Eupatorium altissimum L.
Distinguishing Features: leaves elliptic, strongly 3-nerved from the base, pubescent on the underside
Habitat: basic, calcareous soils
Geographic Distribution : widespread, but the sexual diploid phase of the species is restricted to the Ozark region (Arkansas, Missouri) and plants from other parts of the range are polyploid and apomictic.
Similar Species: Eupatorium hyssopifolium usually has whorled leaves, and the two major lateral leaf veins are not conspicuous.
Molecular Data : samples of E. altissimum (DNA #s 711, 1169) differ in ITS sequence from all other species by a minimum of 2 indels and 12 bp changes vs. E. serotinum.
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