Soleirolia soleirolii

Soleirolia soleirolii (Req.) Dandy (syn.: Helxine soleirolii Req.) (W Medit.) – A rare but much increasing, locally naturalized escape from cultivation. First documented in 1941 (Verloove 2006). At present it has been recorded in many of the larger cities in Flanders (e.g. Antwerp, Brugge, Gent, Leuven) and in Brussels. However, it is also known from much smaller cities and villages. It is only exceptionally observed in Wallonia so far (only known at present from the Ath area). An up-to-date overview of Belgian observations is available here: http://waarnemingen.be/soort/view/9223.
The naturalization of Soleirolia soleirolii in Belgium is a recent event. This species was not yet considered naturalized by Verloove (2002). The same trend is visible in neighbouring countries, for instance in urban habitats in the Netherlands (e.g. Denters 2004, Holverda & al. 2009).
Soleirolia soleirolii is relatively frost-sensitive (see, however, Jagel & Buch 2012) and only survives in climatologically suitable habitats. It typically occurs in damp urban habitats: as a weed in lawns and plantations, in cracks of concrete, pavements and foot of walls.
A vegetatively very similar species is grown for the same purposes: Nertera granadensis (Mutis ex L.f.) Druce. It is a species of Rubiaceae native to Australia, New Zealand and South America. It has opposite, glabrous leaves that are stipulate (see also Jagel & Buch 2012). This species has been recorded as a naturalized escape in the British Isles (Stace 2010). It has very distinct globose orangish fruits. Also very similar is Pilea microphylla (L.) Liebm. Like Soleirolia it is grown as a groundcover ornamental and readily escapes (it is a regular weed in greenhouses). It is distinguished by its opposite, glabrous leaves and multi-flowered inflorescences.

Selected literature:


Adolphi K. & Sumser H. (1991) Funde von Soleirolia soleirolii (Req.) Dandy in Deutschland. Florist. Rundbr. 25: 20-22.
Denters T. (2004) Stadsplanten. Veldgids voor de stad. Fontaine Uitgevers, ‘s-Graveland: 432 p.
Feder J. (2008) Was macht die Zimmerpflanze Bubiköpfchen in Bremer Scherrasen? Bremer Botanische Briefe 1: 11. [available online at: http://www.internetchemie.info/botanik/bbb/bremer-botanische-briefe-1.pdf]
Hauck M. (1992) Soleirolia soleirolii auch in Niedersachsen. Florist. Rundbr. 26: 54-55.
Holverda W., van Moorsel R. & Duistermaat L. (2009) Nieuwe vondsten van zeldzame planten in 2005, 2006 en ten dele 2007. Gorteria 34: 1-40. [available online at: http://www.repository.naturalis.nl/document/568057]
Jagel A. & Buch C. (2012) Soleirolia soleirolii – Bubikopf (Urticaceae), Blütenbildung auch im Freiland. Jahrb. Bochumer Bot. Ver. 3: 285-289. [available online at: http://www.botanik-bochum.de/jahrbuch/Pflanzenportraet_Soleirolia.pdf]
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.
Verloove F. (2006) Catalogue of neophytes in Belgium (1800-2005). Scripta Botanica Belgica 39: 89 p. [available online at: http://alienplantsbelgium.be/sites/alienplantsbelgium.be/files/tabel_2.pdf]

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith