68 



FIG. 29. 



CANADA THISTLE, OR CREEPING THISTLE. 

 Carduus arvensis (L. & ROBS). 



This weed was originally introduced from Europe, and hence incor- 

 Tectly named Canada Thistle. It is a hardy perennial, with numerous 

 underground stems which bear a large number of shoots. (See Fig. 29, 

 illustrating two of these shoots.) It grows to a height of 1 to 3 feet. 

 The leaves are narrow and long, deeply indented into very prickly, lobed 

 segments. The leaf has a crimped appearance, and at the base slightly 

 clasps the stem. The under surface of the leaf is woolly, the upper 

 surface less so. It produces numerous heads containing flowers, which 

 are ^ to f inches across and of a lilac-purple color. The flower is smaller 

 than that of other thistles. The seed is grey, oblong, and about J in. 

 long, with slight longtitudinal markings. Attached to the top is a con- 

 spicuous tuft of long hairs (the pappus) (Fig. 29, a). The seed is carried 

 long distances by the wind. An average plant produces 3,500 seeds. 



Time of flowering, June- August. Time of seeding, July-September. 



Dispersal chiefly by the wind. 



Great care should be taken to prevent Canada Thistle from seeding. 



Eradication. The Canada Thistle can be eradicated in several 

 ways, if thorough work is done at the right time : 



1st. By careful and persistent spudding, done in such a way as to 

 prevent the plant from developing top above the ground. 



2nd. By early after-harvest cultivation of stubble ground. 



3rd. By the frequent introduction of hoed crops into the rotation. 



4th. By seeding much with clover, taking one or two crops of hay, 

 plowing the clover sod shallow early after harvest, and cultivating 

 frequently throughout the fall. 



5th. By summer-fallowing. 



Assuming that all land should be plowed in the fall, we may outline 

 -very briefly one or two methods of destroying thistles : 



(1) In stubble ground for spring crop. Gang-plow shallow and 

 harrow early after harvest (immediately after the crop is off) ; and as 

 soon as seeds have had time to sprout or thistles begin to appear, cultivate 

 thoroughly with a broad-share cultivator, the points or shares overlap- 

 ping far enough to cut all plants ; and harrow again, to pull up and 

 expose the plants that have been cut. Repeat the cultivation at inter- 

 vals throughout the fall, and plow in the usual way, or, if possible, rib 

 up with a double mould-board plow just before the frost. This systema- 

 tic cultivation from harvest till winter, will check thistles and other 

 weeds very much, and when followed by a hoed crop (mangels, corn, 

 turnips, carrots, beans, or rape), properly cultivated, it will not only clean 

 the land, but put it into good shape for a crop of grain (oats, barley, etc.,) 

 the next spring, which crop should be seeded with red clover. 



