Symphoricarpos is a genus of about 18 species, primarily from North America and some from China. It is popular in cultivation and frequently planted in hedges or for ground cover. Specific boundaries have often become obscure as a result of selection and hybridization. Hence, Symphoricarpos is a taxonomically difficult genus and most plants are hardly identifiable using traditional flora's. Hoffman (2012) proposed to group all taxa in three informal groups: a 'White Berry Group' (for all taxa related to S. albus), a 'Pink Berry Group' (for all taxa related to S. xdoorenbosii) and a 'Groundcover Group' (for all taxa related to S. xchenaultii). Nowadays, complex artificial hybrids with pinkish berries and smaller leaves are more frequently planted than Symphoricarpos albus. These will probably increasingly escape and become naturalized.
As a rule, Symphoricarpos is very poorly known in Belgium (except the easily distinguished S. albus) and hardly represented in herbaria. A better understanding of the genus in Belgium surely requires further study.
1. Stem and leaves (almost) glabrous. Most leaves more than 40 mm long, those on sterile shoots very often deeply lobed. Fruit pure white, 8-15 mm in diameter === Symphoricarpos albus var. laevigatus
1. Stem and leaves (lowerside) finely pubescent. Most leaves less than 40 mm long. Fruit at least in part pinkish (never pure white), 6-10 mm in diameter === 2
2. Flowers predominantly in pairs in leaf axils (rarely a few in terminal spikes). Fruit unicoloured, purplish red === S. orbiculatus
2. Flowers predominantly in short terminal spikes (rarely a few in axillary pairs). Fruit always bicoloured, white and pink === 3
3. Largest leaves 10-20 mm long, all more or less alike. Fruit pink with white spots or white with pink spots === S. xchenaultii
3. Largest leaves 20-40 mm long, often very dissimilar on a single plant. Fruit with one side white, the other pink (not spotted) === S. x doorenbosii
Literature
Bell C.D. (2010) Towards a species level phylogeny of Symphoricarpos (Caprifoliaceae), based on nuclear and chloroplast DNA. Syst. Bot. 35(2): 442-450.
Cullen J. (2000) Symphoricarpos. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 429-430.
Hoffman M.H.A. (2012) Symphoricarpos – sortimentsonderzoek en keuringsrapport. Dendroflora 49: 66-101.
Jones G.N. (1940) A monograph of the genus Symphoricarpos. J. Arnold Arbor. 21: 201-252.
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.