As it is commonly applied, the term weed is applied to any plant which
grows where it is not wanted by, or inconvenient to, man. There are,
however, a considerable number of plants which are included here under
the heading Agricultural Weeds and are very closely linked with man's
farming activities; they have little power to compete with other species
and cannot withstand shade, thus they thrive on soils which have been
disturbed by man.
Most agricultural weeds are described as `native' although in fact they
arrived in the British Isles during Neolithic times when man introduced
agriculture - to our ancestors, the distinction between crops and
weeds was not as clear-cut as it is today;
Aegopodium podagraria
(ground elder,
introduced to the British Isles by the
Romans) was
cultivated until quite recently;
Chenopodium album (goosefoot)
and Polygonum lapathifolium
(persicaria) were both eaten by Tollund Man.
DECLINE IN AGRICULTURAL WEEDS
The decline of agricultural weeds in modern times is due to a number of factors.
One of these is a reduction in the variety of crops. Among the modern changes is the far smaller quantities
of Cannabis and flax which
are now grown. Among the agricultural weeds which have disappeared with
these crops are Camelina sativa (gold-of-pleasure - once itself
grown as a crop) and Orobanche ramosa (hemp broomrape).
Some agricultural weeds have been deceminated by weedkillers; it is
ironical that the species lost to this form of weed control have tended to be the beautiful and
harmless - those which cause the farmer most harm having survived!
Other weeds have succumbed to the efficiency of seed-cleaning. The corn-cockle is one of these and, while
certain of being found in the countryside in the 1970's, a decade later it was at the mercy of man's
attempts to deliberately preserve this beautiful flower.
WEEDKILLERS
Some agricultural weeds have been deceminated by weedkillers; it is ironical that the species lost to this
form of weed control have tended to be the beautiful and harmless - those which cause the farmer
most harm having survived!
Among the harmless species which have been exterminated by the application of weedkillers are shepherd's
needle and Venus's looking-glass - despite this, the real offenders, blackgrass and wild oats have remained.
