Knotgrass

(Polygonumaviculare L., Polygonaceae)

Also Called: Knotweed, Centinode.

Description: Annual plant, very variable according to habitat; in waste places its shoots are weak and scrambling; as a weed of cultivated land it is vigorous, erect up to 40cm (16in) high.
Stems branched, bearing many alternate leaves, which are either narrow and pointed or broadly ovate with rounded apex, 0.5-3cm (0.2-1 in) long.
Flowers indistinct, 2-3mm (0.07-Olin) long, funnel-shaped corolla white, greenish or pink.
Flowering: June-September.

Part Used: Dried flowering plant.

Habitat and Cultivation: Very widely distributed throughout the world.
Common in Britain on roadsides and waste places.
Collected when in flower, dried either in the shade or in sunlight.

Constituents and Action Tannin and silicic acid.
Astringent, used as an antidiarroeal (action of tannin); because of its silicic acid content it may exert a strengthening action on lung tissues and in the treatment (still contested) of pulmonary tuberculosis

Usage: As a tisane (pour 0.5 litre (1 pt) of cold water on 3-4 tablespoonfuls of finely chopped plant and raise to the boil) for diarrhoea.
The powdered drug is also used (a teaspoonful in half a tumbler of water, 3 times daily).