452 COMPOSITAE (COMPOSITE FAMILY) 
Before flowering, this coarse weed somewhat resembles the 
Great Ragweed (Ambrdsia trifida), for the young plants have nearly 
the same habits of growth and leaf outlines; but as soon as they 
mature thelikeness 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 verv 
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 
Fig. 315.— Highwater very short tubes or none at all. Achenes 
Shrub (Iva zanthifolia). ysually five in each head, about an eighth 
x4. 5 5 " 
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.) 
Means of control 
The required tillage of cultivated crops serves to keep the weed 
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. 
