Tanacetum L.
(incl. Balsamita Mill.)
Tanacetum is a genus of ca. 154-160 species (Oberprieler & al. 2007, Mabberley 2008). Most species are confined to the temperate regions of the Old World (predominantly Eurasia, some also in North America and North Africa). Only one species, Tanacetum vulgare L., is native in Belgium (Lambinon & al. 2004). Numerous species are widely cultivated as ornamentals (see Cullen 2000 and Jäger & al. 2008 for an up-to-date overview of the genus in cultivation in Europe).
The generic limits of Tanacetum were controversial for quite some time. It was often segregated in several smaller units (including Balsamita Mill. and Pyrethrum Zinn). Chrysanthemum, on the other hand, is obviously closely related and many species currently accommodated in Tanacetum have names in this genus as well. Recent molecular phylogenetic research somehow elucidated the circumscription of Tanacetum (Sonboli & al. 2011). Despite the high morphological diversity in the genus, sequence divergence among species of Tanacetum was found to be very low, leading to unresolved phylogenetic relationships within the genus. Nevertheless, the generic separation of Tanacetum from other members of subtribe Anthemidinae (i.e. Anthemis, Cota and Tripleurospermum) was demonstrated, while other, presently accepted genera are found nested in Tanacetum (none relevant for Belgium).
1. Basal leaves undivided, at most scalloped or toothed. Cauline leaves at most divided halfway to midrib. Ligules usually absent === Tanacetum balsamita
1. All leaves divided much more than ½ to base, pinnatifid to pinnatisect. Ligules present or absent === 2
2. Ligules absent, all florets tubular (native) === T. vulgare
2. Ligules present === 3
3. Heads very numerous (ca. 40-100) in a dense, compound corymb. Involucre 4-7 mm across. Stem up to 150 cm tall. Not strongly aromatic === T. macrophyllum
3. Heads few in a lax corymb. Involucre 6-8 mm across. Stem up to 60 cm tall. Strongly aromatic === T. parthenium
Additional alien: Tanacetum corymbosum (L.) Schultz-Bip. (syn.: Chrysanthemum corymbosum L., Pyrethrum corymbosum (L.) Scop.) (C-Eur. and W-As., garden escape). Tanacetum coccineum (Willd.) Grierson was accepted by Verloove (2006a) but the only Belgian record turned out to be referable to a cultivated plant.
Literature:
Bremer K. & Humphries C.J. (1993) Generic monograph of the Asteraceae-Anthemideae. Bull. Nat. Hist. Mus. London (Botany) 23(2): 71-177.
Cullen J. (2000) Tanacetum. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 599-601.
Heywood V.H. (1976) Tanacetum. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 4. Cambridge University Press, Cambridge: 169-171.
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.
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.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Oberprieler C., Himmelreich S. & Vogt R. (2007) A new subtribal classification of the tribe Anthemideae (Compositae). Willdenowia 37: 89-114.
Sell P. & Murrell G. (2006) Flora of Great Britain and Ireland. Vol. 4 Campanulaceae – Asteraceae. Cambridge University Press, Cambridge: XXVIII + 624 p.
Sonboli A., Stroka K., Kazempour Osaloo S. & Oberprieler Ch. (2011) Molecular phylogeny and taxonomy of Tanacetum L. (Compositae, Anthemideae) inferred from nrDNA ITS and cpDNA trnH-psbA sequence variation. Plant Syst. Evol. 297: 1-14.
Verloove F. (2006a) Catalogue of neophytes in Belgium (1800-2005). Scripta Botanica Belgica 39: 89 p.