COMPOSITAE COMPOSITE FAMILY 
TALL THOROUGHWORT 
Eupatorium altissimum L. 
The Tall Thoroughwort is also sometimes mistaken for White 
Snakeroot, page 341. It is less common than some of the other 
species and grows in dry open places from Pennsylvania and 
Minnesota, south to 
North Carolina and Texas. 
This Thoroughwort re- 
sembles the late-blooming 
species on page 338, in 
that the stems of both are 
densely covered with fine 
hairs, and the blooming 
season, September to frost, 
is the same for both. The 
Tall Thoroughwort grows 
4-8 feet high and is much 
branched near the top. 
Leaves, however, as well 
as the height of the plant, 
should serve to distinguish 
it from White Snakeroot; 
they are strongly 3-ribbed, 
lanceolate, gradually ta- 
pering below into a short petiole, rather thick and rough, toothed 
only above the middle or possibly entire. The lower leaves are 
opposite but the uppermost are alternate. 
The heads are crowded in the large inflorescence but each head 
has only about 5 white flowers. The involucre is bell shaped and 
its bracts are oblong, rounded or blunt and densely hairy. They 
are arranged in about 3 series with the outer shortest. The akenes 
are $-angled and the pappus is composed of slightly roughened, 
slender bristles. 
The Upland Boneset, Eupatorium sessilifolium L., has a tall, 
smooth, branching stem which bears many ovate-lanceolate, serrate 
leaves that are rounded at the base and always opposite and sessile. 
The heads and inflorescence are much like those of Tall Thorough- 
wort, the former about three-quarters of an inch high, and the bracts 
linear-oblong. The plant is found in dry woods from Massachusetts 
and Pennsylvania to Albama and Illinois. It blooms a few weeks 
earlier than the Tall Thoroughwort and lasts as long. 
339 
