86 COMMON WEEDS 



loamy, and calcareous soils. The fruits are a fairly 

 common impurity in red clover samples and in samples 

 of Italian ryegrass. Like other annuals it must be 

 attacked by means of the hoe and by surface cultivation 

 from quite early in spring, as it flowers and seeds from 

 April onwards. Pure farm seeds should be sown. 



COMPOSITE 



Cornflower, Corn Bluebottle (Centaurea Cyanus L.) is 

 an annual or biennial i to 2 feet high, with blue flowers, 

 and is a favourite garden plant, there being several 

 cultivated varieties of different colours. Flowering takes 

 place from June to September, and the seeds are easily 

 scattered by the wind. Although the Cornflower appears 

 occasionally in grass land, it is, as its name implies, 

 chiefly a weed of cornfields, and it is said to be a good 

 index of poor sandy soils. Hoed crops and surface 

 cultivation during the spring months reduce it ; care 

 should be taken that samples of red clover, trifolium, 

 and grass seeds are free from its seeds. 



Creeping Thistle (Cnicus arvensis L.) is typically a 

 weed of arable land, and is, as stated at p. 180, held 

 by some to be the commonest weed pest of agriculture. 



A general account of this Thistle is given with other 

 species at p. 180, and the harm it does in corn crops 

 is there noted. The creeping roots often run deeply 

 into the soil, and are propagated in every direction 

 horizontally, while the flowers produce an abundance 

 of seed which is distributed by the wind to great dis- 

 tances, thus causing neighbouring crops to be infested. 

 Flowering unfortunately takes place between July and 

 September, during the time of harvest, and the dis- 

 tribution of its seeds is ensured during the process of 

 cutting and carting corn. Where this pest is found in 



