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 Bitterweed, Horseweed, Horse €ane. 
Native. Annual. Propagates by seeds. - 
Time of bloom: July to September. 
Seed-iime: 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 
places. 
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, 
obovoid, five- or six-ribbed, with a conic 
Fie. 317.— Giant 
Ragweed (Ambrosia tri- : 
fida). X}. beak at apex surrounded by five or six 
