The genus Tamarix (common name "tamarisk") contains many species (as many as 54 are formally recognized) originating from widely dispersed areas located in arid and semi-arid regions of the Old World (Baum, 1967; DeLoach, 1989). Examples are Tamarix pentandra from the Middle East, T. articulata and T. tetragyna from Israel, T. articulata-africana from the Libyan Sahara, T. aphylla, T. ericoides and T. dioica from India and Pakistan, T. chinensis, T. parviflora and T. ramosissima from southwestern Asia, T. taklamakanensis from the Sinkiang, T. gallica from Sicily and Morocco and T. gallica canariensis from the Canary Islands (DeLoach, 1989). There are no species of tamarisk native to the New World (DeLoach, 1989).
Eight tamarisk species were introduced in the U.S. in the early 1800's, mostly from Asia (DeLoach, 1989). Some were introduced for their ornamental values (e.g., T. chinensis and T. ramosissima), others for planting in wind breaks (e.g., T. aphylla) or to stabilize eroding stream banks (Neill, 1985).
While T. aphylla (a large evergreen tree often planted along railroad tracks and referred to as "athel") has invaded some riverain ecosystems in Australia (Griffin et. al., 1989), it has not acquired weedy habits in North America. This is not the case for T. chinensis, T. parviflora and T. ramosissima (small deciduous trees or shrubs often called "saltcedar") which are invasive weeds throughout the southwestern United States (Kerpez and Smith, 1987; Kunzmann et al., 1989). They have successfully invaded nearly every drainage system in arid and semi-arid areas, occupying over 607,050 hectares (Brotherson and Field, 1987), including approximately 6,475 hectares in California (Johnson, 1987). Today, saltcedar occupies suitable habitat west of the Great Plains, north into Montana and south into northwestern Mexico (DeLoach, 1989).
A first phase of the spread of saltcedar in the southwestern U.S. affected the floodplains of major drainages. By the 1940s, saltcedar had spread through extensive areas along the Gila, Salt, Pecos and Colorado River, as well as the Rio Grande (Horton, 1977). Less severe and seasonally altered flooding regimes brought about by the dams and flood control structures constructed along these rivers provided ideal conditions for the establishment, reproduction and spread of salt cedar (DeLoach, 1989; Kerpez and Smith, 1987). It is estimated that 1400 square miles of floodplain land in the western U.S. was occupied by saltcedar by 1961 (Neill, 1985). Large intermittent desert streams, such as the Mojave River near Barstow, California, have seen their original riparian vegetation of willows and cottonwoods replaced by saltcedar, but disturbances other than flood control may have favored that process. In Afton Canyon, 70% of the original native vegetation has been replaced by saltcedar, mostly since the 1960s. Reduced river flows, off-road vehicle disturbance, year-round grazing and native tree cutting are hypothesized to have contributed to that vegetation type conversion (Lovich et al., 1994).
More recently, saltcedar has expended its range into interior desert riparian habitats that are otherwise unaffected by human activities. This invasion of desert riparian areas by saltcedar has occurred fairly recently, during the last couple of decades (Lovich et al., 1994). In the Colorado Desert of southern California, Tamarix ramosissima can now be found in many of the springs (e.g., Buzzard Spring in the Eagle Mountains), streams (e.g., Palm Canyon in the Santa Rosa Mountains), and in some of the more mesic desert washes (e.g., Thousand Palm Canyon in the Coachella Valley, prior to eradication).
Baume, B.R., 1967. Introduced and naturalized tamarisks in the United States and Canada [Tamaricaceae]. Baileya 15: 19-25.
Brotherson, J.D. and D. Field, 1987. Tamarix: impacts of a successful weed. Rangelands 9(3):110-112.
DeLoach, C.J. 1989. Prospects for biological control of saltcedar (Tamarix spp.) in riparian habitats of the southwestern United States. In: Proc. Vll Int. Symp. Biol. Contr. Weeds, 1988, Rome, Italy. Delfosse, E.S. (ed.). 1st. Sper. Patol. Veg. (MAF), pp. 30714 (1989).
Griffin, G.F., Stafford, D.M., Morton, S.R., Allan, G.E. and K.A. Masters, 1989. Status and implications of the invasion of tamarisk (Tamarix aphylla) on the Finke River, Northern Territory, Australia. J. Environ. Manag. 29:297-315.
Horton, J.S., 1977. The development and perpetuation of the permanent tamarisk type in the phreatophyte zone of the southwest. USDA For. Serv. Gen. Tech. Rep., U.S. Rocky Mountain For. Range Exp. Sta. 43:124-127.
Johnson, S. 1987. Can tamarisk be controlled? Fremontia 15: 19-20.
Kerpez, T.A. and N.S. Smith, 1987. Saltcedar control for wildlife habitat improvement in the southwestern United States. USDI Fish and Wildlife Service. Res. Pub. 169, Washington, D.C.
Kunzmann, M.R., Johnson, R.R. and P.S. Bennett (eds.) 1989. Tamarisk control in the southwestern United States. USDI, National Park Service, Special Rep. No.9 (Revised 1990) 144 pp.
Lovich, J.E., Egan, T.B. and R.C. de Gouvenain, 1994. Tamarisk control on public lands in the desert of southern California: Two case studies. In: Proceedings, 46th Annual California Weed Science Society Meeting. San Jose, California.
Neill, W.M., 1985. Tamarisk. Fremontia 12(4):22-23.
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