Weeds are native plants that grow where farmers do not want them. Hence Ehrenfried Pfeiffer (1970) says weeds are weeds ‘only from our human egotistical point of view, because they grow where we do not want them. In Nature, however, they play an important and interesting role. They resist conditions which cultivated plants cannot resist, such as drought, acidity of soil, lack of humus, mineral deficiencies, as well as a one-sidedness of minerals, etc. They are witness of man’s failure to master the soil, and they grow abundantly wherever man has ‘missed the train’ – they only indicate our errors and Nature’s corrections…Weeds are specialists. Having learned something in the battle for survival they will survive under circumstances where our cultivated plants, softened through centuries of protection and breeding, cannot stand up against Nature’s caprices.’
Wine-growers with high aesthetic values seem especially intolerant of them. However, as Ehrenfried Pfeiffer (1970: p.10-11) pointed out, weeds can happily’ resist conditions which cultivated plants cannot resist, such as drought, acidity of soil, lack of humus, mineral deficiencies, as well as a one-sidedness of minerals, etc. They are witness of man’s failure to master the soil, and they grow abundantly wherever man has ‘missed the train’ – they only indicate our errors and Nature’s corrections…Weeds are specialists. Having learned something in the battle for survival they will survive under circumstances where our cultivated plants, softened through centuries of protection and breeding, cannot stand up against Nature’s caprices.’
Controlling weeds: Annual weeds are more easily controlled via herbicides or cultivation than perennial weeds. See also weed manures.
Weeds as indicators: ‘Weeds have a lot to tell us – usually something we don’t want to hear,’ (Jeff Poppen, 2001, p.87). In Lives: Coriolanus (110 AD) Plutarch wrote ‘the richest soil if uncultivated produces the rankest weeds.’ In A Fable for Critics, the poet Robert Lowell suggested that ‘a weed is no more than a flower in disguise.’ In Fortunes of the Republic, Ralph Waldo Emerson asked, ‘What is a weed? A Plant whose virtues have not yet been discovered.’
Groups of weeds: Ehrenfried Pfeiffer (1970, p.12) says there are three major and several minor groups of weeds, the major ones being weeds living on acid soil, weeds living on hard pan, and weeds of cultivation (1970, p.12).
1) Weeds living on acid Soil: Weeds living on acid soil and indicating increasing acidity include the Sorrels, Docks, Fingerleaf Weeds, Briars, broom sedge and Lady’s Thumb, and Horsetail on slightly acid soil. Weeds living on very acid soil, due mainly to either wrong cultivation and/or insufficient drainage include Cinquefoil [see Philbrick & Gregg: 1966, p.21-22], Swampy Horsetail, with Hawkweed and Knapwed on the “wild” soils. Weeds living on slightly acid soil, due to insufficient cultivation include Daisies, Horsetail, Field Sorrel, Prostrate Knotweed. Jeff Poppen (2001, p.87) says that a pasture with daisies, fleabane, goldenrod and not much clover may also be acid and will need liming.
Pfeiffer says the acid loving groups of weeds are our best “guards”, for they indicate exactly when changes in the soil begin. Pfeiffer (1970, p.12-13) says that acidity in soil increases with lack of air, standing water in the surface layer, cultivating of too wet a soil, insufficient cultivation, insufficient drainage, the use of the wrong type of fertilizers (ie acid fertilizers), increasing sheet erosion and, most important of all he says, loss of humus. On pastures felt-like formations of roots and mosses will appear. Even where natural limestone is underneath we frequently find acid-loving weeds, because the top layer of the soil has been de-limed through one-sided cultivation and loss of humus or excessive use of acid fertilizer. This is the case when grain repeats itself too frequently in a crop rotation. Long rest in pasture, alfalfa and clover is then required.’
Weeds which Pfeiffer cites for salty soils include Shepherd’s Purse, Russian Thistle, Sea Plantain, Sea Aster, Artemisia Maritima.
2) Weeds Living on Hard Pan: Pfeiffer cites weeds like Field Mustard, the Horse Nettle, Penny Cress, Morning Glory and Quack Grass, the Chamomiles and Pine Apple Weed as indicating a crust formation and/or hard pan in the soil. Poppen (2001, p.87) says Pennsylvania smartweed indicates a hard pan and poor drainage.
A hard pan is formed, Pfeiffer says, when wet soil is ploughed or when standing water dries up in the surface layers. A hard crust is also formed when mistakes are made, such as too wet discing and rolling, or when a soil dries up after having been cultivated before it has settled and as a consequence of too deep ploughing. Pfeiffer adds that ‘a hard crust also forms when fields are too frequently put into grain crops with insufficient root and manure crops rotating in between. One sided fertilizer application, particularly excess of potassium, will see the arrival of the likes of Wild Mustard and related weeds of the Cruciferae family (but not Shepherd’s Purse and Cochlearea officianalis), and also the Horse Nettle.’
Poppen (2001, p.87) says yellow dock, wild mustard and wild carrots signify a hard pan below where the plough reaches – their tap roots punch holes in a hard pan, allowing room for drainage and air, and space for worms to descend and bring previously unavailable minerals up to the topsoil. Morning glories also signify a hard pan, and crust formation – the result of too much discing of ground when it is too wet. Thorny horse-nettle likes a crusted soil. Plantain was called ‘white man’s footsteps’ by the Native Americans when Europeans introduced it to America – it grows on the compacted soil where people lived (paths, roadways). Relieves stings, cuts and bruises. Nature deals with crusted soils by sending in the grasses to help out: Johnson grass, quack grass, Bermuda grass, goose grass. These improve soil structure with their thatch production.
3) Weeds of Cultivation: The third major group of weeds Pfeiffer identifies consists of those weeds which follow human steps and cultivation, frequently spreading out with compost, manure and wherever man has “walked” on previously farmed soil. These include Lamb’s Quarters, Plantain, Chickweed, Buttercup, Dandelion, Nettle, Prostrate Knotweed, Prickly Lettuce, Field Speedwell, Rough Pigweed, Common Horehound, Celandine, Mallows, Carpetweed, and similar plants.
4) Minor Groups of Weeds: These are the weeds which Pfeiffer (1970, p.12) says ‘show up here and there; they are not necessarily weeds, unless encouraged by man. They are more or less an extension of nature into the realm of man.’ Here he includes ‘many weeds of the Rose family, indicating mainly a lack of care and cultivation. Here are also the pleasant weeds of the Pink and the useful Legume families, the weeds of the latter preferring often light sandy and poor soil, whilst the former thrive on rocky, gravelly soils and along hedgerows on the edges of woods – a real “borderline” group between cultivated and uncultivated nature.’
Bibliography
Ehrenfried Pfeiffer, ‘Weeds and What They Tell’ (Biodynamic Farming & Gardening Association, Inc. USA), 1970, p.10-11.
Jeff Poppen, The Barefoot Farmer (USA, 2001, p.87).