CEREAL PESTS WEEDS 457 



502. Perennial weeds. Weeds that are able to live 

 from one year to another without reseeding are perennials. 

 They are the worst kind of weeds to eradicate. In addi- 

 tion to seed propagation, perennial weeds are reproduced 

 from, underground parts. These are of two kinds, - 

 running or horizontal roots and underground stems. 

 The Canada thistle, milkweed, and horse nettle have the 

 horizontal roots. Perennial sow thistle, quack grass, and 

 Johnson grass produce underground stems. 



503. Wild garlic (Allium mneale, Linn.) has been called 

 the most injurious weed in the Middle Atlantic states. 

 Garlic bulblets ground with wheat give the flour a very 

 strong, disagreeable flavor, and cause the bread, cake, 

 pastry, and all other products made from it to be unpal- 

 atable. There is the same effect on rye flour. In mill- 

 ing, the garlic bulblets also injure the rolls by forming a 

 varnish-like coating on them. This may so interfere with 

 the grinding as to make it necessary to shut down the 

 mill until the rolls can be cleaned. Stone burs are also 

 seriously affected, and require dressing afterward. On 

 boards of trade, wheat containing much garlic is graded 

 as " rejected," and sells at 20 per cent to 40 per cent lower 

 than No. 2 Red. Garlic in wheat is worst in Maryland, 

 Virginia, and Tennessee. The annual loss to wheat alone 

 due to garlic is estimated to be 1J million dollars. 



Wild garlic propagates almost exclusively by a form of under- 

 ground stem, called a bulb, and by the aerial bulblets above men- 

 tioned. The form most abundant in this country rarely produces 

 seeds. Where the tops of the plants are kept down, wild garlic 

 reproduces by small secondary bulbs or "cloves" formed at the base 

 of the old bulb. These are found in clusters at a depth of 3 to 10 

 inches below the surface of the ground (Fig. 143). After fall rains, 

 they send up tufts of blue-green shoots which become more promi- 

 nent later. These shoots remain green during the winter. In spring 



