Dianthus giganteus D’Urv. (SE-Eur.) – A very rare but possibly overlooked relic of cultivation, often persisting for some time or more or less naturalized locally. Discovered on a coal mining spoil heap (Terril du Sept) in Hornu (Le Vanneaux) in 1993 and subsequently confirmed in 2001. Although still present in 2009 less abundant by now (comm. P. Dupriez). Also introduced on several other coal mining spoil heaps in the very same area but much less persistent and gone by now. A population of ‘Dianthus carthusianorum’ from grassland in Kooigem (2009) obviously also belongs here (waarnemingen.be). In 2010 furthermore discovered on coalmining spoil heaps in the surroundings of Charleroi (Souvret and Roux). At least in the former locality exceedingly common and apparently well-established since quite some time (see also: http://alienplantsbelgium.be/content/dianthus-giganteus-belgium-lookalike-native-d-carthusianorum). Dianthus giganteus grows on dry, gravelly substrate on sun-exposed habitats.
The cultivated plant belongs to the tall and robust subsp. giganteus. This species is much reminiscent of native Dianthus carthusianorum and long confused with it in Belgium. Records of the latter in non-natural habitats (canal- and road banks, coal mine heaps, etc.) are suspect and require careful examination. Dianthus giganteus is a much taller species (easily reaching 100 cm), with many-flowered heads and hence much more attractive. Moreover, it has acuminate epicalyx scales. Dianthus carthusianorum, on the contrary, rarely exceeds 50 cm, has rather few flowers per head and epicalyx scales that are very abruptly narrowed at apex.
Another related species, Dianthus cruentus Griseb., is possibly overlooked (see Kurtto 2001). In stature it even more closely resembles Dianthus carthusianorum but its petals are usually smaller and calyx and epicalyx are slightly puberulous. A similar plant was once recorded in Brussels (without further details).
Dickoré W.B., Lewejohann K. & Urner R. (2012) Neufunde, Bestätigungen und Verluste in der Flora von Göttingen (Süd-Niedersachsen). Florist. Rundbriefe 42: 5-59.
Frank D. & John H. (2007) Bunte Blumenwiesen – Erhöhung der Biodiversität oder Verstoss gegen Naturschutzrecht? Mitt. florist. Kart. Sachsen-Anhalt 12: 31-45. [available online at: http://bv-st.de/images/Flo-Kart_2007_031-045_Frank_John.pdf]
Kiesewetter H. & Henker H. (2010) Die Etablierung neuer Taxa an Autobahnen und anderen Verkehrswegen in Mecklenburg-Vorpommern. Bot. Rundbr. Mecklenburg-Vorpommern 46: 33-42.
Kurtto A. (2001) Caryophyllaceae. In: Jonsell B. (ed.), Flora Nordica, vol. 2. The Bergius Foundation, Stockholm: 83-216.
Sonnberger B. (2005) Dianthus giganteus D'Urv. - ein verkannter Neophyt in Bayern? Ber. Bayer. Bot. Ges. 75: 184-185. [available online at: http://www.bbgev.de/berichte/075_2005/bot_kurzberichte.pdf]