Chapter Sixteen 

 WEEDS 



Weeds are plants of any kind growing where they are 

 undesirable. Lawn grass in a tennis court, morning glories 

 in the lawn, or petunias with the roses are weeds, even 

 though each may be highly desirable in the proper place. 

 Weeds are undesirable for many reasons: they give the place 

 a neglected appearance, they compete with the desirable 

 plants for light, they may actually crowd other plants, as the 

 rosette weeds in the lawn, their root systems compete with 

 other plants for water and mineral nutrients. "Good" weeds 

 must have efficient methods of reproduction, either vegeta- 

 tive or seeds or both, and they must have such remarkable 

 vigor that they frequently grow much faster than the culti- 

 vated plants, which favors them in their competition with 

 the desired plants. 



All plants, including weeds, may be divided according to 

 the length of time they live and produce seeds, into annuals, 

 biennials, or perennials. Annuals, such as crab grass, grow 

 from seed and produce seed the same summer, after which 

 they die. Winter annuals, such as shepherd's purse, grow 

 a rosette of leaves and often a fleshy tap root late in the sum- 

 mer, rest over the winter, and send up a stalk bearing seeds 

 the next spring, after which they die. Biennials start from 

 seed in the spring and grow a rosette of leaves and a fleshy 

 tap root. The next spring the stored food of the root aids 

 in producing the flowering stalk which bears seeds and dies 

 later in the same summer. Figure 18 shows the growth we 

 normally see the first summer, as well as the type of growth 

 made the following season. Most biennials grow a large 

 flowering shoot the second season. 



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