Tall Thoroughwort

Tall Thoroughwort, Tall Boneset, Tall JoePye Weed, Tall White-Top

Eupatorium altissimum L.

Asteraceae (Sunflower Family)

▲ ▼ mature, flowering plants

▲ ▼ flowering stems

▲ ▼ closer view of flowers, inflorescences

▲ ▼ flowers and leaves

▲ ▼ stems and leaves

▲ leaf

▲ plant after flowering, with fruit/seed-- white, puffy "parachutes" (pappus)

Eupatorium altissiumum L., Tall Boneset, Tall Thoroughwort, Tall Joe-Pye Weed: (Bayer Code: EUPAT; US Code EUAL3)

U.S. native creeping perennial that can produce short rhizomes and grows 3-6 feet tall; stems are green to purplish, slightly ridged and hairy in the upper portions; stems usually unbranched until flower formation commences
Leaves are opposite, lanceolate, rough-hairy, with smooth or toothed margins and 3 prominent veins; leaves have short or absent petioles; often a pair of smaller leaves are at the base of upper stem leaves
Head inflorescences are in fairly compact, flat-topped clusters at tips of stems; individual heads are about 0.25 inch diameter, with no ray flowers and white to grayish-white disk flowers
Bracts below each head are in multiple rows, green, oval to linear, very hairy, and have a rounded tip
Flowering is from late summer through mid-autumn
Found in pastures, prairies, dry or rocky fields, open woods; tolerant of infertile soils; common in southwest Missouri pastures
May be toxic to livestock if heavily grazed
May appear similar to Late Boneset (Eupatorium serotinum), but late boneset has more triangular leaves with a distinct petiole, and bracts below inflorescence have a more round-pointed tip, not just rounded

Eupatorium:

Eupatorium is a genus of plants that includes weeds called Boneset, Dogfennel, Eupatorium, Joe-Pyeweed, Thoroughwort, (all of the white-flowered species are also called whitetop.
They are a group of perennial, native weeds that usually are not palatable to livestock, and some are poisonous
Besides the weedy species described, there are several ornamental native species/wildflowers that were previously included in this genus group (now placed in the genus, Eutrochium), that are found in moist soils and have large terminal clusters of white, pink or blue flowers; some have whorled leaves--Sweet JoePye Weed, Spotted JoePye Weed, Hollow-Stemmed JoePye Weed