Invasive Plants of California's Wildland

Australian saltbush (Atriplex semibaccata) is a drought-tolerant, low-growing shrub with silvery gray evergreen foliage and small red fruit. It forms a dense groundcover that is fire retardant. The dense mat is less than one foot tall, spreading up to six feet or more across.

In California, Australian saltbush is found mostly in waste places, shrubland, or woodland below 3,280 feet (1,000 m) elevation in the Mojave and Sonoran deserts and arid parts of the South Coast, Central Coast, San Francisco Bay Area, and Central Valley as far north as Glenn County. It also inhabits coastal areas and coastal salt marshes from San Diego County to Mendocino County. Australian saltbush is especially fond of heavy saline soils, particularly areas that have been heavily grazed or disturbed. It is quick to invade newly developed lands, roadsides, coastal marshes, and the margins of cultivated fields (Halvorson et al. 1988, Hickman 1993).

Australian saltbush is native to Australia and was originally introduced to the United States as livestock forage. It was introduced to California as forage in alkaline areas, starting in Tulare County in 1901. Seeds were distributed throughout the state from there. By 1916 Australian saltbush was abundant in San Diego. By 1940 it was common on the South Coast and found infrequently inland to Imperial and San Bernardino counties and the Salinas Valley (Robbins 1940).
Australian saltbush was promoted as a groundcover in arid landscapes, for erosion control, and to attract birds. Birds eat the red, berry-like fruits and may act as a means of dispersal (Sanders, pers. comm.). The plant escaped cultivation and has become a common weed.

As a ground-spreading plant, Australian saltbush displaces native plants.

Australian saltbush reproduces by seed only. The plant flowers from April to December. Male and female flowers are borne on the same plant. Other similar Atriplex species are self-compatible and wind-pollinated, suggesting this also may be true of this plant. Seeds are produced in large numbers and are surrounded by fleshy bracts when mature (Sanders, pers. comm. 1997 ). These fleshy bracts are attractive to fruit eaters, which may help disperse the seeds. Seeds have been found in the stomach contents of foxes and lizards on Santa Cruz Island (Valido and Nogales 1994, Crooks 1994). Degree of persistence of seeds in soil and germination conditions are unknown.

This low-spreading subshrub can form mats up to four feet in diameter. It grows in full sun and requires little soil moisture (Plant Advisor 1997). Australian saltbush is believed to be short-lived (two to five years), but in favorable situations it may survive for up to ten years (Sanders 1997). It is deep-rooted (Sunset 1996). Plants will survive winter temperatures well below freezing (Plant Advisor 1997).

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Seed germination can take place on saline soils, which provides a competitive advantage over other native species (De Villiers et al. 1995). Halvorson et al. (1988) reported that Australian saltbush was one of the first species to colonize eroded lands on Santa Barbara Island.

Manual methods: Australian saltbush is easy to control by hand pulling because of its diminutive size. If it is pulled before it bears seeds, it can be effectively controlled, but any residual seed pool will remain to propagate the local population.

Although the subject has not been researched in detail, it has been observed that the larvae from pygmy blue butterflies (Brephidium exile) feed on the foliage (Sanders, pers. comm.).

Chemical control of Australian saltbush has not been reported, although chemicals that control similar species, such as kochia (Kochia scoparia) and Russian thistle (Salsola tragus), likely will work on this saltbush. Russian thistle can be controlled with dicamba, 2,4-D, and picloram plus 2,4-D at 1-1.5 fl oz/acre + 0.75 pt/acre. Picloram is currently not registered in California. Kochia can also be controlled with dicamba plus MCPA amine at label strengths. 2,4-D at 1.0 pt/acre gives good kochia control, but good spray coverage is essential because 2,4-D does not translocate readily in kochia. Treatment should be to plants less than three inches tall or large spray volumes should be used to penetrate the kochia foliage. The esters of 2,4-D generally are more effective than the amines for both weeds. MCPA is not as effective as 2,4-D in controlling either weed. However, MCPA at 1.0 pt/acre will control small kochia plants. Picloram is not effective on kochia; but control is good when combined with 2,4-D ester at 0.75 pt/acre (North Dakota State University Extension Service 1998).