LATE EUPATORIUM, Eupatoriurn
serotinum Michx. 1, lower portion of plant with roots; 2,
upper portion of plant in blossom; 3, flower head; 4, seed.
Perennial, reproducing by seed. Roots shallow, fibrous. Stems
hairy, erect, 3 to 6 feet (0.9 to 1.8 m) tall, upper portion much branched.
Leaves narrow, tapering to a point, petioled, edges toothed; upper
leaves alternate, lower ones opposite. Flower heads small,
cylindrical, of whitish disk flowers only, borne in a compact, flat-topped
cluster at top of plant. Seed narrow, oblong to oval with several
longitudinal ribs and with a tuft of whitish bristles at top. Found
on moist soils in feedlots, old pastures, and wasteland. A number of other
somewhat similar species of Eupatorium (e.g., E. perfoliatum, E.
purpureum, E. altissimum, E. maculatum) are found in
the region, under the common names of thoroughwort, boneset, or joe-pye
weed. They are all more or less similar to this illustration. In several
states, one or more of these are much more common than E. serotinum.