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''Eupatorium rotundifolium'', commonly called Roundleaf thoroughwort, is a North American species of plant in sunflower family. It native to the eastern and central United States, in all the coastal states from Maine to Texas, and inland as far as Missouri and the Ohio Valley.〔(Biota of North America Program 2014 county distribution map )〕 The stems up to 100 cm (40 inches) tall and are produced from short rhizomes. The inflorescences are composed of a large number of small white flower heads, each with 5 disc florets but no ray florets. Plants can be highly variable due to hybridization, three varieties have been named.〔(Flora of North America, Eupatorium rotundifolium Linnaeus, 1753. Roundleaf thoroughwort )〕 ;Varieties〔 *''Eupatorium rotundifolium'' var. ''ovatum'' (Bigelow) Torr. *''Eupatorium rotundifolium'' var. ''rotundifolium'' *''Eupatorium rotundifolium'' var. ''scabridum'' (Elliott) A.Gray == Hybrids and related species == As is common in ''Eupatorium'', ''E. rotundifolium'' can form hybrids with other species in the genus. In particular, ''Eupatorium godfreyanum'' is a hybrid of ''E. rotundifolium'' and ''Eupatorium sessilifolium''. The plants known as ''Eupatorium rotundifolium'' var. ''saundersii'' have often been treated as a variety of ''E. rotundifolium''. They can be distinguished based on morphology, and molecular evidence also suggests that these plants may be different enough from ''E. rotundifolium'' to recognize them as a species, ''Eupatorium pilosum''.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Eupatorium rotundifolium」の詳細全文を読む スポンサード リンク
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