Eupatorium altissimum

Tall thoroughwort
File:Eupatorium altissimum alt.jpg
File:Eupatorium altissimum flower.jpg
Conservation status
Secure (NatureServe)
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Asterales
Family:	Asteraceae
Genus:	Eupatorium
Species:	E. altissimum
Binomial name
Eupatorium altissimum L. 1753 not (L.) L. 1774
Synonyms
Synonymy Eupatorium elatum Salisb. 1796, not validly published, not Steetz 1854 Eupatorium floridanum Raf. ex Torr. & A.Gray, not validly published Eupatorium ramosum Mill. Eupatorium rupestre Raf. Eupatorium saltuense Fernald Uncasia altissima (L.) Greene

Eupatorium altissimum (tall thoroughwort) is a perennial plant whose native range includes much of the eastern and central United States and Canada (Ontario south to Nebraska, eastern Texas, the Florida Panhandle, and Massachusetts. It almost always grows on limestone soils, as does Brickellia eupatorioides, with which it is often confused. It can hybridize with Eupatorium serotinum.

Eupatorium altissimum is a perennial herb sometimes more than 150 cm (5 feet) tall. Leaves and stems are covered with whitish hairs. The plant produces a large number of small white flower heads in a large flat-topped array at the top of the plant. Each head generally has 5 disc florets but no ray florets.

Eupatorium altissimum is part of Eupatorium even when that genus is defined narrowly to include about 40 species of mostly white-flowered plants of North America, Asia, and Europe.

External links

• Missouri Plants, Eupatorium altissimum
• United States Department of Agriculture plants profile
• photo of herbarium specimen at Missouri Botanical Garden, collected in Missouri in 2014