76 



FIG. 33. 



PERENNIAL Sow THISTLE, FIELD Sow THISTLE, OR CORN Sow 



THISTLE. 



Sonchus arvensis (L). 



A perennial weed, 1 to 3 feet high, with large and vigorous root- 

 stocks, full of a milky white juice. The stems are rough, and the growth 

 of the lower part of the plant is rank. The leaves are deeply cut and 

 furnished with small spines, and at their base clasp the stem. The flowers 

 are bright yellow, of fair size, J in. across, and quite similar to those of 

 the Dandelion. They close up in strong sunlight. The calyx, or flower 

 cup, is green and covered with yellowish bristles. The seed is brown' in, 

 color and about J in. long, with both longitudinal and transverse mark- 

 ings. To the top, a tuft of silken hair is attached (Fig. 33, a). An aver- 

 age plant produces about 2,000 seeds. 



Time of flowering, June- August. 



Time of seeding, June-August. 



Dispersal by running rootstocks, and the scattering of seeds by the 

 wind. 



The Sow Thistle draws much water from the soil and is a heavjr 

 feeder. It is less troublesome on stiff clays than elsewhere. 



Note. Fig. 33, nearly natural size, shows the difference between: 

 Annual and Perennial Sow Thistles. 



Eradication. The method used for the eradication of the Canada*; 

 Thistle is recommended for this weed. 



