460 COMPOSITAE (COMPOSITE FAMILY) 
SPINY CLOTBUR 
Xdnthium spindsum, L. 
Other English names: Spiny cocklebur, Thorny Burweed, Dagger- 
weed, Dagger Cocklebur, Bathurst Bur. 
Introduced. Annual. 
-Propagates by seeds. 
Time of bloom: July to September. 
Seed-time: September to November. 
Range: Ontario to Florida, westward to Jllinois, Missouri, and 
Texas. Also abundant on the Pacific Coast. 
Habitat: Warm, moist soil; invades almost any crop. 
A very pernicious weed which came to us from tropical America. 
It is sometimes cultivated for the odd appearance of its white-veined, 
Fic. 321.— Spiny Glot- 
bur (Xanthium spinosum). 
ban 
white-lined, dark green leaves, yellow 
spines, and green burs. But these last, 
with their hooked spines, are so easily 
transported on clothing and by animals 
that the plant should be considered an 
undesirable resident of any neighborhood, 
particularly as the fruits retain their 
vitality for years, biding the time when 
some stirring of the soil shall furnish 
them the needed warmth and moisture 
for germination. It is a worse weed than 
the other Cockleburs, for it spreads as 
freely in sod lands as elsewhere. (Fig. 
321.) 
Stem one to three feet tall, many- 
branched and hoary with whitish hairs. 
Leaves alternate, two to five inches long, 
lance-shaped, long-pointed, and narrow- 
ing to short petioles, the lower ones lobed 
and the upper ones entire, white-woolly 
underneath and on midribs and veins 
above. Just below each leaf is a slen- 
der, yellow, three-pronged spine about an 
inch long. Flowers of two kinds, the staminate ones in short 
terminal spikes, the heads very small and greenish, like the 
Ragweed. Fertile flowers in the axils below, consisting of a 
