Buxaceae
Buxaceae only counts one native species, Buxus sempervirens L. It is commonly found on thermophilous rocks in the valley of river Meuse (Lambinon & Verloove 2012). It is furthermore widely cultivated as an ornamental and is increasingly seen as an escape or as a relic of cultivation outside its natural distribution range (for instance a young specimen on a coal mining spoil heap in Genk, Klaverberg in 2010). However, since several species of Buxus are cultivated as ornamentals in Belgium, the identity of such plants should be critically assessed. A second genus from the Buxaceae family, Pachysandra, is widely cultivated for ornament and is often recorded as an escape from cultivation, also in Belgium.
A useful overview of the Buxaceae family in Belgium is provided by De Langhe (2013-2014). See also De Koning & al. (2000) and Roloff & Bärtels (2006).
1 Prostrate, creeping herbaceous plant. Leaves toothed, more or less alternate (or spirally arranged at the end) === Pachysandra
Erect shrub. Leaves entire, opposite (native) === Buxus
Literature
De Koning J., Van den Broek J.W., Van de Laar H.J. & Fortgens G. (2000) Nederlandse dendrologie (13e druk). H. Veenman & zonen, Ede: 585 p.
De Langhe J. (2013-2014) Buxaceae. Vegetative key to cultivated species. Ghent University Botanical Garden: 6 p. [available online at: http://www.arboretumwespelaar.be/userfiles/file/pdf/Key_BUXACEAE_JDL.pdf]
Lambinon J. & Verloove F. (avec coll. Delvosalle L., Toussaint B., Geerinck D., Hoste I., Van Rossum F., Cornier B., Schumacker R., Vanderpoorten A. & Vannerom H.) (2012) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Sixième édition. Jardin botanique national de Belgique, Meise: CXXXIX + 1195 p.
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.
Von Balthazar M., Endress P.K. & Qui Y.L. (2000) Phylogenetic relationships in Buxaceae based on nuclear internal transcribed spacers and plastid ndhF sequences. Int. J. Pl. Sci. 161(5): 785-792.
Von Balthazar M. & Endress P.K. (2002) Development of inflorescences and flowers in Buxaceae and the problem of perianth interpretation. Int. J. Pl. Sci. 163(6): 847-876.
Von Balthazar M. & Endress P.K. (2002) Reproductive structures and systematics of Buxaceae. Bot. J. Linn. Soc. 140(3): 193-228.