Acacia greggii is known by the common names catclaw acacia, devilsclaw, gregg catclaw and longflower acacia.
Catclaw acacia is common in southern California, Arizona, western Texas, Baja California, and northern Mexico. It is less common in Nevada, Utah, and New Mexico and Colorado.
Devilsclaw is a native, long-lived, deciduous, spreading shrub or small tree. Depending on the harshness of site conditions, catclaw acacia typically ranges from 3.3 feet to 29.5 feet tall. Far from California, on the Lower Rio Grande River, catclaw acacia trees measured 35 feet. The main trunk can be 12 inches in diameter; the bark is commonly 3.2 mm thick, developing cracks and becoming scale-like with age. Catclaw acacia is heavily armed with stout, curved spines, which are three to four millimeters long, distributed along branches at the internodes.
Alternate leaves are bipinnate with 4 to 7 leaflet pairs. Leaves measure 0.8 to 2 inches long. Leaflets are between 2 and 12 mm long and are normally hairy. Catclaw acacia has extrafloral nectaries on the primary rachis that are thought to promote mutualistic interactions between catclaw acacia and insects, commonly ants. The ants provide protection from other insect herbivores, while the extrafloral nectaries provide the ant with food and water. Catclaw acacia’s legume fruits are straight to twisted, constricted between the seeds, and measure 2 to 4.7 inches long by 0.4 to 0.8 inches wide. Seeds are round and typically 5-7 mm in size. Although catclaw acacia is a legume, in controlled experiments nodulation has not occurred.
Acacia greggii is highly adapted to harsh desert conditions. A deep root system, high water use efficiency, high photosynthetic capacity, and use of the C3 photosynthetic pathway allow catclaw acacia to thrive in harsh desert climates.
The plant’s root system is a substantial one. Catclaw acacia roots are documented to have sunk to a depth of greater than 18 feet in southeastern Arizona. On a wash site in the Gold Valley of the Mohave Desert, 55 percent of the total catclaw acacia dry weight was root.
Longflower acacia is long lived. Catclaw acacia shrubs were aged from repeat photographs of Grand Canyon sites. Photographs indicate that 85 percent of the plants on the sites were at least 104 years old. Other pictures showed that 5 of 6 plants were at least 120 years old. Researchers estimated 15 percent mortality and 27 percent recruitment in 100 years from the photographs.
Catclaw acacia reproduces sexually through seed production, and when top-killed, catclaw acacia regenerates asexually through root crown sprouts.
Catclaw acacia is considered an important honey plant, and likely bees are the chief flower pollinators.
Dispersal of catclaw acacia seed can result from animal movements and abiotic disturbances. In the Chihuahuan Desert of Arizona and New Mexico, researchers found that plant material used by cactus wrens to construct nests often include seeds. One of 12 cactus wren nests contained catclaw acacia seed. Collections are commonly made greater than 65.6 feet from the nest site, indicating nest construction is a significant seed dispersal mechanism. Likely grazing animals disperse catclaw acacia seed. No studies have yet addressed seed viability once passed through the digestive tract.
Following heavy rainfall that was 76 percent of the annual average in San Diego County, 612 catclaw seedlings per hectare occurred on a site void of mature catclaw acacia. However, catclaw acacia occurred in washes upstream from the site. Most likely the storm relocated seeds from the wash to produce the catclaw acacia seedling population.
Temperature and moisture requirements must be met for catclaw acacia seed to germinate. One study by the botanist Janice Bowers suggests that August and September seed germination is triggered by 1.2 inches or more of rainfall. Another study by botanists Gilbert Jordan and Marshal Haferkamp suggest temperatures above 45 °F are required to germinate catclaw acacia seed. In the confines of Joshua Tree National Monument, catclaw acacia germinated only in August and September. However, factors other than temperature and moisture may affect germination. Even when able to control growing conditions, horticulturists were unable to germinate seed collected from plants in 1927, while seed collected in 1929 germinated.
Site conditions and early disturbances affect catclaw acacia seedling development. It has been found that seedling growth was greatest when plants were exposed to full sunlight. When defoliated early in development, catclaw acacia seedlings had significantly less total biomass than nondefoliated seedlings.
Catclaw acacia occupies dry gravelly mesas, canyons, arroyo banks, rocky hillsides, desert flats, washes, floodplains, and riparian areas in arid to semiarid southwestern regions.
Devilsclaw is present in many Mojave Desert washes, along with desert willow (Chilopsis linearis), and smoketree (Psorothamnus spinosus). Other wash scrub vegetation in the Mojave Desert includes cattle saltbrush, mesquite, Mohave rabbitbrush, white burrobrush, Schott’s pygmycedar, desert almond, and skunkbush sumac. It is also associated less often with California jointfir, stretchberry and red barberry.
In drainages and minor waterways of the desert, catclaw acacia occurs in burrobush-dominated communities with Anderson wolfberry, desertbroom, cattle saltbush, and Mohave rabbitbrush. In creosotebush-dominated communities typical in southern California, Catclaw acacia accompanies white bursage, blue paloverde and saguaro. It also populates desert microphyll woodlands together with blue paloverde, smoketree, honey mesquite, screwbean mesquite, desert lavender and creosotebush.
The climate regimes described for catclaw acacia habitats range from mild to severe. Catclaw acacia flowers from May through October in the Mojave Desert.
Catclaw acacia provides food, shelter, nesting sites, and nesting material to a host of wildlife and livestock species. Catclaw acacia browsers include deer, livestock, and rabbits. Both game and nongame bird species feed on catclaw acacia.
Indigenous people found several uses for catclaw acacia. The Akimel O’odham or Gila River Pima ate catclaw acacia seeds as “starvation food” when better foods were not available. The Cauhilla Native Americans of southern California utilized catclaw acacia wood as fuel and ate catclaw acacia beans. The pods were eaten fresh, dried, or ground into powder; the bitter taste of the pods suggests catclaw acacia was not preferred.
Catclaw acacia had medicinal properties. Pods are used to make an eyewash to treat conjunctivitis. Leaves and pods when ground into powder will stop small amounts of bleeding and soothe chafed skin or diaper rash. When this powder is made into a tea, it can be used as an antimicrobial wash or drunk to treat diarrhea and dysentery. Native Americans used catclaw acacia to soothe sore flank and back muscles of their horses. The flowers and leaves in tea can treat nausea, vomiting, and hangovers. The thick, sticky catclaw acacia root, when made into tea, treats sore throats, mouth inflammations, and coughs.
Catclaw acacia wood is strong, hard, tight grained, and heavy. It is used for cabinets, turnery, and fencing. The contrasting reddish brown heart wood and yellow sapwood makes it valuable for making souvenirs.
