''Eupatorium sessilifolium'', commonly called upland boneset or sessile-leaved boneset, is a North American plant species in the family

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 w ...

. It is native to the eastern and central United States, found from

Maine Maine () is a state in the New England and Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and north ...

south to

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...

and

Alabama (We dare defend our rights) , anthem = "Alabama (state song), Alabama" , image_map = Alabama in United States.svg , seat = Montgomery, Alabama, Montgomery , LargestCity = Huntsville, Alabama, Huntsville , LargestCounty = Baldwin County, Al ...

, and west as far as

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the Osage ...

Kansas Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...

, and

Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...

Description

''Eupatorium sessilifolium'' is a perennial herb with stems that are sometimes more than 100 centimeters (40 inches) tall. They are produced from a woody underground caudice or short

rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

. The top of the stems, where the branching begins to the flower heads, have short hairs, while the lower part of the stems have no hairs. The leaves are arranged in opposite pairs and are toothed. The leaf bases are rounded and the leaves are sessile (lacking stalks), but they do not clasp around the stem. The foliage is dotted with glands. ''Eupatorium sessilifolium'' blooms in August and September (July in the southern part of its range), and the small

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

s are branched and composed of widely spaced, tiny white flower heads in

corymbiform Corymb is a botanical term for an inflorescence with the flowers growing in such a fashion that the outermost are borne on longer pedicels than the inner, bringing all flowers up to a common level. A corymb has a flattish top with a superficial re ...

(flat topped) arrays. The heads typically have five or six

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 w ...

s per head, 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 w ...

Habitat and distribution

''Eupatorium sessilifolium'' is found growing in open woods or edges of woods with soils that have good drainage and it is found uncommonly in prairie remnants. Upland boneset is a threatened species in

Michigan Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and the ...

, and legally protected in that state. It is also a threatened species in

, where only a few populations exist in the extreme south eastern part of the state.

Hybrids

As is common in ''

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 ...

'', ''E. sessilifolium'' can form hybrids with other species in the genus. In particular, ''Eupatorium godfreyanum'' is a hybrid of ''E. sessilifolium'' and ''

Eupatorium rotundifolium ''Eupatorium rotundifolium'', commonly called roundleaf thoroughwort, is a North American species of plant in the family Asteraceae. It native to the eastern and central United States, in all the coastal states from Maine to Texas, and inland as ...

'' (although it reproduces by

apomixis In botany, apomixis is asexual reproduction without fertilization. Its etymology is Greek for "away from" + "mixing". This definition notably does not mention meiosis. Thus "normal asexual reproduction" of plants, such as propagation from cuttin ...

and thus can be found outside the range of the two parent species).

References

External links

photo of herbarium specimen at Missouri Botanical Garden, collected in Missouri in 1993
{{Taxonbar, from=Q5409978 sessilifolium Flora of Canada Flora of the Eastern United States Plants described in 1753 Taxa named by Carl Linnaeus