubidus.

Etymology

Rumex is from the Latin, meaning to suck, alluding to the practice since Roman times of sucking the leaves to alleviate thirst. The name dock is from the Old English docce, meaning tall weed, and other European languages for bundle or tuft.

Description

They are erect plants, usually with long taproots. The fleshy to leathery leaves form a basal rosette at the root. The basal leaves may be different from those near the inflorescence. They may or may not have stipules. Minor leaf veins occur. The leaf blade margins are entire or crenate.

The usually inconspicuous flowers are carried above the leaves in clusters. The fertile flowers are mostly hermaphrodites, or they may be functionally male or female. The flowers and seeds grow on long clusters at the top of a stalk emerging from the basal rosette; in many species, the flowers are green, but in some (such as sheep's sorrel, Rumex acetosella) the flowers and their stems may be brick-red. Each seed is a three-sided achene, often with a round tubercle on one or all three sides.

Taxonomy

The genus was first described by Carl Linnaeus in 1753. Within the family Polygonaceae, it is placed in the subfamily Polygonoideae. The genus Emex was separated from Rumex by Francisco Campderá in 1819 on the basis that it was polygamous (i.e. had both bisexual and unisexual flowers on the same plant). However, some species of Rumex subg. Acetosa also have this characteristic, and most other features that are supposed to distinguish Emex are found in species of Rumex. Accordingly, in 2015, Schuster et al. demoted Emex to a subgenus of Rumex.

Within the subfamily Polygonoideae, Rumex is placed in the tribe Rumiceae, along with the two genera Oxyria and Rheum. It is most closely related to Rheum, which includes Rhubarb.

Species

, Plants of the World Online accepted the following species. A large number of hybrids are also recorded.

Uses

Broad-leaved dock (Rumex obtusifolius) used to be called butter dock because its large leaves were used to wrap and conserve butter.

These plants are edible. The leaves of most species contain oxalic acid and tannin, and many have astringent and slightly purgative qualities. Some species with particularly high levels of oxalic acid are called sorrels (including sheep's sorrel Rumex acetosella, common sorrel Rumex acetosa, and French sorrel Rumex scutatus), and some of these are grown as leaf vegetables or garden herbs for their acidic taste.

In the United Kingdom, Rumex obtusifolius is often found growing near stinging nettles, owing to both species favouring a similar environment, and there is a widely held belief that the underside of the dock leaf, squeezed to extract a little juice, can be rubbed on the skin to counteract the itching caused by brushing against a nettle plant. This home remedy is not supported by any science, although it is possible that the act of rubbing may act as a distracting counterstimulation, or that belief in the dock's effect may provide a placebo effect.

Nutrition

Raw dock is 93% water, 3% carbohydrates, 2% protein, and 1% fat (table). In a reference amount of , it supplies 22 calories and rich amounts (more than 20% of the Daily Value, DV) of vitamin C, vitamin A, and magnesium, with moderate content of several dietary minerals (table).

Fossil record

Several fossil fruits of Rumex sp. have been described from middle Miocene strata of the Fasterholt area near Silkeborg in Central Jutland, Denmark. One fossil fruit of a Rumex species has been extracted from a borehole sample of the Middle Miocene fresh water deposits in Nowy Sacz Basin, West Carpathians, Poland. This fossil fruit is similar to the fruits of the extant species Rumex maritimus and Rumex ucranicus which both have fossil records from the Pliocene and Pleistocene of Europe.

References

External links