Persicaria maculosa

Persicaria maculosa
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Core eudicots
Order:	Caryophyllales
Family:	Polygonaceae
Genus:	Persicaria
Species:	P. maculosa
Binomial name
Persicaria maculosa L.

Persicaria maculosa (syn. Polygonum persicaria) is an annual plant in the knotweed family, Polygonaceae. Common names include lady's thumb, spotted lady's thumb, Jesusplant, and redshank. It is native to Eurasia and present as an introduced and invasive species in North America, where it was first noted in the Great Lakes region in 1843.

The ochrea: stipules fused around the stem

Taxonomy

There are three varieties:

• 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

This species grows up to 1 meter tall and has narrow, lance-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 appear from early summer to late autumn.

It is native to Europe and Asia, 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 and is naturalised throughout the mainland continent, growing 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 ochrea, something which Pennsylvania smartweed lacks.

Cultivation and uses

This plant contains persicarin and tannins. In medicine, Redshank is used against diarrhoea and infections. 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.