Flora of North America species comparison

Tamarix aphylla forms hybrids (rarely) with T. ramosissima and T. chinensis.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Species ca. 54 (8 in the flora).

Tamarix has been introduced to many areas through horticultural specimens, which are still available in some areas of North America. The species commonly planted include all those treated here except T. tetragyna. The extensive use of T. parviflora in gardens throughout North America has led to an abundance of collections in herbaria, and thus the species has been reported as widespread in various works (see J. T. Kartesz and C. A. Meacham 1999). For this treatment, only naturalized plants were considered, which greatly reduced the reported distributions of some species. Additionally, many midwestern and eastern populations of Tamarix recorded from states such as Massachusetts and Missouri have not been found again for decades and are thought to no longer exist.

Identification of some Tamarix species is relatively simple based on leaf morphology (for example, leaves sheathing the stems in T. aphylla compared to sessile or amplexicaul leaves in all other species in the flora) or floral morphology (for example, four petals in T. parviflora compared to usually five in all other species in the flora). Sterile collections have led to many unidentified specimens, and the most common misidentifications are among the pentamerous species T. canariensis, T. chinensis, T. gallica, and T. ramosissima, which require careful study of the nectar disc and other minute characters. The following suggestions for dissection and clarifications of terminology may help. Soak dried flowers in hot water containing a drop of liquid soap. This will help keep parts pliable and complete during dissection. Under a dissecting scope, hold the pedicel firmly with tweezers and with other tweezers pull the pistil out of the flower. At this point, if the petals are not blocking the view, the nectar disc should be visible. Nectar disc lobes will be either confluent with the filaments (synlophic) or alternate with the filaments (hololophic) (see illustrations of T. gallica and T. ramosissima respectively). To inspect filament insertion (a character that distinguishes T. chinensis from T. ramosissima) it is necessary to remove floral parts from beneath the nectar disc and look at the lower surface of the disc. Filaments originate either from below the nectar disc, sometimes near the margin (hypodiscal insertion) or from the edge of the disc (peridiscal insertion).

Because the character states distinguishing Tamarix chinensis and T. ramosissima are at times difficult to determine and often are not satisfactorily unequivocal throughout a plant, various authors have, not unreasonably, synonymized these species in North American treatments (see S. L. Welsh et al. 1993; K. W. Allred 2002). The difficulty in distinguishing between these two species is probably due to their high rate of hybridization in North America (J. F. Gaskin and B. A. Schaal 2002). In Asia these two species were originally thought to come from overlapping regions, with T. ramosissima ranging from Turkey to Korea, and T. chinensis ranging from western China to Japan (B. R. Baum 1978). DNA sequences indicate that the two species are genetically distinct, and that there is no geographic overlap of the distinguishing genotypes, T. ramosissima being found west of central China, and T. chinensis to the east of central China. There were no hybrid combinations of these species-specific genotypes found anywhere in Asia, thus the hybrids found in North America may be novel combinations produced since their introduction (Gaskin and Schaal).

Various Tamarix species have been distributed horticulturally for their ornamental and erosion-control in basket weaving and as firewood. Tamarix mannifera Ehrenberg ex Bunge (Egypt to Jordan) is a source of “manna,” a white, resinous exudate from twigs caused by insect damage that is still collected by Bedouins in the desert.

(Discussion copyrighted by Flora of North America; reprinted with permission.)