Valeriana is a genus of ca. 200 species mainly distributed in the northern hemisphere (some species in South Africa and South America). Three species (taxonomical rang somewhate controversial) are native in Belgium: Valeriana dioica L., V. repens Host and V. wallrothii Kreyer. According to Gardner & Richardson (2000) eight species are cultivated as ornamentals in Europe (see also Jäger & al. 2008). Some of these much resemble Valeriana officinalis (for instance V. phu) and might have been overlooked. Infraspecific, non-native taxa of Valeriana officinalis are possibly also neglected.
1. Basal leaves pinnate (native) === Valeriana repens and V. wallrothii
1. Basal leaves not pinnate === 2
2. Stolons absent. Plant up to 120 cm tall. Basal leaves deeply toothed. Upper cauline leaves with 1 or 2 pairs of lateral leaflets === 1. Valeriana pyrenaica
2. Stolons present. Plant up to 40(-60) cm tall. Basal leaves entire. Upper cauline leaves pinnatifid (native) === V. dioica
Additional alien: Valeriana phu L. (Turkey, garden escape).
Literature
Gardner M.F. & Richardson J.E. (2000) Valeriana. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 454-455.
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Jäger E.J. & Werner K. (eds.) (2005) Rothmaler Band 4. Exkursionsflora von Deutschland. Gefässpflanzen: Kritischer Band. Springer Verlag, Berlin: 880 p.
Jones G.N. (1940) A monograph of the genus Symphoricarpos. J. Arnold Arbor. 21: 201-252.
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H. (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.
Larsen B.B. (1986) A taxonomic revision of Phyllactis and Valeriana sect. Bracteata (Valerianaceae). Nord. Journ. Bot. 6: 427-446.
Ockendon D.J. (1976) Valeriana. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 4. Cambridge University Press, Cambridge: 52-55.