i8o COMMON WEEDS 



according to Hooker, occurs on gravelly and chalky 

 pastures in England, from Chester and Lincoln south- 

 wards. The flat rosette of leaves destroys the patch 

 of grass upon which it lies. As its name implies, it is 

 usually stemless, and bears sessile or shortly stalked 

 heads an inch or more in length. At the same time it 

 has an extensively creeping rootstock, which makes it 

 difficult to eradicate. 



The Creeping Thistle (Cnicus arvensis Hoffm.) is 

 undoubtedly the worst of all Thistles, and is by some 

 held to be the commonest weed pest of agriculture. 

 Not only is it perennial, but to complicate matters it 

 spreads rapidly by means of an extensive creeping 

 root system (Fig. 50) which develops in all directions ; 

 broken pieces of the rootstock easily take root and 

 give rise to new plants. Flowering stems are sent up 

 from buds which are produced at intervals on the 

 creeping roots, which are whitish or earthy-coloured, 

 and of the thickness of a small quill. Vast numbers 

 of plants of this kind of Thistle produce down in the 

 flower-heads, but no perfectly formed seeds. This has 

 led many farmers to believe that the seeds of the 

 Creeping Thistle do not germinate ; such, however, is 

 not the case, as certain plants produce ripe seeds 

 w r hich germinate and grow into new plants quite 

 readily. The Creeping Thistle occurs both in grass 

 and arable land, and is difficult to eradicate in either. 

 All four of these species of Thistle flower between July 

 and September or October. 



Where Thistles occur in grass land they must be 

 attacked with vigour and persistence. Since the Spear 

 and Marsh Thistles are biennials, they may readily be 

 reduced in numbers by regular cutting and spudding 

 to prevent flowering and seeding, and to this end the 

 spud, sickle, scythe, or thistle cutter (Fig. 4), or in 



