378 Journal of Agriculture, Victoria. [10 June, 1919, 



EXPERIMENTS IN THE CONTROL OF ST. JOHN'S 



WORT. 



Bij II. W. Davey, F.E.S. 



During the last twelve months, in which I have been more or less en- 

 gaged in conducting experiments for the control of St. John's wort, I have 

 had many opportunities to observe some interesting facts relating to this 

 plant. The one thing that stands out above all others is that rabbit 

 suppression and the control of St. John's wort are inseparable, especially 

 in the Alpine areas. 



St. John's wort is not the smothering plant it is usually supposed, 

 but is largely assisted by the rabbit in suppressing other herbage. Even 

 in the worst weed-infested country, grass or its seeds always appear to 

 be present, although usually in a weakly or dormant condition. This 

 can be proved by an inspection of the country at Bright, recently swept by 

 bush fires, where grasses are now* springing up, and if it were not for 

 the presence of the rabbit, would ultimately crowd out the introduced 

 St. John's wort. These grasses are much quicker growers during the 

 autumn than the pest weed, and would soon establish themselves and 

 compete with it for space if the rabbits did not eat them down and often 

 entirely destroy them. 



Some most interesting examples of weed control by grasses are to 

 be seen at Bright. The wort thrives best under occasional cultivations 

 (providing, of course, that these are not frequent enough to prevent leaf 

 formation), for after the soil has been disturbed, weakly plants quickly 

 show great vigour. The land on which St. John's wort was first intro- 

 duced on the Harrietville-road was always noted for the luxuriant crop 

 of weed it carried. Some years since, a portion of this land was fenced 

 and made rabbit proof, and part of it has been planted with walnut 

 trees. The planted area is still heavily infested, a re«ult of the cultiva- 

 tion ; but on the higher land, which is unplanted, kangaroo grass has 

 made wonderful progress at the expense of the weed, which is fast dis- 

 appearing. 



The old Bright Eace-course has long been heavily infested, and many 

 people still call St. John's wort the " race-course weed." This land 

 affords another example of grass controlling the plant. It was dredged 

 for gold, and later, when taken over by the Forests. Department, was 

 made rabbit-proof and planted with Pinus insignis. The plantation now 

 carries some fine patches of grass, and here and there the wort has 

 been already crowded out. 



The pine plantation at Morgan's Creek affords yet another example. 

 Splendid grass occurs here also, and in many places the weed has quite 

 disappeared, or is so small and weak that it has to be carefully looked 

 • for. 



In the examples mentioned, nothing has been done to assist the grass 

 except to keep the rabbits away, and if they were absent from adjacent 

 Crown lands I feel confident that grass could control the weed. This 

 would be especially so if some seed were sown at intervals, as then 

 quicker results would bo obtained than, as at present, by waiting for 

 the natural grass to recover after the years of ill-treatment it has 

 received from the rabbit. 



* Tliese noU's were written 23id April, 1919. 



