Alcea rosea L. (syn.: Althaea rosea (L.) Cav., incl.: Alcea xcultorum Bergmans, A. pleniflora L., A. ficifolia L., A. ficifolia (L.) All. ) (SW-As.) – An increasing garden escape, especially in urban areas. Usually found at foot of walls, in ruderal areas, cracks in pavement, old walls,… Sometimes also seen on riverbanks (for instance dikes of river Maas), dumps or road- and railway banks. Initially rather ephemeral but apparently becoming naturalised now in suitable, less disturbed habitats, especially in the vicinity of Antwerpen and Gent, probably also along river Maas (see also Verloove 2002).
Alcea rosea is a very variable species, particularly with regard to flower colour and leaf shape. Plants with very dark purplish petals have been recorded (cv. 'Nigra'). The exact identity of every single population is uncertain. Plants in cultivation may be complex hybrids. The affinities of Alcea rosea itself are also obscure; it probably is a stabilised hybrid of Alcea setosa (Boiss.) Alef. and A. pallida (Willd.) Waldst. et Kit.
Alcea ficifolia, probably a hybrid of A. rosea and A. rugosa, is rather distinct in having more deeply lobed leaves and (usually) creamy flowers. It is a rare and usually ephemeral garden escape or -throw-out and possibly confused with Alcea rosea. Recently recorded on dumps or levelled soil near Boom (2002) and Izegem (2007). Persisting at a foot of a wall in the port area of Gent since 2008 (a single specimen). The taxonomic value of this taxon is possibly restricted and it is often merely reduced to synonymy under Alcea rosea (see also Webb 1968, Le Huquet 1997, Stace 2010). Alcea ficifolia is said to be much reminiscent of A. rosea (Le Huquet 1997) but some plants almost perfectly match A. rugosa as well and the specific boundaries between these taxa have become unclear. See below under Alcea rugosa for more details.
Adolphi K. (1995) Neophytische Kultur- und Anbaupflanzen als Kulturflüchtlinge des Rheinlandes. Nardus 2: 272 p.
Le Huquet J.A. (1997) Alcea. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 215.
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.
Webb D.A. (1968) Alcea. In: Tutin T.G. & al. (eds.), Flora Europaea, volume 2. Cambridge University Press, Cambridge: 253-254.