Eupatorium hyssopifolium
Eupatorium leucolepis
hyssop-leaf boneset, hyssop-leaf thoroughwort
justiceweed, white-bract thoroughwort
(from short caudices or rhizomes) single, sparsely branched distally, pubescent throughout.
(from short caudices or stout rhizomes) single, sparsely branched distally, puberulent throughout (more densely distally and among heads).
usually opposite or whorled (distal sometimes alternate, spreading or horizontal); simple, sessile;
blades 3-nerved from bases (laterals sometimes weak), lance-linear, lance-oblong, or linear, 20–60 × 2–15 mm (lengths mostly 6–40 times widths), bases cuneate, margins entire, laciniate-serrate, or serrate, apices acute, faces scabrous (at least abaxial).
usually opposite (distal sometimes alternate, ascending to vertical);
sessile;
blades pinnately nerved, lance-oblong to linear-oblong, 20–60 × 4–10(–15) mm, bases rounded to cuneate (not connate-perfoliate), margins entire or serrate, apices acute, faces villous (abaxial), scabrous (adaxial), gland-dotted.
5;
corollas 3–3.5 mm.
5;
corollas 3–3.5 mm.
8–10 in 2–3 series, elliptic to oblong, 1.5–5 × 1–1.5 mm, apices obtuse to acute (not mucronate), abaxial faces pubescent throughout (more densely distally).
8–10 in 2–3 series, narrowly elliptic, 2.5–8 × 0.8–1.2 mm, acuminate to attenuate, mucronate, abaxial faces puberulent, gland-dotted.
in corymbiform arrays.
in corymbiform arrays.
2–3 mm;
pappi of 20–30 bristles 3.5–4 mm.
2–3 mm;
pappi of 30–40 bristles 4.5–5 mm.
Eupatorium hyssopifolium
Eupatorium leucolepis
Varieties 2 (2 in the flora).
Eupatorium hyssopifolium includes both diploid and polyploid cytotypes and presents a complex situation taxonomically. The diploids are placed here in var. hyssopifolium, which also includes polyploids and is characterized by relatively narrow leaves. Variety laciniatum has broader leaves and molecular data suggest that it arose through hybridization between var. hyssopifolium and E. serotinum; the name E. torreyanum has been applied to plants of similar morphology, but these are hybrid derivatives of E. serotinum and E. mohrii. It has also been suggested that var. hyssopifolium has hybridized with E. album var. album to form E. saltuense, and with diploids of E. linearifolium to form polyploid populations included here under E. linearifolium. Eupatorium hyssopifolium is characterized by a tendency for the leaves to be whorled, in 3s and 4s, and for axillary buds to produce leaves without expansion of shoots; the combination of whorled leaves and suppressed axillary shoots gives the nodes a somewhat tufted or verticillate appearance.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (2 in the flora).
Eupatorium leucolepis is distinct morphologically by its acuminate to attenuate phyllaries, linear and usually plicate leaves, and phyllotaxy that is almost always strictly opposite to the arrays, with well-separated nodes. Eupatorium leucolepis has recently been shown to include two distinct species, an unnamed diploid that is endemic to Carolina Bay habitats and a series of relatively widespread and mostly polyploid, apomictic populations that include the type. It was recognized after preparation of this treatment that E. novae-angliae (E. leucolepis var. novae-angliae) was derived from hybridization between the unnamed diploid and E. perfoliatum, and is here recognized as a distinct species; it is not directly related genetically to E. leucolepis and thus is not appropriately classified as a variety of it.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaves mostly linear, 2–5 mm wide, margins usually entire or obscurely serrulate | var. hyssopifolium |
1. Leaves mostly lance-linear to lanceolate, 5–15 mm wide, margins usually laciniately toothed | var. laciniatum |
1. Leaf blades strongly folded along midribs, curved, 4–10 mm wide | var. leucolepis |
1. Leaf blades weakly folded along midribs, not curved, 10–15 mm wide | var. novaeangliae |
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