IO8 WEEDS OF THE FARM AND GARDEN 



Howitt suggests that sheep be turned in after 

 harvest; these animals, by close cropping, weaken the 

 underground rootstocks. He suggests, further, that the 

 field be cultivated until about the middle of June ; to keep 

 the tops down and weaken the roots, slightly ridge up 

 the land with a double moldboard plow, then sow rape 

 at the rate of one and one-half pounds per acre ; cultivate 

 the rape every week until it occupies all of the ground. 

 He considers the rape a most excellent weed extermina- 

 tor, which might be applied to many perennial weeds. 



Canada Thistle. The Canada thistle can be treated 

 with the sodium arsenite. No other chemicals, so far as 

 our experiments extend, will entirely destroy this weed. 

 Carbolic acid only partially destroys the roots and the 

 plants shoot up again from below the point of injury, but 

 by repeating the process the Canada thistle can ultimate- 

 ly be exterminated. A good method to eradicate the 

 weed is to plow shallow and cultivate frequently during 

 the summer. The roots of the Canada thistle extend 

 deeply down into the soil, hence for this reason deep cul- 

 tivation will be of no avail. After plowing, the soil 

 should be dragged and the roots exposed to the sun and 

 removed, when possible. It may be necessary to run 

 over the field with a hoe to cut off the stray plants which 

 appear. This method was tried on a patch several years 

 ago and no Canada thistles have since made their appear- 

 ance in this place. Various crops, such as clover and 

 sorghum, are said to be effective in subduing the thistles. 



Of the various chemicals which have been used to ex- 

 terminate Canada thistles none is more effective than 

 sodium arsenite. It is applied at the rate of one and one- 

 half pounds to 52 gallons of water. 



Carbolic acid at the rate of one part to one part water 

 destroys the root where it comes in contact with the mix- 

 ture, and for a little distance beyond. This is not an 

 effective method, as the roots sprout out from below. 



