Dianthus giganteus in Belgium, a lookalike of native D. carthusianorum

Dianthus carthusianorum is a rather rare and local native species of thermophilous grasslands and calcareous rocky slopes (Lambinon & al. 2004). It is only native in parts of Wallonia (especially river valleys) and absent from Flanders (Van Landuyt & al. 2006). Since the 1990’s Dianthus carthusianorum has been claimed from artificial habitats outside its native distribution area in Belgium. It was then mainly confined to coal mine heaps and obviously introduced on purpose (in so-called wild flower seed mixtures). Plants from such populations slightly differed from native ones in being more vigorous and having larger, multi-flowered heads. It recently became evident that these introduced plants belong to a closely related but distinct species from southeastern Europe (mainly Balkans), Dianthus giganteus d’Urv.

Dianthus giganteus is a much taller species (easily reaching 100 cm), with many-flowered heads and hence much more attractive as an ornamental. Moreover, it has acuminate epicalyx scales and its leaves may be as wide as 8 mm. 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. Its leaves are always much narrower. Both species are separated in the following couplet:

• Very robust, up to 100 cm tall. Leaves to 8 mm wide. Inflorescence many-flowered (usually much more than 4 flowers per head). Epicalyx segments gradually tapered at apex === Dianthus giganteus
• Less robust, up to 60 cm tall. Leaves to 5 mm wide, usually much less. Inflorescence few-flowered (usually with 3-4 flowers per head). Epicalyx segments cuspidate at apex (native) === D. carthusianorum

In Belgium Dianthus giganteus has been recorded since at least 1993 from coal mine heaps in the surroundings of Mons. In Hornu (Terril du Sept) it is still present now although less abundant than it used to be. On other coal mine heaps in this area it probably disappeared now (comm. Pascal Dupriez). In 2010 Dianthus giganteus was furthermore discovered in the surroundings of Charleroi. It is exceedingly common and very well-established in Souvret (terril Puits Périer and terril Bois de Rianwé). In the first locality it grows along with Dianthus carthusianorum. Dianthus giganteus is frequently accompanied by Centaurea scabiosa (an introduced race), Lotus corniculatus var. sativus, Medicago sativus, Sanguisorba minor subsp. balearica, … Sometimes also by Anthyllis vulneraria subsp. balearica, Securigera varia, ….

Elsewhere in Europe Dianthus giganteus now occurs in similar habitats in Germany (Sonnberger 2005, Frank & John 2007). Before, it was already reported as a garden escape in northern Europe (Kurtto 2001). Frank & John l.c. provide an excellent, illustrated overview of potentially overlooked taxa in wild flower seed mixtures in Germany.

Both species are much alike and possibly confused elsewhere in Belgium (and beyond). Records of Dianthus carthusianorum from non-natural habitats (canal- and road banks, coal mine heaps,…) are suspect and require careful examination.

Dianthus giganteus seems to be very persisting and abundantly self-seeds. Like Coreopsis lanceolata and Linum austriacum in Flanders (Verloove 2002) it eventually managed to become a permanent member of the thermophilous vegetation on some coal mine heaps. It should be looked for elsewhere, especially on coal mine heaps, newly sown canal and road banks, etc. Critical plants may be send to the author.

References

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: ….

Kurtto A. (2001) Caryophyllaceae. In: Jonsell B. (ed.), Flora Nordica, vol. 2. The Bergius Foundation, Stockholm: 83-216.

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.

Sonnberger B. (2005) Dianthus giganteus D'Urv. - ein verkannter Neophyt in Bayern? Ber. Bayer. Bot. Ges. 75: 184-185.

Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D. (2006) Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 1007 p.

Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.