lady's thumb

Redshank
Scientific classification
Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Caryophyllales
Family:	Polygonaceae
Genus:	Persicaria
Species:	P. maculosa
Binomial name
Persicaria maculosa L.

The Redshank (Persicaria maculosa, formerly Polygonum persicaria) is a perennial plant from the Knotweed family Polygonaceae. It is also called Persicaria, Redleg, Lady's-thumb^[1], Spotted Ladysthumb, and Adam's Plaster in Newfoundland. Native to Europe, it is an invasive species in the Great Lakes region where it was first spotted in 1843.^[2]

Species

There are three varietes known:

• Polygonum persicaria var. angustifolium Beckh.
• Polygonum persicaria var. persicaria
• Polygonum persicaria var. ruderale (Salisb.) Meisn.

Synonyms include P. maculata, P. persicaria, P. ruderalis, P. ruderalis, P. vulgaris, P. dubium, P. fusiforme, P. minus and P. puritanorum.

Growth

It grows up to 1 m high, and has narrow, lancet-shaped leaves 8-10 cm long. The leaves often have a brown or black spot. The white, pink or red flowers are in dense panicles and flower from early summer to late autumn.

It is native to Europe and Asia, where it can be mistaken for Polygonum minus, but P. minus has narrower leaves, usually less than 1 cm wide, while its ear is slimmer.

It has been introduced to North America and is naturalised in all mainland states^[3], being found along roadsides, riverbanks, and on fallow ground. In the USA, it is very similar to Pennsylvania smartweed, but Redshank has a fringe of hairs at the top of the ocrea, something which Pennsylvania smartweed lacks.

Cultivation and uses

This plant contains persicarin and tannins. In medicine, Redshank is used against diarrhoea and infections. Fresh leaves have been used to staunch bleeding.

The leaves and young shoots may be eaten as a palatable and nutritious leaf vegetable. It is often seen as a weed and rarely cultivated.

A yellow dye can be produced from this plant with alum used as a mordant.

Overview

Flower

The Redshank has a ocreae, a thin sheath around the stems.

References

Wikiversity has bloom time data for Persicaria maculosa on the Bloom Clock

Wikispecies has information related to: Persicaria maculosa

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