Dipsacus
Dipsacus is a genus of ca. 15 Old World species, mainly distributed in Eurasia and the Mediterranean region (some in Africa and Asia). Several species are cultivated as ornamentals (see Matthews 2000) and Dipsacus sativus was formerly widely cultivated for the dried inflorescence that was used in preparing cloth. Two species are native in Belgium: Dipsacus fullonum L. and D. pilosus L. (both are also cultivated as ornamentals) (Lambinon & al. 2004).
Some authors accommodate Dipsacus pilosus and D. strigosus in a separate genus, Virga Hill (see for instance Štepánek & Holub 1997; as V. pilosa (L.) Hill and V. strigosa (Willd. ex Roem. et Schult.) Holub respectively). This taxonomic viewpoint is not followed by other recent taxonomists.
1. Cauline leaves sessile, connate at base. Heads ovoid to cylindrical. Corolla (pale) pinkish to purplish, sometimes nearly whitish === 2
1. Cauline leaves shortly petiolate, not connate at base. Heads globose to spherical. Corolla whitish or pale yellow === 4
2. Cauline leaves deeply lobed to pinnatifid === Dipsacus laciniatus
2. Cauline leaves crenate-serrate to nearly entire === 3
3. Receptacular scales with a recurved apical spine. Involucral bracts shorter than the head === D. sativus
3. Receptacular scales with a straight apical spine. Involucral bracts as long as to longer than the head (native) === D. fullonum
4. Corolla pale yellow. Anthers pale yellow or greenish (not contrasting in colour with corolla). Flower head ca. 30-40 mm across. Receptacular scales distinctly longer than corolla, long attentuate and glabrous at apex === D. strigosus
4. Corolla white. Anthers dark purplish to blackish (much contrasting in colour with corolla). Flower head ca. 15-25 mm across. Receptacular scales hardly longer than corolla, abruptly narrowed and ciliate towards apex (native) === D. pilosus
Literature
Hansen A. (1976) Dipsacus. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 4. Cambridge University Press, Cambridge: 58-59.
Jäger E.J. & Werner K. (eds.) (2005) Rothmaler Band 4. Exkursionsflora von Deutschland. Gefässpflanzen: Kritischer Band. Springer Verlag, Berlin: 880 p.
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H. (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.
Matthews V.A. (2000) Dipsacus. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 456-457.
Štepánek J. & Holub J. (1997) Virga and Dipsacus. In: Slavík B. (ed.), Kvetena Ceské Republiky, vol. 5. Academia, Praha: 529-532 and 532-535.