1. Cirsium heterophyllum (L.) Hill (syn.: Carduus heterophyllus L.) (Eur., Siberia) – An exceptional escape from cultivation. Formerly naturalised in the Kapucijnenbos at Tervuren (Arboretum), at least between 1918 and 1964. Not confirmed recently and probably gone now. Naturalised populations were furthermore discovered in the 1960’s in the surroundings of Saint-Hubert and near Konzen (Delvosalle 1966). In Saint-Hubert Cirsium heterophyllum was confirmed in 2010 (ca. 15 plants in a roadside) but obviously in a different locality (close to the local airport while it was formerly found southwest of the village).
Cirsium heterophyllum is here accepted in a narrow sense. It has long been confused with Cirsium helenioides (L.) Hill., a species that is restricted to parts of the former USSR in Europe.
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Selected literature:
Delvosalle L. (1966) A propos de Cirsium tuberosum (L.) All. et de quelques autres Cirsium hygrophiles. Nat. Mosana 19(4): 71-73.
Dickson J.H. & Walker A. (1981) What it the Scottish thistle? Glasgow Nat. 20: 101-121.
Hanelt P. (1975) Cirsium helenioides (L.) Hill - eine neue Art der Flora des Harzes. Naturk. Jahresber. Mus. Heineanum 10: 5-9.
Reif A. & Weiskopf A. (1988) Ökologische Untersuchungen an der Verschiedenblättrigen Kratzdistel (Cirsium helenioides [L.] Hill) in Oberfranken. Teil I: Vergesellschaftung und Standort. Tuexenia 8: 101-148.
Romstöck M. (1988) Ökologische Untersuchungen an der Verschiedenblättrigen Kratzdistel (Cirsium helenioides [L.] Hill) in Oberfranken. Teil III: Cirsium helenioides-Blütenköpfe und ihr assoziierter Insektenkomplex. Tuexenia 8: 163-179.
Weiskopf A., Romstöck M., Reif A. & Schulze E.D. (1988) Ökologische Untersuchungen an der Verschiedenblättrigen Kratzdistel (Cirsium helenioides [L. Hill) in Oberfranken. Teil II: Heterophyllie und Standort. Tuexenia 8: 149-161.