Aesculus is a genus with 13 species in Asia and North America (with a single species, A. hippocastanum, extending to southeastern Europe). Most of the species and several hybrids are planted as ornamentals (e.g. Edmondson 1997, De Koning & al. 2000, Roloff & Bärtels 2006). At least four of these have been recorded as escapes from cultivation in Belgium. An additional species (or perhaps rather a fertile hybrid), A. carnea J. Zeyh., is much planted but has not been recorded yet as an escape. Other species may also have been overlooked, for instance the widely grown A. turbinata Blume, a species reminiscent of A. hippocastanum but with spineless fruits and a smaller inflorescence.
1 Tall trees. Flowers white or cream tinged with yellow or red === 2
Shrubs, not exceeding 4-5 m in height. Flowers pure with or red === 3
3 Shrub with many stems, with spreading suckering growth. Flowers pure white, with long-projecting stamens. Leaflets grey-felted beneath === A. parviflora
Shrub with a single erect stem, not suckering. Flowers red, sometimes yellow at first, stamens not long-projecting. Leaflets hairless to sparsely hairy beneath === A. pavia
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.
Edmondson J.R. (1997) Aesculus. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 155-157.
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.