CHAPTER VII. 



NOXIOUS WEEDS. 



BY RICHARD HELMS. 



Much depends upon the surroundings and circumstances 

 certain plants are found in to what extent they may become mis- 

 chievous. In cultivated ground all plants which spring up spon- 

 taneously, to the detriment of those specially sown, are noxious, 

 although in other places they may be very useful. For instance, 

 many grasses would soon smother the cultivated plants in a garden, 

 whilst in pasture their usefulness goes unchallenged. Again, other 

 plants, objectionable to the agriculturist or pastoralist, may be much 

 admired by the horticulturist. Considerable elasticity must there- 

 fore be conceded to the term " noxious weeds," as according to 

 different rural pursuits the evil done by certain " weeds " varies. 

 The space occupied by one species of plant, it is certain, cannot at 

 the same time be utilised by another. On this axiom is focussed 

 the objectionable nature of undesirable weeds. The husbandman, 

 whatever his special calling may be, should never neglect bearing 

 this in mind, and constantly endeavour to root up undesirable plants 

 in order that those more useful to him may prosper the better. 



Introduced weeds, as a rule, become so much more harmful in 

 comparison with indigenous plants, chiefly owing to the frequency 

 and rapidity with which they multiply, and great surprise is often 

 expressed at this objectionable proclivity. It is, however, common 

 to many exotics, including animals as well as plants. Throughout 

 nature the struggle for existence is narrowed down to " eat, and be 

 eaten " ; this means that in their original habitat every plant and 

 every animal has a natural enemy, and it is mainly by this means 

 that a check is established to prevent the preponderance of a species 

 and the balance restored. In a new habitat and at a distance from 

 its original home the equalizing agent or natural enemy generally is 

 wanting, and no substitute is found in the native fauna or flora to 

 take its place. A still more important factor influencing the spread 

 of exotic introductions, is the change of climate. The advantages 

 of a mild climate to plants originally found in colder climates is 

 enormous. They develop more luxuriantly ; may, under certain 

 conditions, produce several crops of seeds in succession during the 

 same year ; and may also change their habits considerably. Several 

 instances of plants introduced into Australia from colder climates and 

 distant lands might be quoted as examples. These plants which in 

 their native countries are strictly annuals, dying off at the approach 

 of winter, have become biennials, and in some instances perennials. 



