Sambucus L.
As currently understood Sambucus is a genus of nine species confined to the temperate to subtropical regions of the world (Bolli 1994, Mabberley 2008). However, species boundaries are rather controversial and the number of species might be further reduced or expanded. Bolli l.c., for instance, reduced American elder Sambucus canadensis to subspecies rank under European elder S. nigra. However, his monographic work was not based on molecular studies and is rarely followed. The results reported by Clarke & Tobutt (2006) in their study on microsatellite primers tend to support the idea that American and European elderberries are two different species. Three species are native in large parts of Europe, including Belgium: Sambucus ebulus L., S. nigra L. and S. racemosa L. (Lambinon & Verloove 2012). All (the former perhaps less frequently so) are also cultivated as ornamentals and sometimes occur in areas where they are not originally native. Especially Sambucus racemosa has much extended its distribution area in Belgium in the past decades (Ronse 2006). At least part of these new populations are in fact garden escapes (berries dispersed by birds). In such cases non-native races or forms might be involved. However, so far no obvious morphological differences have been noticed between disjunct (for instance from several places in West-Flanders) and native populations, especially with regard to pubescence. In the British Isles an American and Asian vicariant (and many intermediate forms) have been recorded (McClintock 1982, Stace 2010a), respectively subsp. pubens (Michaux) House and subsp. sieboldiana (Miq.) Hara. Bolli (1994) merely included subsp. pubens (and others) in the variability of Sambucus racemosa. A form with deeply laciniate leaves (var. plumosa Spaeth. ex Carr., of doubtful taxonomic value) has been recorded as an escape in Belgium (Lambinon & Verloove 2012). Many records of Sambucus nigra also represent garden escapes; some of these do not correspond with the native form. The exact identity of some of these taxa should be further examined. Out of these var. laciniata L. with deeply laciniate leaf lobes is a frequent escape from cultivation (see also Helebrant 1973). A form with pale greenish to whitish, translucent berries belongs with var. nigra f. alba (Weston) Rehd. (syn.: f. chlorocarpa (Hayne) Geerinck) and has also been recorded as an escape. The same applies to var. viridis Weston, a cultivar with yellowish foliage; it has been recorded as an escape in Zwijndrecht in 1999. The nomenclature and taxonomy of these “taxa” is unresolved and most probably are of little value.
1 Herbaceous perennial, up to 150 cm tall. Stipules conspicuous and persistent, ovate with serrate margin. Anthers reddish to purplish. Petals acute at apex (native) === Sambucus ebulus
Taller shrubs or small trees. Stipules smaller, subulate or absent. Anthers yellowish. Petals rounded at apex === 2
2 Inflorescence an ovoid to globose panicle. Stipules replaced by glands. Ripe fruit always red. Petals cream-coloured. Shrub to 4 m tall (native) === S. racemosa (incl. non-native taxa)
Inflorescence a more or less flat corymb. Stipules subulate or absent. Ripe fruit purplish or black (rarely greenish or yellowish). Petals white. Small tree up to 10 m tall === 3
3 Fruits ruby-red, turning purplish (very rarely greenish or yellowish). Leaflets usually 7 (5-11). Often rhizomatous. Nutlets usually 4 (3-5) === S. canadensis
Fruit green, turning purplish (very rarely remaining greenish or yellowish). Leaflets usually 5 (5-7). Not rhizomatous. Nutlets usually 3 (rarely 4) (native) === S. nigra (incl. non-native taxa)
Literature:
Bolli R. (1994) Revision of the genus Sambucus. Diss. Bot. 223: 1-227.
Cann D.C.G. (2000) Sambucus. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 416-418.
Charlebois D., Byers P.L., Finn C.E. & Thomas A.L. (2010) Elderberry: Botany, Horticulture, Potential. Horticultural Reviews 37: 213-280. [available online at: http://naldc.nal.usda.gov/download/47014/PDF]
Clarke J.B. & Tobutt K.R. (2006) Development of microsatellite primers and two multiplex polymerase chain reactions for the common elder (Sambucus nigra). Molecular Ecology Notes 6(2): 453-455.
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.
Eriksson T. & Donoghue M.J. (1997) Phylogenetic Relationships of Sambucus and Adoxa (Adoxoideae, Adoxaceae) Based on Nuclear Ribosomal ITS Sequences and Preliminary Morphological Data. Syst. Bot. 22(3): 555-573. [available online at: http://www.jstor.org/discover/10.2307/2419828?uid=3737592&uid=2129&uid=2&uid=70&uid=4&sid=21101672111237]
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Helebrant L. (1973) Laciniate Kulturvarietäten der Gattung Sambucus. Mitt. Deutsch. Dendrol. Ges. 66: 173-175.
Knowles E. (1967) Cultivars of British wild plants, 12. Elders and Viburums. Gard. Chron., Ser. 3 161(25): 14.
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Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.
Ronse A. (2006) Sambucus racemosa. 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: 795.
Schwerin F. (1920) Revisio generis Sambucus. Mitt. Deutsch. Dendrol. Ges. 29: 194-231.
Stace C. (2010a) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Stace C.A. (2010b) Classification by molecules: What’s in it for field botanists ? Watsonia 28(2): 103-122. [available online at: http://archive.bsbi.org.uk/Wats28p103.pdf]
Van der Meijden R. (2005) Heukels’ Flora van Nederland (23e druk). Wolters-Noordhoff, Groningen: 685 p.