THE KINDS OF WEEDS 229 



the spraying should be repeated as often as there is development of 

 new foliage to a marked degree. 



In general, better results are secured from applications made in 

 cloudy weather, although any weather, except that followed by rain, 

 is satisfactory. 



Treatment for Particular Weeds 



Poison ivy and similar woody-rooted pests can be eradicated by cutting 

 off the tops in hot, dry weather in midsummer and pouring a saturated 

 solution of caustic soda about the roots. The arsenical solutions men- 

 tioned above can be used, but are generally objectionable because they 

 render the soil sterile for so long a period thereafter. 



Prickly lettuce (Lactuca Scariola), called also milk-thistle, English 

 thistle, and compass plant. Biennial or annual. Mow the plants 

 repeatedly as they first begin to blossom. Thorough cultivation with 

 a hoed crop is most effective. Mow and burn mature plants. Most 

 frequently introduced as an impurity in clover, millet, and the heavier 

 grass seeds. 



Bracted plantain (Plantago aristata). Annual. Employ hand 

 pulling and burning. If well established, a series of hoed crops may be 

 necessary to eradicate. In permanent pasture, mow the plants as the 

 seed stalks first appear. 



Horse nettle (Solanum Carolinense). Perennial. Keep the plants 

 mown to prevent seed production. To destroy the roots, practice 

 clean cultivation and grubbing or spudding to prevent any develop- 

 ment above ground. A thick growth of grain will weaken the roots. 

 After the grain is cut, the land should be immediately plowed and 

 harrowed repeatedly, and then sown to a winter crop. Then follow 

 with a hoed crop. 



Buffalo bur (Solanum rostratum). Annual ; subdued by preventing 

 seed production by mowing as often as the yellow blossoms appear. 



Spiny amaranth (Amarantus spinosus). An annual, subdued by 

 preventing seed production by thorough cultivation, mowing, or grub- 

 bing out the plant before the flower spikes develop. An intertilled 

 crop followed by a winter crop will keep down the weed. 



Spiny cocklebur (Xanthium spinosum). Annual; maybe choked 

 down by any quick-growing crop that will crowd and shade it. In 

 permanent pastures and waste places mow the plants twice a year, in 



