Galium divaricatum Pourr. ex Lam. [syn.: G. parisiense L. subsp. divaricatum (Pourr. ex Lam.) Rouy & Camus] (Medit.) – A very rare and ephemeral alien. Already collected in the 19th century (without further details). In 2008 Galium divaricatum was observed on a coal mining spoil heap in Eisden. Although found growing in a suitable habitat (sun-exposed, bare gravelly area) it was not confirmed subsequently.
Galium divaricatum is much reminiscent of G. parisiense and some (also recent) authors subsume it under the latter, at subspecies rank (e.g. Ortega Olivencia & Devesa 2007). It has much longer peduncles and hence a laxer inflorescence. Its mericarps can be either smooth (G. divaricatum s.str.) or bristly (G. parisiense subsp. divaricatum var. trichocarpum Tausch).
Selected literature:
Castaner D. (1982) Galium divaricatum (Rubiaceae), new to Missouri. Sida 9(4): 368-369.
Lipscomb B.L. & Nesom G.L. (2007) Galium anglicum (Rubiaceae) new for Texas and notes on the taxonomy of the G. parisiense/divaricatum complex. Journal of the Botanical Research Institute of Texas 1(2): 1269-1276. [available online at: http://www.texasnonnatives.org/Galium_parisiense.pdf]
Ortega Olivencia A. & Devesa J.A. (2000) Galium. In: Devesa J.A. & al. (eds.), Flora Iberica, vol. 15. Real Jardín Botánico, Madrid: 56-162. [available online at: http://www.floraiberica.es/floraiberica/texto/pdfs/15_154_08_Galium.pdf]