in F. Cuvier, Dict. Sci. Nat. ed.2, 37: 471. 1825
North America, Mexico, introduced in Europe, Asia.
Species 5 (5 in the flora).
Euthamia was formerly included in Solidago. Arrangements of heads, gland-dotted leaves, and DNA sequence data demonstrate that Euthamia should be treated as distinct from Solidago (L. C. Anderson and J. B. Creech 1975; R. D. Noyes and L. H. Rieseberg 1999).
Ambiguous and contradictory information has led to much debate about who named Euthamia (D. J. Sieren 1981; K. N. Gandhi 1999; G. L. Nesom 1999; J. L. Strother 2000). I consider correct authorship for this genus to be as given in Index Nominum Genericorum (http://ravenel.si.edu/botany/ing).
Euthamia is capable of tremendous phenotypic variation. Transitional aspects of a given plant are much more likely to be related to environmental factors than to introgression. Heights of arrays are determined by measuring from the summit of the plant to the bases of proximalmost head-bearing branches.
|1||Stems glabrous and glaucous; arrays of heads not flat-topped, lengths of proximal branches 0.18–0.56 times array heights (creating multistoried aspects to arrays); apices of inner phyllaries acute to acuminate||Euthamia occidentalis|
|1||Stems glabrous or hairy, not glaucous; arrays of heads usually flat-topped or rounded, lengths of proximal branches 0.5–1 times array heights; apices of inner phyllaries obtuse to acute||> 2|
|2||Disc corollas 2.5–3.3(–3.4) mm; involucres 3–4.7(–5.3) mm||> 3|
|2||Disc corollas 3.3–4.8 mm; involucres (4–)4.5–6.3 mm||> 4|
|3||Stems glabrous or glabrate; leaf blades usually 1–3 mm wide (to 6 mm wide in some Maine and Nova Scotia populations), faces glabrous or glabrate, abundantly and prominently gland-dotted||Euthamia caroliniana|
|3||Stems glabrous or densely spreading-hirtellous; leaf blades usually 3–12 mm wide, faces glabrous or densely spreading-hirtellous, usually sparsely and obscurely gland-dotted||Euthamia graminifolia|
|4||Leaf blades linear to lanceolate, lengths 12–49 times widths, gradually reduced distally, faces abundantly and prominently gland-dotted, not pustulate; arrays (25–)35–60% of plant heights||Euthamia gymnospermoides|
|4||Leaf blades lanceolate to narrowly lanceolate, lengths 8–18 times widths, abruptly reduced distally, faces little and obscurely gland-dotted, sometimes pustulate;arrays 6–35% of plant heights||Euthamia leptocephala|
|Author||Arthur Haines +|
|Basionym||Solidago Euthamia +|
|Etymology||Greek eu- , good, well, and thama, crowded, evidently alluding to branching pattern +|
|Illustrator||Yevonn Wilson-Ramsey +|
|Taxon name||Euthamia +|
|Taxon parent||Asteraceae tribe Astereae +|
|Taxon rank||genus +|
|Volume||Volume 20 +|