452 



COMPOSITAE (COMPOSITE FAMILY) 



Before flowering, this coarse weed somewhat resembles the 

 Great Ragweed (Ambrosia trifida), for the young plants have nearly 

 the same habits of growth and leaf outlines ; but as soon as they 

 mature the likeness disappears . Stem stout, 

 woody, and shrub-like, much branched, 

 three to eight feet tall. The lower part of 

 the plant is smooth, but the upper leaves 

 and branches are somewhat roughened 

 with minute hairs. Leaves mostly op- 

 posite, broadly ovate, coarsely and very 

 irregularly toothed, roughish above, three- 

 nerved, narrowed abruptly to a stiff peti- 

 ole ; the lowermost ones are sometimes 

 heart-shaped, six inches or more long and 

 nearly as wide. Heads small and green- 

 ish, in large terminal panicles and lesser 

 axillary clusters, sessile and closely crowded 

 on the branchlets; they are scarcely an 

 eighth of an inch broad, the disk-florets 

 perfect but sterile ; surrounding these are 

 usually five fertile pistillate flowers, with 

 very short tubes or none at all. Achenes 

 usually five in each head, about an eighth 

 of an inch long, ovoid, slightly flattened, 

 varying in color from light brown to nearly black, without pappus. 

 They are sometimes found as an impurity in alfalfa seed. (Fig. 

 315.) 



FIG. 315. Highwater 

 Shrub (Iva xanthifolia) . 



Means of control 



The required tillage of cultivated crops serves to keep the w r eed 

 in subjection. In grain fields many of the young seedlings may be 

 dragged out with a weeding harrow in the spring, when the grain 

 is but a few inches tall. The slightly roughened surface of its 

 upper foliage makes this weed susceptible to injury from chemical 

 spray, and, if treated in time with Iron sulfate or Copper sulfate, 

 all seed development may be prevented. Waste-land plants should 

 be cut, piled, and burned before any seed has ripened. 



