Tamarix L.
Tamarix is a taxonomically very complex genus of 54 species, mostly native in temperate Eurasia and the Mediterranean area. None is native in Belgium. Tamarix is frequently introduced outside its native distribution range: as an ornamental in gardens or public plantations or, more often, as a windbreak (for instance in coastal dunes) or for erosion control. They are easily grown and tolerant of poor soils. Several species are reputed environmental weeds, especially in the United States and Australia.
Despite the existence of a fairly recent monograph of the genus (Baum 1978) Tamarix remains an exceedingly complex genus. Most species cannot be identified without flowers and intermediate states exist for several morphological characters (and can even vary on a single individual or from season to season). Furthermore, hybridization plays a role in the taxonomic confusion (e.g. Mayonde & al. 2015). Finally, DNA sequence data are in part incongruent with morphological distinctions currently used to segregate taxa (Gaskin 2003, Gaskin & Schaal 2002, 2003). The most recent molecular phylogenetic study of the genus, based on a combination of nuclear and plastid DNA sequences, shed some new light on species boundaries and relationships (Villar & al. 2019).
The representatives of Tamarix in Belgium belong to two difficult groups. The populations with 4-merous flowers belong to the Tamarix parviflora / tetrandra group, those with 5-merous flowers to the T. africana / canariensis / gallica group. The exact identity of each population should be checked. In Belgium Tamarix mostly occurs in (semi-)natural habitats (seadunes). It was chiefly planted in situ in the past but, fortunately, hardly reproduces. Saplings probably have not been observed so far. More or less remote bushes probably arose from removed rhizomes.
- Flowers mostly 5-merous. Anthesis chiefly aestival (but sometimes also flowering in April), racemes produced on current year’s growth === Tamarix gallica
- Flowers mostly 4-merous. Anthesis exclusively vernal, racemes produced on previous year’s growth === T. parviflora
References:
Baum B.R. (1967a) Introduced and naturalised tamarisks in the United States and Canada. Baileya 15: 19-25.
Baum B.R. (1967b) Tamarix. In: Davis P.H. (ed.), Flora of Turkey, vol. 2. Edinburgh University Press, Edinburgh: 349-351.
Baum B.R. (1978) The genus Tamarix. Israel Academy of Sciences and Humanities, Jerusalem: IX + 209 p.
Crins W.J. (1989) The Tamaricaceae of the southeastern United States. J. Arnold Arbor. 70: 403-425.
Gaskin J.F. (2003) Molecular systematics and the control of invasive plants: a case study of Tamarix (Tamaricaceae). Ann. Missouri Bot. Gard. 90: 109-118.
Gaskin J.F. (2015) Tamaricaceae. In: Flora of North America Editorial Committee (eds.), Flora of North America North of Mexico, vol. 6. Oxford University Press, New York: 413-417. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=10868]
Gaskin J.F. & Schaal B.A. (2002) Hybrid Tamarix widespread in U.S. invasion and undetected in native Asian range. P.N.A.S.99(17): 11256-11259.
Gaskin J.F. & Schaal B.A. (2003) Molecular phylogenetic investigations of U.S. invasive Tamarix. Syst. Bot. 28(1): 86-95.
Mayonde S.G., Cron G.V., Gaskin J.F. & Byrne M.J. (2015) Evidence of Tamarix hybrids in South Africa, as inferred by nuclear ITS and plastid trnS–trnG DNA sequences. South African Journal of Botany 96: 122-131. [available online at: http://www.sciencedirect.com/science/journal/02546299/96]
Qaiser M. (1983) The genus Tamarix (Tamaricaceae) in Pakistan. Iranian Journ. Bot. 2(1): 21-68.
Sher A. & Quigley M.F. (eds.) (2013) Tamarix. A Case Study of Ecological Change in the American West: XXIII + 488 p.
Shinners L.H. (1957) Saltcedars (Tamarix, Tamaricaceae) of the Soviet Union. Southwestern Naturalist 2: 48-73.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.
Verloove F. (2006) Tamarix gallica. 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: 867.
Villar J.L., Angeles Alonso M., Juan A., Gaskin J.F. & Crespo M.B. (2019) Out of the Middle East: New phylogenetic insights in the genus Tamarix (Tamaricaceae). Journal of Systematics and Evolution. doi: 10.1111/jse.12478.
Whiteley A.C. (1997) Tamarix. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 270-272.