Authors: Barry Meyers-Rice, Global Invasive Species Team, The Nature Conservancy
- Tamarix aphylla is deciduous shrub that can grow up to 15 ft. (4.6 m) in height.
- Leaves are small, scale-like, gray-green in color, and overlap along the stem. The bark is smooth and reddish on younger plants, turning brown and furrowed with age.
- Small, white to pink flowers develop on 2 in. (5.1 cm) long spikes from March to September.
- Fruits are tiny capsules that have a small tuft of hair.
- Ecological Threat
- Several species are considered invasive in the United States and distinguishing the species can often be difficult. Tamarix aphylla invades streambanks, sandbars, lake margins, wetlands, moist rangelands, and saline environments. It can crowd out native riparian species, diminish early successional habitat, and reduce water tables and interferes with hydrologic process. Tamarix aphylla is native to Eurasia and Africa and was introduced into the western United States as an ornamental in the early 1800s. It occurs throughout the western and central United States, but is most problematic in the Southwest.
Of the species of Tamarix commonly used as windbreaks or in erosion control, T. aphylla (Athel Tree) is the least invasive. It is widely used in the southwest USA, and does not appear to be establishing itself as an aggressive weed species. However, stands of naturalized plants have been noticed within this range (for example near Needles, CA or Lake Havasu City, AZ). These specimens do not appear to have been planted. Reproduction is apparently vegetative only.
The behavior of Tamarix aphylla in central Australia, along the Finke River, is very different from its behavior in the USA. It was planted by settlers as a shade tree, and it appeared benign for several decades. But its behavior changed during the 1974 rainy season. After the floods the plant invaded hundreds of kilometers of riparian habitat. It is unclear why such an explosion of growth occurred. It may be the rains induced a vast discharge of water-borne seed. Perhaps the scouring flood-waters removed stretches of native Eucalyptus, and the Tamarix pioneered the newly opened habitat. A nearby system of salt pans from a paleoriver system may have contributed to the invasion by releasing salt into the river---increased salinity was measured at one of the most heavily invaded sites. The salt may have helped kill the native plants so the halophytic Tamarix could invade.
It is not known why Tamarix aphylla has such different profiles in the US and Australia. It might be the plants represent two different gene pools, and the Australian plants are simply more invasive. On the other hand, it may be that the US plants are latently invasive and need certain events in order to promote a massive bloom (which may result in more aggressive progeny). The Hawaiian plants have been in place for a few decades without invasive behavior. The Australian plants were similarly benign for several decades before the 1974 floods.
Tamarix aphylla exudes salts from its leaves which would presumably degrade the soil. Tamarix stands support far fewer arthropod vertebrate species than do native plants.
- Tesky, Julie L. 1992. Tamarix aphylla, Fire Effects Information System, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory
- Global Invasive Species Database. 2011. Invasive Species Specialist Group (ISSG) of the IUCN Species Survival Commission
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- USDA ARS GRIN
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- Neill, W. (1997) private communication.
- Wiesenborn, W. (1997) private communication.