Weeds

Weeds, the name given to all those plants which grow wild in cultivated grounds, and injure the crops; which they do both by choking them and by exhausting the soil. Those weeds which are annuals or biennials, as charlock, yellow rattle, and meilott, may gradually be got rid of by merely cultivating, for a succession of years, such plants as are to be cut before the seeds of the weeds are fully ripe. Perennial weeds, such as couch-grass, can only be removed from the ground by repeated and careful tilling; and for this purpose crops which require much hoeing are advantageously planted, and recourse is had to summer fallowing (see FALLOW) in fields, and frequent weeding in gardens. Thistles and other large weeds are frequently pulled in cornfields before the corn comes into ear, and to prevent their seeding they are cut in pastures. Sedges and rushes, which spring up in great abundance in damp grounds, disappear on thorough draining. Leafy crops which thickly cover the soil prevent the growth of many weeds by the exclusion of air and light. Weeds which have been rooted up form excellent compost for manure. Those which make their appearance in fallow grounds serve for green manuring when they are ploughed down. Cultivated grasses growing in arable fields are weeds there. The seeds of weeds are carried normally by the wind, but may be conveyed by running streams. Weeds are often sown along with crops, the seed being imperfectly cleaned; and they are often spread by manure, conveyed by the droppings of birds, or in the mud clinging to the feet of men and animals. Weeds spread far and near from ill-cleaned hedges. Weeds transferred to new countries sometimes grow more luxuriantly than at home; thus the Anacharis (q.v.) from America almost chokes up ditches and canals in England, and the thistle from Britain is a ruinous pest in some parts of Australia.