Thalictrum speciosissimum L. (syn.: T. flavum subsp. glaucum (Desf.) Battan.) (W-Medit.) – An exceptional escape from cultivation or throw-out. A single plant was discovered in 2011 in a ditch in Kortrijk (angle of Kennedybos and E17-motorway) and subsequently regularly confirmed. A nearby area was previously leveled and an off-ramp constructed; rhizomes of many horticultural species have been transported on that occasion which probably explains the occurrence of this species. In 2014 also observed on rough ground in Tielt (a single individual), along with other garden throw-outs.
Thalictrum speciosissimum is much reminiscent of native T. flavum and sometimes given subspecies rank. We here follow Montserrat (1989) and Hand (2001) who accept it as a species distinct from the latter. In addition to the key characters (glaucous foliage with very prominent veins) the plant in Kortrijk also is much taller than Thalictrum flavum and its flowers are a brighter yellow. It is not unlikely that Thalictrum speciosissimum has been overlooked up to present. Records of Thalictrum flavum-like plants in unusual habitats (rough ground, urban habitats, etc.) are suspect and might hide records of T. speciosissimum (or other similar species, especially T. lucidum L.).
There are relatively few records of Thalictrum speciosissimum as an escape in the rest of Europe. Hand (2001) cites records from the British Isles, Germany, Norway and Sweden.
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Selected literature:
Hand R. (2001) Revision der in Europa vorkommenden Arten von Thalictrum subsectio Thalictrum (Ranunculaceae). Bot. Natursch. Hessen, Beiheft 9: 358 p. [available online at: http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/25339]
Hand R. & Schlesinger S. (1997) Ein vorkommen der west-mediterranen Wiesenraute Thalictrum speciosissimum L. in Sudbaden. Carolinea 55: 120.
Montserrat P. (1986) Thalictrum. In: Castroviejo S. & al. (eds.), Flora Iberica, vol. 1. Real Jardín Botánico, Madrid: 387-401.