7 6 WEEDS OF FARM LAND 



the vitality of seeds is their power of surviving for prolonged 

 periods when buried in the soil. It is beyond question that 

 weed seeds will lie dormant underground for several years, 

 starting into growth whenever favourable conditions occur, 

 though much discrepancy exists in the estimates of the time 

 that the seeds can endure burial without losing their power of 

 growth. A most striking instance of the abundance of living 

 weed seeds in cultivated soil is afforded by the Somme battle- 

 field. A. W. Hill 1 reports that in July, 1917, acres of poppies 

 were in full flower, forming a stretch of flaming scarlet over 

 wide areas. The poppies were occasionally replaced by a few 

 acres of white chamomile (Matricaria chamomilld] and large 

 patches of yellow charlock (Brassica sinapis) also broke the 

 uniformity. The subsoil of the area is chalk, covered with 

 loam, and the constant shelling has churned the ground up 

 and incorporated the soil and subsoil very thoroughly. The 

 charlock was specially conspicuous on the more recently dug 

 graves of soldiers, where the pure chalk had been brought up 

 to the surface. On the sites of wrecked woods, sheets of 

 rose-bay or fireweed (Epilobium angustifoliuni] were conspicu- 

 ous, and round the edges of the ponds formed by shell holes 

 were bands of toad rush (Juncus bufonius var. gracilis), ac- 

 companied by willow weed (Polygonum persecaria], the latter 

 often growing out of the water. In addition to these domin- 

 ating plants, a large variety of other common arable weeds 

 were present in greater or less amount. It was obviously 

 impossible that these hordes of weed seeds could have been 

 carried by any known means of transport, whether by wind, 

 animals, birds, vehicles, or human beings, and the inference is 

 that they were all present in the soil in great numbers and 

 seized the opportunity to germinate provided for them by the 

 unwonted upheaval of the soil. 



On a small scale a similar phenomenon is familiar to almost 

 every farmer. It is a matter of common knowledge that if 

 arable land is turned up rather more deeply than usual, or if 

 old leys are ploughed up, in the following season large quanti- 

 ties of weeds will appear from seeds which must have been 

 buried in the soil awaiting their chance. Belief goes further, and 

 it is often said that large crops of poppies, charlock, or similar 

 weeds spring up even when " old pasture " is ploughed. In- 



1 Hill, A. W. (1917), "The Flora of the Somme Battlefield," Kew Bull. 

 Misc. Information, Nos. 9 and 10, pp. 297-300. 



