Many methods have been devised and advocated for the eradication of quackgrass and Canada thistles. The success of any method depends very largely upon soil and weather conditions and a method which has proven entirely successful under one set of conditions has frequently failed when used under somewhat different circumstances.
This means almost sure death to Canada thistles, but often fails with quackgrass and must be adopted advisedly.
Covering with paper: Quackgrass and Canada thistles in patches not over two rods square can sometimes be economically killed by cutting the weeds close to the ground just when in bloom and covering with tar or some other heavy building paper.
Growing alfalfa: Canada thistles have been completely eradicated where good stands of alfalfa were secured and maintained for three years or more.
Canada thistles in many cases spread only by the roots and bear no seeds, while in other instances, where the conditions are favorable, a large amount of seed is produced.
In fact, many farmers even insist that quackgrass and Canada thistles are blessings in disguise because their presence necessitates more intensive preparation of the seed bed, and better and more frequent cultivations of the crop than is often otherwise given.
While there are many perennial weeds which are proving troublesome on Wisconsin farms, two are pre-eminently noxious because of their peculiar nature and habits, viz., quackgrass and Canada thistles. Description of these weeds and the methods whereby they may be destroyed follow.