Chenopodiaceae—Goosefoot family A Atriplex L. saltbush Susan E. Meyer Dr. Meyer is a research plant ecologist at the USDA Forest Service’s Rocky Mountain Research Station, Shrub Sciences Laboratory, Provo, Utah Growth habit, occurrence, and use. The genus Shrubby saltbush species are extremely important as for- Atriplex L.—saltbush—is cosmopolitan in distribution and age plants for livestock and wildlife in arid and semiarid comprises about 250 species of annual and perennial herbs, regions worldwide (Goodall 1982). They provide palatable subshrubs, and shrubs (McArthur and Sanderson 1984). and nutritious feed on a year-round basis and are especially Most species are halophytic (at least to some degree) and important on winter ranges. As a consequence, they have occupy salt desert, coastal strand, or saltmarsh habitats. been studied and used in range rehabilitation far more exten- Shrubby species are important in arid and semiarid regions sively than most other shrubs (Jones 1970; McArthur and throughout the world, with centers of diversity in south cen- Monsen in press; Osmond and others 1980; Tiedemann and tral Asia, Australia, temperate South America, and western others 1984). There is also considerable interest in utilizing North America. Western North America is an area of partic- saltbush species as irrigated forage crops on marginal, salin- ularly high genetic diversity, with more than 20 principal ized agricultural land (Glenn and others 1992; Watson and species of shrubs and subshrubs as well as countless hybrids O’Leary 1993). Some shrubby saltbush species are also used and variants; 12 of these species are described here (table 1). extensively for the stabilization of drastically disturbed land The genus is in a state of active evolution in the Inter- because of their ability to establish and grow on harsh sites. mountain region (Stutz 1978, 1984). The drying up of Geographic races and hybrids. An important feature Pleistocene lakes 10,000 or so years ago opened up vast of infraspecific variation in many saltbush species is the areas of unexploited salt-desert habitat. Shrubby saltbush presence of series of races at different ploidy levels species migrated in rapidly from several directions and (Sanderson and others 1990; Stutz 1978; Stutz and hybridized freely, giving rise to the rich complex of forms in Sanderson 1979). Polyploid races often show dwarfing and the region today. adaptation to extremely harsh environments. The tendency In terms of areal extent, the most important species are to evolve polyploid races has also been important in facili- probably shadscale and Gardner saltbushes (Blauer and oth- tating the formation and stabilization of interspecific ers 1976). These species are regional dominants over mil- hybrids. Saltbush species possess a wealth of genetic vari- lions of hectares in the Intermountain and northwestern ability, both within and among ploidy levels for numerous Great Plains regions, respectively. Shadscale saltbush mostly traits that may be important for survival both of local popu- occurs with winterfat (Krascheninnikovia lanata (Pursh) lations in nature and of the products of artificial seedings. Guldenstaedt.); budsage (Artemesia spinescens D.C. Eaton); Hybrid forms, even those that have not yet formed stabilized and other salt-desert shrubs, whereas Gardner saltbush is populations in nature, may possess attributes that make them able to maintain codominance with perennial grasses (Stutz useful in specific disturbed land rehabilitation applications 1978). In the Mojave Desert, desert-holly is an upland land- (Stutz 1995). scape dominant, particularly in the Death Valley region, Common garden studies with fourwing saltbush have whereas allscale saltbush is a dominant species on playa demonstrated ecotypic variation in growth form, growth fringes. Fourwing saltbush is the most widely distributed shrubby saltbush in North America and is often an important rate, winter-greenness, drought and cold hardiness, palatabil- component of grassland communities, especially in the ity, nutrient status, seed size, and seed germination and Chihuahuan Desert and western Great Plains. Sickle and establishment traits (McArthur and others 1983; Springfield basin saltbushes are inconspicuous but common components 1970; Van Epps 1975; Welch and Monsen 1981, 1984). It is of northern Intermountain salt-desert vegetation. Atriplex • 283 A 284 • Woody PlantSeedManual Woody • Table 1—Atriplex, saltbush: ecology and distribution Scientific name Common name(s) Geographic distribution Ecology A. canescens (Pursh) Nutt. fourwing saltbush, chamisa Widely distributed in W North America Wide ecological amplitude; mostly in sandy uplands & gravelly washes A. confertifolia (Torr. & Frem.) shadscale saltbush, spiny Widely distributed in W North America Wide ecological amplitude; mostly on silt S.Wats. saltbush, sheepfat or clay soils of low to moderate salinity A. corrugata S.Wats. mat saltbush Colorado Plateau N to Restricted to heavy saline clays on shale Red Desert of Wyoming outcrops A. cuneata A. Nels. Castle Valley saltbush Colorado Plateau Restricted to heavy saline clays on shale outcrops A. falcata (M.E. Jones) Standl. sickle saltbush, falcate saltbush, N Great Basin Subsaline soils of benches & alluvial fans Nuttall saltbush A. gardneri (Moq.) D. Dietr. Gardner saltbush NW Great Plains,Wyoming, & Montana Mostly on saline or subsaline clay soils A. hymenelytra (Torr.) S.Wats. desert-holly Mojave Desert Clay flats & gravelly fans under extreme aridity A. lentiformis (Torr.) S.Wats. big saltbush, quailbush, lensscale Mojave Desert; cismontane & Mostly around saline springs & seeps coastal California A. obovata Moq. mound saltbush, broadscale saltbush Chihuahuan Desert Saline flats A. polycarpa (Torr.) S.Wats. allscale saltbush, cattle saltbush, Mojave Desert; Central Valley Saline & subsaline slopes & flats desert saltbush of California A. semibaccata R. Br. Australian saltbush, trailing saltbush Introduced from Australia Along roadsides & in saline disturbances A. tridentata Kuntze basin saltbush, trident saltbush NE Great Basin, & Uinta Basin of Utah Saline flats Sources: Ansley and Abernathy (1985), Meyer (1996), Mikhail and others (1992),Young and others (1980). likely that other widely distributed saltbush species possess Figure 1—Atriplex, saltbush: bract-enclosed utricles A similar ecotypic differentiation. Many researchers who have (“fruits”) of; A. canescens, fourwing saltbush (top), A. confer- tifolia, shadscale saltbush (middle); and A. falcata, sickle salt- studied saltbush establishment from artificial seedings bush (bottom). emphasize the importance of using not just adapted species, but locally adapted ecotypes of these species (Bleak and others 1965; McArthur and others 2004; Nord and others 1971; Plummer and others 1968; Springfield 1970). Cultivar development for saltbush has also emphasized ecotypic adaptation. The 3 released cultivars of fourwing saltbush were developed for warm winter (‘Marana’), inter- mountain cold desert (‘Rincon’), and northwestern Great Plains (‘Wytana’) planting applications (Carlson 1984). ‘Wytana’ was developed from a fourwing saltbush × Gardner saltbush hybrid entity known as Atriplex aptera A. Nels. Flowering and fruiting. The flowers of saltbush are yellowish or brownish, inconspicuous, and unisexual, and are borne in the axils of the upper leaves or in terminal spikes. The male flowers consist of groups of stamens with- (figure 1). The bracteoles are not fused to the utricle, but in in a shallow 5-toothed calyx; petals are absent. Both petals native species they usually enclose it so completely that and calyx are absent in the female flowers. The naked 1- threshing is not possible. In Australian saltbush, the bracte- seeded ovary is borne instead between 2 leaflike bracteoles. oles are not fused across the top and the utricles may be Most native shrubby saltbush species are dioecious, that threshed free (figure 2) (Foiles 1974). is, the sexes are borne on separate plants. Fourwing saltbush The saltbush seed itself is contained within the utricle possesses a unique gender system known as trioecy, with and is generally not separable from it (figure 3). The disk- genetically male plants, genetically female plants, and a shaped seed has a curved embryo on its outer perimeter and third category that can switch sexes depending on environ- a scanty provision of storage tissue (in this case perisperm) mental conditions (McArthur and others 1992). Australian in the center. In most native species, the ovule (and thus the saltbush is monoecious, that is, the flowers are unisexual seed) is inverted within the fruit, meaning that the radicle and both sexes are present on the same plant. end points upward. This facilitates radicle emergence from Saltbush species flower in early to late summer, and between the bracteoles, which often have their only opening fruits ripen from early fall to winter. The flowers are wind- or weakest point at the tip. The degree of woody thickening pollinated. The leaflike bracteoles stay green and photosyn- of the bracteole walls varies among and within species and thetically active until quite late in the ripening process and may be linked to the persistent seed dormancy often encoun- probably provide resources directly to the ripening ovule tered. within. The fruits often persist on the bushes at least until Seed collection, cleaning and storage. Saltbush seeds spring, and it is not uncommon to find 2 generations of are harvested by stripping