The 'Redshank' (''Persicaria maculosa'', formerly ''Polygonum persicaria'') is a
perennial plant from the Knotweed family
Polygonaceae. It is also called 'Persicaria', 'Redleg' or 'Spotted Ladysthumb'.
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''.
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
[1], 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
1. http://plants.usda.gov/java/nameSearch?keywordquery=Persicaria+maculosa&mode=sciname&submit.x=0&submit.y=0