Buddleja L.
As currently understood (Norman in prep.) Buddleja is a genus of about 100 species, originally confined to tropical and subtropical areas in America, Africa and Asia. Molecular studies will probably help clarifying the boundaries of the genus. Species with berries rather than capsules or species with long-exerted filaments possibly belong in segregate genera. Some first studies based on molecular data, however, propose to accept a single genus with a broadened circumscription (Chau & al. 2017). These authors also present a revised classification of Buddleja.
At least 26 species (and some additional hybrids) are cultivated as ornamentals in Europe (Richardson 2000) although rather few are widespread in cultivation. Many also are frost-sensitive and require at least a warm-temperate climate. Useful accounts for western Europe are provided by de Koning & al. (2000) and Roloff & Bärtels (2006). Probably not more than 5 or 6 species are cultivated in Belgium. Most of the hardy species originate in eastern Asia.
Up to present only two species have been reliably recorded in Belgium (Buddleja albiflora and B. davidii). At least one additional species with yellow flowers was recently recorded in coastal dunes (Oostduinkerke; pers. comm. M. Leten). This record most likely refers to Buddleja globosa Hope or its hybrid with B. davidii, B. xweyeriana Weyer but requires confirmation. Both have been recorded as escapes in the British Isles (Stace 2010). Another species, Buddleja alternifolia Maxim., seems to be a rare but regular escape in several different European countries (e.g. Skalická 2000, Sell & Murrell 2009). It superficially looks like Buddleja davidii but its leaves are alternate and its flowers are borne in globose clusters on previous year’s wood. It may have been overlooked.
Buddleja was formerly included in Buddlejaceae (a monogeneric family) or in Loganiaceae. Molecular phylogenetic studies demonstrated that it should be included in Scrophulariaceae (Olmstead & al. 2001, APG III 2009).
Additional alien: Buddleja albiflora Hemsley (China, garden escape).
Literature:
APG III (2009) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants. APG III. Bot. J. Linn. Soc. 161(2): 105-121.
Chau J.H., O'Leary N., Sun W.-B. & Olmstead R.G. (2017) Phylogenetic relationships in tribe Buddlejeae (Scrophulariaceae) based on multiple nuclear and plastid markers. Bot. J. Linn. Soc. 184(2): 137-166. [available online at: https://academic.oup.com/botlinnean/article/184/2/137/3865471/Phylogenet...
Compton J. (1984) Some uncommon buddlejas. Garden (London) 109(2): 82-83.
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.
Devonport S. (1983) Some uncommon Buddlejas. Garden (London) 108(4): 156.
Gorer R. (1982) Beyond the simple butterfly bush: Buddleias for garden and greenhouse. Country Life 172 (4433): 398-402.
Grootendorst H.J. (1972) Buddleja. Dendroflora 9: 38-42.
Leeuwenberg A.J.M. (1975) The Loganiaceae of Africa: 13. Buddleja L.: 1. Acta Bot. Neerl. 24(1): 83-86.
Leeuwenberg A. J. M. (1979) The Loganiaceae of Africa: 18 Buddleja L. 2: Revision of the African & Asiatic species. Mededelingen Landbouwhogeschool Wageningen, Netherlands.
Li P. (1982) A study of the genus Buddleja L. of China (in Chinese). Acta. Bot. Yunnanica 4(3): 227-240.
Li P.T. & Leeuwenberg A.J.M. (1996) Loganiaceae. In: Wu Z. & Raven P. (eds.), Flora of China, vol. 15. Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis, USA: 327-337. [available online at: http://flora.huh.harvard.edu/china/PDF/PDF15/buddleja.pdf]
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Maunder M. (1987) Notes on tender species of Buddleja. Plantsman 9(2): 64-80.
Norman E. (2000) Buddlejaceae. In: Organization for Flora Neotropica (ed.), Flora Neotropica, vol. 81. New York Botanical Garden, USA: 1-225.
Norman E. (in prep.) Buddlejaceae. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 17. Oxford University Press, New York-Oxford.
Olmstead R.G., dePamphilis C.W., Wolfe A.D., Young N.D., Elisons W.J. & Reeves A. (2001) Disintegration of the Scrophulariaceae. Am. J. Bot. 88: 348-361. [available on line at: http://www.amjbot.org/content/88/2/348.full.pdf+html]
Richardson J.E. (2000) Buddleja. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 267-272.
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.
Sanders C. (2012) The air’s buzzing with buddleias. The Garden 9/2012: 56-60.
Sell P. & Murrell G. (2009) Flora of Great Britain and Ireland. Vol. 3 Mimosaceae – Lentibulariaceae. Cambridge University Press, Cambridge: XXVIII + 595 p.
Skalická A. (2000) Buddlejaceae. In: Slavík B. (ed.), Kvĕtena České Republiky, vol. 6. Academia, Praha: 289-291.
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Stuart D. (2006). Buddlejas. RHS Plant Collector Guide. Timber Press, Oregon, USA.
Walsh K. (1989) Buddleja in Australia: a survey. Austral. Gard. J. 8(3): 102-104.