KnotgrassBotanical Name: Polyganum aviculare (LINN.)
Family: N.O. Polygonaceae
Synonyms: Knotgrass. Centinode. Ninety-knot. Nine-joints. Allseed. Bird's Tongue. Sparrow Tongue. Red Robin. Armstrong. Cowgrass. Hogweed. Pigweed. Pigrush. Swynel Grass. Swine's Grass.
Part Used: Whole herb.
Habitat: The entire globe.
The Knotgrass is abundant everywhere, a common weed in arable land, on waste ground and by the roadside.
Description: The root is annual, branched and somewhat woody, taking strong hold of the earth; the stems, 1/2 to 6 feet in length, much branched, seldom erect, usually of straggling habit, often quite prostrate and widely spreading. The leaves, alternate and often stalkless, are variable, narrow, lanceshaped or oval, 1/2 to 1 1/2 inch long, issuing from the sheaths of the stipules or ochreae, which are membraneous, white, shining, torn, red at the base and two-lobed. The flowers are minute, in clusters of two to three, in the axils of the stem, barely 1/8 in. long, usually pinkish, sometimes red, green, or dull whitish. In contrast to the other Polygonums, there is little or no honey or scent, so that the flowers are very rarely visited by insects and pollinate themselves by the incurving of the three inner stamens on to the styles. The remaining five stamens alternate with the perianth segments and bend outwards, thus ensuring cross-pollination in addition, should any insect visit the flower.
The plant varies greatly in size. When it grows singly in a favourable soil and clear of other vegetation, it will often cover a circle of a yard or more in diameter, the stems being almost prostrate on the ground and leaves broad and large; but when growing crowded by other plants the stalks become more upright and all the parts are generally smaller.
The stems are smooth, with swollen joints, hence the common names, Nine-joints, Ninety-knots, etc., and when gathered it generally snaps at one of the joints.
It begins flowering in May and continues till September or October. Cleistogamic flowers (which do not open at all and in which therefore self-pollination is necessarily effected) are found under the ochrea, and this species is said also to possess subterranean cleistogamic flowers.
The specific name, aviculare, is from the Latin aviculus, a diminutive of avis (a bird), great numbers of our smaller birds feeding on its seeds. The seeds are useful for every purpose in which those of the allied Buckwheat are employed and are produced in great numbers, hence its local name - Allseed. Some of the older herbals call it Bird's Tongue or Sparrow Tongue, these names arising from the shape of its little, pointed leaves. Its minute reddish flowers gained it the name of Red Robin. From the difficulty of pulling it up, it was called Armstrong, and from the fact that cattle and swine eat it readily, we find it called Cowgrass and Hogweed, Pigweed or Pigrush. Gerard tells us: 'It is given to swine with good successe when they are sicke and will not eat their meate, whereupon the country people so call it Swine's Grass and Swine's Skir. In the Grete Herball (1516) it is called Swynel Grass. Shakespeare (Midsummer Night's Dream) speaks of this plant as 'the hindering Knotgrass,' referring to the belief that its decoction was efficacious in retarding the growth of children and the young of domestic animals.
The larvae of Geometer moths will eat the plant as a substitute for their usual food.
Medicinal Action and Uses: The plant has astringent properties, rendering an infusion of it useful in diarrhoea, bleeding piles and all haemorrhages; it was formerly employed considerably as a vulnerary and styptic.
It has also diuretic properties, for which it has found employment in strangury and as an expellant of stone, the dose recommended in old herbals being 1 drachm of the herb, powdered in wine, taken twice a day.
The decoction was also administered to kill worms.
The fresh juice has been found effectual to stay bleeding of the nose, squirted up the nose and applied to the temples, and made into an ointment it has proved an excellent remedy for sores. Salmon stated: 'Knotgrass is peculiar against spilling of blood, strangury and other kidney affections, cools inflammations, heals wounds and cleanses and heals old filthy ulcers. The Essence for tertians and quartan. The decoction for colick; the Balsam strengthens weak joints, comforts the nerves and tendons, and is prevalent against the gout, being duly and rightly applied morning and evening.' The fruit is emetic and purgative.
The Russian Knotgrass (Polygonum erectum, Linn.) possesses similar astringent properties, and an infusion of this herb is used in diarrhoea and children's summer complaints.
The Alpine Knotweed (P. viviparum, Linn.), a small perennial, only 4 to 8 inches high, found in British mountain alpine pastures, is peculiar in that its slender, spike-like raceme of white or pinkish flowers bears in its lower portion, in place of flowers, little red bulbs (as in certain species of Lilium and Alium), on which the plant depends for its propagation, its fruit rarely maturing.
This species is found in North America, being there the one nearest related to the Bistort, whose properties it shares.