Heuchera micrantha

Heuchera micrantha Lindl. (western N Am) – A rare and usually ephemeral escape from cultivation. First observed in Antwerpen (Sanderusstraat) in 2005. Rather numerous plants were found then on basement walls in an urban environment (still present in 2009 but not confirmed lately). Since then recorded in a few additional localities, mostly in urban areas (Brussels, Boom) and in small numbers. In Stekene (Stropersbos) also seen alongside a path in woodland.
Most plants seen as escapes belong to cultivars with reddish brown leaves and hypanthia that are tinged pinkish red (cv ‘Palace Purple’ or ‘Rachael’ and probably others as well), a character state not observed in wild plants of H. micrantha.
Plants here reported as Heuchera micrantha may as well (or even rather) belong to complex hybrids involving H. micrantha, H. sanguinea Engelm. and H. americana L. In the British Isles such plants have been referred to H. xbrizoides hort. ex Lemoine (Clement & Foster 1994).

Selected literature:

Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.