Rhamnaceae

The Rhamnaceae family is a nearly cosmopolitan and large family with almost 1,000 species (Mabberley 2008). The family counts two native genera in Belgium, each with a single species (Lambinon & Verloove 2012): Frangula alnus Mill. and Rhamnus cathartica L. Both species produce berries that are frequently eaten by birds. Frangula alnus always has been a rather common and very widespread species in Belgium (Van den Bremt 2006). Rhamnus cathartica, on the contrary, was initially confined to calcareous soils in parts of Wallonia. However, in the past decades it increasingly escaped from plantations (possibly coinciding with a slight natural expansion) and now occurs in areas where it is not originally native, for instance in coastal dunes (Van Landuyt 2006).

Numerous other species, from these and other genera, are cultivated as ornamentals (see Cullen & al. 1997 for a useful account for Europe). Some of these ornamentals have been recorded as escape in Belgium.

1. Stipules stout and persistent, spinescent === Ziziphus

1. Stipules soft, often caducous, never spinescent (but branches sometimes ending in a spine) === 2

2. Flowers blue or (more rarely) white. Shrub ca. 100 cm === Ceanothus

2. Flowers yellowish green or greenish yellow. Small tree up to 600 cm === 3

3. Leaves with entire margins (native) === Frangula

3. Leaves with serrate margins === Rhamnus

Additional alien: Paliurus spina-christi Mill. (Medit., SE-Eur., garden escape).

References

Cullen J. & al. (eds.) (1997) Rhamnaceae. In: The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 184-194.

Lambinon J. & Verloove F. (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.

Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.

Van den Bremt P. (2006) Frangula alnus. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 409.

Van Landuyt W. (2006) Rhamnus cathartica. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 745.