Rudbeckia L.
Rudbeckia is a genus with exclusively North American species. The generic and specific boundaries have long been controversial. Species numbers, even among recent authors, range from 23 (Urbatsch & Cox 2006, Mabberley 2008) to only 13-15 (Wangdin & Knees 2000, Jäger & al. 2008) or even less. As currently understood and in accordance with DNA-based phylogenetic analyses Rudbeckia now includes the monotypic genus Dracopis Cass. (see Urbatsch & Cox 2006).
Most species of Rudbeckia have very showy flower heads. Several are therefore cultivated as ornamentals. Up-to-date accounts for the genus in cultivation in Europe are provided by Wangdin & Knees (2000) and Jäger & al. (2008). Some species might have been overlooked as a result of confusion with the species treated in this account.
1. Glabrous annual. Mid cauline leaves clasping-amplexicaul === 1. Rudbeckia amplexicaulis
1. Hirsute biennial (rarely annual) or glabrous perennial. Mid cauline leaves never clasping-amplexicaul === 2
2. Mid cauline leaves pinnatifid, usually with 5-9 lobes. Robust (often more than 200 cm), glabrous perennial === 4. R. laciniata
2. Mid cauline leaves never pinnatifid, entire or slightly lobed. Smaller (rarely exceeding 100 cm), hairy biennial (rarely annual) or perennial === 3
3. Sparsely hairy to nearly glabrous, stoloniferous perennial. Pappus coroniform, ca. 0,2 mm === 2. R. fulgida
3. Bristly-hairy, taprooted biennial or perennial (rarely annual). Pappus absent === 3. R. hirta
Literature:
Cox P.B. & Urbatsch L.E. (1994) A taxonomic revision of Rudbeckia subg. Macroline (Asteraceae: Heliantheae: Rudbeckiinae). Castanea 59: 300-318.
Dress W.J. (1961) Notes on the cultivated Compositae, 6. The coneflowers: Dracopsis, Echinacea, Ratibida, and Rudbeckia. Baileya 9: 67-93.
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Perdue R.E. (1957) Synopsis of Rudbeckia subgenus Rudbeckia. Rhodora 59: 293-299.
Urbatsch L.E. & Cox P.B. (2006) Rudbeckia. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 21. Oxford University Press, New York-Oxford: 44-60.
Wangdin T. & Knees S.G. (2000) Rudbeckia. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 647-648.