66 WEEDS OF FARM LAND 



practically the only effective remedy. Small patches may be 

 cleared by covering them with strong sheets of tarred paper, 

 which in the course of time by excluding the light destroys 

 all vegetation underneath. Such patches must be re-seeded 

 when eradication is complete. 1 The same method may be 

 used for small patches of nettles. 



Such weeds as rushes, willow-weed (Polygonum persecaria) 

 and marsh horsetail (Equisetum palustre} only flourish where 

 there is a plentiful supply of water held up by the soil, so that 

 the land is waterlogged. Such conditions are harmful to most 

 of the plants that are useful in herbage, and in order to im- 

 prove the grass, as well as to eradicate the weeds, draining is 

 the only effective remedy. Marsh thistle (Cirsium palustre} 

 flourishes in damp fields and is also found on hilly pastures 

 at any spot where a spring occurs, but it rarely causes much 

 trouble. 



In nearly every case, if careful attention be given to the 

 matter, it is possible in the course of a few years to clear 

 grass-land of weeds by the above methods without resorting to 

 more drastic measures. Woodwax (Genista tinctorid), how- 

 ever, resists every attempt to eradicate it, and when once 

 established in a favourable position it spreads rapidly and 

 causes great depreciation in the value, of the pasture. Stock 

 refuse to touch it, either green or in hay, and apparently the 

 only way woodwax can be eradicated is to plough up the 

 whole field and keep it under arable cultivation until such 

 time as the land is cleared of the underground parts of the 

 pest. 



On rich pasture land buttercups grow most abundantly and 

 do not yield to ordinary methods of eradication. It has been 

 found that a clearance can be made by ploughing up and care- 

 fully cleaning the land, and then taking at least one root crop 

 off it, which enables still more cleaning to be done. If the 

 land is then seeded with grasses and clover of good quality and 

 is treated generously a good pasture soon results, which may 

 easily provide feed within one year from sowing. 2 



(b) Eradication by Spraying and Manuring Chemical 

 Means. On grass-land, as on arable fields, " chemical means " 

 resolve themselves into treatment by liquid sprays and the 

 application of artificial manures. Here again, however, the 



1 " Cnicus acaulis," Jour. Bd. Agric. (1911), XVII, pp. 907-909. 

 2 Carruthers, W. (1906), "Buttercups in Pastures," your, Roy. Ag. Soc.. 

 LXVII, p. 258. 



