430 Journal of Agriculture, Victoria. [10 July, 1917. 



rabbits get at this grass they eat. it out, so that St'. John's Wort again 

 takes possession as soon as competition from the grass disappears. 



This seems about on a par with planting coniferous trees to suppress 

 this plant. The close planting of pine trees on Crown lands would, in 

 all probability, successfully arrest the spreading of this pest to clean 

 land, providing the pine belt was a wide one. But in regard to privately- 

 cwned land the owner does not want pine trees ; he wants to put his 

 land to other uses, such as grazing. It has already been stated that 

 Kangaroo grass will smother St.. John's Wort, but to enable it to do this 

 it would be necessary to exclude all stock, including rabbits, for a 

 considerable time. After the weed has disappeared and the stock 

 returned, dormant seeds would in all probability reiufest tlie land as 

 soon as tlie stock had eaten down the controlling grass. 



One thing tliat must, forcibly strike any one who has given any 

 thought to weed suppression is the vei-y lax way in which the Tliistle 

 Act is administered by some of the shires in Victoria. In some shires 

 pi-cclaimed weeds can be noticed growing in the yards of public build- 

 ings without restriction of any kind, and along the footpat'hs and 

 main streets in some of our large inland towns stinkwort may be seen 

 growing abundantly. 



In this paper it is only intended 'to deal with a few of our worst 

 weeds, and, as the first essential in dealing with any weed is to prevent 

 it seeding, this applies to all of them. In fact, the three' main prin- 

 ciples cf weed control are {a) to prevent weeds from going to .seed; {h) 

 preventing the introduction of weed seed ; (r) preventing perennial 

 weeds from making top growth. 



Cutting weeds down is frequently practised, but often this work is 

 don© so late that the seed has already been shed or is distributed in the 

 process of cutting, or it is so far advanced in growth that, it is enabled to 

 continue the ripening process after having been cut down, and if the tops 

 are not aftei-wards gathered up and burnt little benefit has been derived 

 from the labour and expense of cutting. 



With perennial weeds such as the Canadian Thistle {Cardwus 

 arvensis), where cultivation is practised as well as cutting, the former 

 agency often tends to increase the troiible by distributing the under- 

 o-round stems or rhizomes about the land being cultivated, unless the 

 rhizomes are carefully raked up and burnt. Cultivation ati frequent in- 

 tervals will, as has already been stated, kill any plant, as this destroys 

 the leaves, which are really the lungs and the stomach of plants : but, 

 unfortunately, this plant is possessed of extraordinary vitality, and its 

 roots, even when cut into very small fragments, can produce shoots. 



Pulling up plants that have running roots rarely injures the root 

 system. The plant pulled up usually breaks off at. the pointi where it is 

 afctaciied to the liorizontal root, leaving the latter undisturbed. 



The horizontal root, system is often below the reach of the plough, 

 and while the farmer is' busily engaged in pulling and cultivating to 

 destroy the plants appearing above ground, the root system is continu- 

 ally sending up new shoots as soon as the cultivation is relaxed, although 

 i:.hey have been weakened according to the frequency of the cultivation. 

 In fact, the only practicable method for destroying roots of this class is 

 to starve and exhaust them by preventing the formation of leaves or 

 stems above the surface of ground, and so prevent the elaboration of 

 sap, and. in addition, make salt applications. 



