Cichorium calvum Schultz- Bip. ex Aschers. (NE-Afr., SW-As.) – A very rare and ephemeral alien but probably widely overlooked as a result of confusion with Cichorium intybus or C. endivia. Recorded as a birdseed alien in 2012 in Langemark-Poelkapelle (near a mill, along with Trifolium alexandrinum) and in Rumbeke-Roeselare (dump).
Cichorium calvum seems to be a fairly frequent introduction in Egyptian clover seed (especially in mixtures of Trifolium alexandrinum and T. resupinatum) but it is only recognized in a few European countries. All records are from Germany (Merxmüller 1957, Schnedler 1977, etc.) and Austria (Traxler 1979, Melzer & Barta 1995, etc.). It much resembles Cichorium intybus but has shorter achenes without a pappus and the heads are subtended by a larger, leaf-like bract. According to Kiers (2000) it no longer occurs as a contaminant in Trifolium seed since Cichorium calvum seeds are removed from the packages before selling. However, these recent records from Belgium demonstrate that it is still introduced with birdseed to Europe. It also is in disagreement with recent records from Germany (see for instance Dickoré & al. 2009).
Some authors reject the species rank of Cichorium calvum. Boulos (2002), for instance, reduced it to subspecies rank under Cichorium endivia. However, phylogenetic studies by Kiers (2000) demonstrated that it is reminiscent of Cichorium endivia (and C. pumilum) but clearly distinct.
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Selected literature:
Boulos L. (2002) Flora of Egypt. Vol. 3. (Verbenaceae - Compositae). Al Hadara Publishing: 373 p.
Dickoré W.B., Lewejohann K. & Urner R. (2009): Neufunde, Bestätigungen und Verluste in der Flora von Göttingen (Süd-Niedersachsen). Florist. Rundbr. 42: 5-59.
Kiers A.M. (2000) Endive, chicory and their wild relatives. A systematic and phylogenetic study of Cichorium (Asteraceae). Gorteria Supplement 5: 77 p.
Melzer H. & Barta T. (1995) Orobanche bartlingii Grisebach, die Bartling-Sommerwurz, - neu für das Burgenland und andere Neuigkeiten zur Flora dieses Bundeslandes, sowie von Nieder- und Oberösterreich. Linzer Biologische Beiträge 27(2): 1021-1043.
Merxmüller H. (1957) Compositen-Studien VI: Cichorium calcum Schultz Bip. ex Asch, in. Schweinfurt. Mitt. Bot. Staatssamml. München 17-18: 317-318.
Schnedler W. (1977a) Pflanzen, von denen in der Mitteleuropäischen Literatur selten oder gar keine Abbildungen zu finden sind: Cichorium endivia L. in Trifolium alexandrinum-Äckern. Gött. Flor. Rundbr. 11(4): 96-97.
Schnedler W. (1977b) Pflanzen, von denen in der Mitteleuropäischen Literatur selten oder gar keine Abbildungen zu finden sind. Folge VIII. Berichtigungen zu Cichorium endivia L. Gött. Flor. Rundbr. 11: 97-102.
Traxler G. (1979) Cichorium calvum Schultz Bip. ex Asch., Kahlfrüchtige Wegwarte (Zichorie) - neu für Österreich. Burgenland. Heimatbl. 41(2): 91-93.