''Persicaria maculosa'' (syn. ''Polygonum persicaria'') is an

annual plant An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one growing season, and then dies. The length of growing seasons and period in which they take place vary according to geographical ...

in the buckwheat family,

Polygonaceae The Polygonaceae are a family of flowering plants known informally as the knotweed family or smartweed—buckwheat family in the United States. The name is based on the genus ''Polygonum'', and was first used by Antoine Laurent de Jussieu in 1789 ...

. Common names include lady's thumb, spotted lady's thumb, Jesusplant, and redshank. It is widespread across Eurasia from Iceland south to Portugal and east to Japan.Flora of China, ''Polygonum persicaria'' Linnaeus, 1753. 蓼 liao
/ref> It is also present as an introduced and

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

in North America, where it was first noted in the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...

region in 1843 and has now spread through most of the continent.

Ocreae of a Persicaria maculosa 2006-aug-10 Gothenburg Sweden

Description

''Persicaria maculosa'' is an annual herb up to tall, with an erect, rather floppy stem with swollen joints. The leaves are alternate and almost stalkless. The leaf blades often have a brown or black spot in the centre and are narrowly ovate and have entire margins. Each leaf base has stipules which are fused into a stem-enclosing sheath that is loose and fringed with long hairs at the upper end. The

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

is a dense spike. The perianth of each tiny pink flower consists of four or five lobes, fused near the base. There are six stamens, two fused carpels and two styles. The fruit is a shiny black, three-edged

achene An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not ope ...

. This plant flowers from July to September in the temperate Northern Hemisphere.

Taxonomy

The species was first described, as ''Polygonum persicaria'', by

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

in 1753. It was first successfully transferred to the genus ''

Persicaria ''Persicaria'' is a genus of herbaceous flowering plants in the knotweed family, Polygonaceae. Plants of the genus are known commonly as knotweeds or smartweeds.Samuel Frederick Gray Samuel Frederick Gray (10 December 1766 – 12 April 1828) was a British botanist, mycologist, and pharmacologist. He was the father of the zoologists John Edward Gray and George Robert Gray. Background He was the son of Samuel Gray, a London s ...

in 1821, under the name ''Persicaria maculosa''. The name "''Persicaria persicaria''" cannot be used because

tautonym A tautonym is a scientific name of a species in which both parts of the name have the same spelling, such as ''Rattus rattus''. The first part of the name is the name of the genus and the second part is referred to as the ''specific epithet'' in ...

s – binomial names that use the same word for both the genus and the species epithet – are prohibited by the

International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...

, and a replacement name (''

nomen novum In biological nomenclature, a ''nomen novum'' (Latin for "new name"), new replacement name (or replacement name, new substitute name, substitute name) is a scientific name that is created specifically to replace another scientific name, but only w ...

'') must be used. For this reason the transfer of the species to ''Persicaria'' by

John Kunkel Small John Kunkel Small (January 31, 1869 – January 20, 1938) was an American botanist. Born on January 31, 1869, in Harrisburg Pennsylvania, Kunkel studied botany at Franklin & Marshall College and Columbia University. He was the first Curator of ...

in 1903, which used the tautonym, is invalid.

Distribution and habitat

''Persicaria maculosa'' is native to

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

and

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

, where it can be mistaken for '' Polygonum minus''. The latter has narrower leaves, usually less than 1 cm wide. It has been introduced to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

and is naturalised throughout the mainland continent, growing along roadsides, riverbanks, and on fallow ground. In the United States, it is very similar to Pennsylvania smartweed, but redshank has a fringe of hairs at the top of the

ochrea An ochrea (Latin ''ocrea'', greave or protective legging), also spelled ocrea, is a plant structure formed of stipules fused into a sheath surrounding the stem, and is typically found in the Polygonaceae The Polygonaceae are a family of flower ...

, something which Pennsylvania smartweed lacks. The species has also been found in New Zealand and Australia.

Ecology

In the British Isles, this plant is a weed, without natural habitat, and always associated with human activity. It likes moist soils, particularly rich ones, and acid peaty loams. It does not like lime, and liming is cited as a means to fight it.

Cultivation and uses

''Persicaria maculosa'' contains persicarin and

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'', ...

s. The young leaves may be eaten as a

leaf vegetable Leaf vegetables, also called leafy greens, pot herbs, vegetable greens, or simply greens, are plant leaves eaten as a vegetable, sometimes accompanied by tender petioles and shoots. Leaf vegetables eaten raw in a salad can be called salad gre ...

. It is often seen as a weed and rarely cultivated. A yellow dye can be produced from this plant with

alum An alum () is a type of chemical compound, usually a hydrated double salt, double sulfate salt (chemistry), salt of aluminium with the general chemical formula, formula , where is a valence (chemistry), monovalent cation such as potassium or a ...

used as a

mordant A mordant or dye fixative is a substance used to set (i.e. bind) dyes on fabrics by forming a coordination complex with the dye, which then attaches to the fabric (or tissue). It may be used for dyeing fabrics or for intensifying stains in ...

References

External links

photo of herbarium specimen at Missouri Botanical Garden, collected in Missouri in 1983
{{Taxonbar, from=Q161717 maculosa Flora of Europe Flora of Asia Plants described in 1753 Taxa named by Samuel Frederick Gray