454 COMPOSITAE (COMPOSITE FAMILY) 



stems with sustenance. Alternate with such crops as clover and 

 rye, which may be cut often for soiling or may be plowed under to 

 furnish green manure for another well-tilled hoed crop. 



GREAT OR GIANT RAGWEED 

 Ambrosia trifida, L. 



Other English names: Tall Ambrosia, Kinghead, Crownweed, Wild 

 Hemp, Big BitterTveed, Horseweed, Horse Cane. 



Native. Annual. Propagates by seeds. 



Time of bloom: July to September. 



Seed-time: August to November. 



Range: Nova Scotia to Florida, westward to the Northwest Terri- 

 tory, Nebraska, Colorado, and Arkansas. 



Habitat : Moist, rich soil ; fields and waste 



A huge, coarse plant, occupying so much 

 room and feeding so grossly that crops grow- 

 ing with it are crowded and starved to 

 death. Its usual height is four to ten feet, 

 but on very fertile river bottom-lands it 

 attains to twelve and even fifteen feet. 



Stem stout, tough, woody, widely branched 

 and rough with bristly hairs. Leaves also 

 rough-hairy and varying greatly in shape, 

 often more than a foot long, mostly three- 

 parted, but some may have five lobes and 

 yet others may be ovate or lance-shaped; 

 usually they are coarsely toothed but the 

 smaller upper ones are often entire ; all are 

 opposite, three-nerved, the petioles stout and 

 margined. Sterile heads in racemes six inches 

 to a foot in length, their involucres three- 

 ribbed on the outer side with scalloped 

 margins. Fertile involucres clustered in the 

 axils of the upper leaves. These form a 



fruit a quarter-inch or more long, brown, 

 FIG. 317. Giant , , / -11 , 



Ragweed (Ambrosia tri- obovoid, five- or six-ribbed, with a conic 



fida). x f. beak at apex surrounded by five or six 



