''Eupatorium altissimum'', with the common names tall thoroughwort and tall boneset, is a

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition ...

plant in the

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae ...

family with a native range including much of the eastern and central United States and Canada. It is a tall plant found in open woods, prairies, fields, and waste areas, with white flowers that bloom in the late summer and fall.

Description

''Eupatorium altissimum'' is a perennial herb sometimes more than 150 cm (5 feet) tall. Eupatorium altissimum (3292414635)

Leaves and stems are covered with whitish hairs. Leaves are opposite on the stem and either are

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

or have very short petioles. They are narrow, long and wide. Leaves are

lanceolate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regula ...

with 3 prominent veins underneath and teeth appearing only above the middle of the leaves. ''E. altissimum'' produces a large number of small dull white

flower heads A pseudanthium (Greek for "false flower"; ) is an inflorescence that resembles a flower. The word is sometimes used for other structures that are neither a true flower nor a true inflorescence. Examples of pseudanthia include flower heads, compos ...

in a large flat-topped array at the top of the plant. Each head generally has 5

disc floret The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae we ...

s but no

ray florets The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae we ...

. The species is often confused with ''

Brickellia eupatorioides ''Brickellia eupatorioides'', or false boneset, is a North American species of flowering plants in the family Asteraceae. It is widespread in Mexico from Chihuahua to Oaxaca, and in all regions of the contiguous United States except New England, ...

'' (false boneset) because the flowers look similar and because both grow on limestone soils. However, the leaves of ''E. altissium'' are opposite with 3 prominent veins, while the leaves of ''B. eupatoioides'' are alternate with 1 prominent vein. Also, ''E. altissium'' flower heads consist of 5 florets, while the flower heads of ''B. eupatorioides'' have 6 to 15 florets.

Taxonomy

''Eupatorium altissimum'' is part of ''

Eupatorium ''Eupatorium'' is a genus of flowering plants in the family Asteraceae, containing from 36 to 60 species depending on the classification system. Most are herbaceous perennials growing to tall. A few are shrubs. The genus is native to temperate ...

'' even when that genus is defined narrowly to include about 40 species of mostly white-flowered plants of North America,

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an ...

, and

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...

Distribution and habitat

''E. altissimum'' is native to eastern and central North America, from

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central C ...

in the north,

Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the so ...

in the west,

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

and the

Florida Panhandle The Florida Panhandle (also West Florida and Northwest Florida) is the northwestern part of the U.S. state of Florida; it is a salient roughly long and wide, lying between Alabama on the north and the west, Georgia on the north, and the G ...

in the south, and

Massachusetts Massachusetts (Massachusett language, Massachusett: ''Muhsachuweesut assachusett writing systems, məhswatʃəwiːsət'' English: , ), officially the Commonwealth of Massachusetts, is the most populous U.S. state, state in the New England ...

in the east. It almost always grows on

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

soils in prairies, open woods, fields, and neglected areas.

Ecology

The plant blooms from August to October. It attracts various pollinators and is a larval host plant for ''

Schinia trifascia ''Schinia trifascia'', the three-lined flower moth, is a moth of the family Noctuidae. The species was first described by Jacob Hübner Jacob Hübner (20 June 1761 – 13 September 1826, in Augsburg) was a German entomologist. He was the autho ...

'' (three-lined flower moth. It can hybridize with ''

Eupatorium serotinum ''Eupatorium serotinum'', also known as late boneset or late thoroughwort, is a fall-blooming herbaceous plant native to North America. ''Eupatorium serotinum'' ranges throughout most of the eastern United States, found in every coastal state fr ...

''.

References

External links

* *
Photo of herbarium specimen at Missouri Botanical Garden, collected in Missouri in 2014
{{Taxonbar, from=Q5409935 altissimum Flora of North America Plants described in 1753 Taxa named by Carl Linnaeus