IMPROVEMENT OF GRASS LAND 175 



to show up well, to prevent seeding. Where the pest 

 is known to occur the first-year plants, which merely 

 consist of the roots and a large rosette of leaves, should 

 be thoroughly spudded and grubbed out, cutting them 

 off well below the crown. 



Knapweed (Centaurea nigra L.), known under a 

 variety of names, as Hardheads, Hardhack, Black-head, 

 is a too common weed of pastures and meadows, and 

 occasionally present on lawns, occurring especially on 

 clays, loams, and calcareous soils, particularly if in poor 

 condition. It is a perennial plant, with a slender, 

 grooved, usually branched and upright stem, with 

 scattered variable hairy leaves, the upper ones narrow 

 and tapering (Fig. 48). The small purple flowers 

 appear in June to September, grouped together in 

 dense globose heads of about i inch in diameter, hard 

 and black or dark brown. The heads are not prickly, 

 but roughish. 



Knapweed is chiefly harmful on account of the fact 

 that it is a useless plant in grass land, with tough, hard 

 stems which are avoided by stock, although the young 

 leaves are readily eaten by cattle and sheep. If allowed 

 to seed it spreads and becomes very troublesome, 

 rendering pastures unsightly, and usurping space which 

 should be occupied by better herbage. 



Where practicable, Hardhead should be combated 

 by early cutting to prevent seeding, and the plants may 

 be hand pulled in damp weather, though as the root 

 system is large and the plant perennial, pieces are 

 often left in the soil to grow again. The best method 

 of dealing with it is to manure the land liberally so as 

 to encourage better vegetation. A good dressing for 

 this purpose is cwt. sulphate of ammonia, 3 to 4 

 cwt. superphosphate, 2 to 3 cwt. kainit per acre, 

 which should be applied every year until the grasses 



