©The World Botanical Associates Web Page
Prepared by Richard W. Spjut
May 2004, March 2009, Feb 2013

Larrea tridentata
Inyo Co., CA
Spjut & Casterline 15747, Mar 2004

Larrea tridentata
Inyo Co., CA
Spjut & Casterline 15747, Mar 2004

Larrea tridentata
Kern Co., Jawbone Canyon, CA
Apr 2011

Death Valley, CA
March 2009




Trees and Shrubs of Kern County (Feb 2013)

Larrea tridentata (Zygophyllum tridentatum Sessé & Mociño ex DeCandolle 1824) Coville 1893 [Excludes L. divaricata Cavanilles 1800, endemic to South America; includes L. glutinosa Engelmann 1848]. Creosote bush.  Evergreen shrub, solitary or clonal and long-lived to thousands of years, leafy near tips, with many wand-like banded (dark resinous nodes) flexuous stems from the base; bark gray; leaves opposite, resinous, aromatic, divided almost completely into two separate diverging leaflets; flowers appearing soon after rain, yellow, 5-merous with 10 stamens; gynoecium 5-carpelled, each carpel with ~6 ovules but only 1 matures (to seed), style 1, stigma 5-lobed; fruit  (camarium) appearing like a small white shaggy ball turning rusty in age, slow to break-up into its five separate indehiscent 1-seeded carpels (monocarps). Common desert shrub, southern California to southwestern Utah, Texas and to central Mexico. Type from Mexico.  Kern Co.: A dominant shrub of the Mojave Desert plains with less than 6 inches of rainfall, “covering tens of thousands of acres” (Twisselmann), occurring also in the San Joaquin Valley in Granite Canyon along Poso Creek between Woody and Bakersfield (McMinn 1939) and along Elk Hills Rd, Naval Petroleum Reserve; 207–1220 m (CCH).

Creosote bush has been treated as belonging to the South American L. divaricata Cavanilles 1800 (McMinn 1939; Munz & Keck 1959; Twisselmann 1967), or as a geographical diploid-polyploid subspecies or variety complex of that species (Felger & Lower 1970 [J. Arizona Acad. Sci. 6: 84.]; Felger et al. 2012), while others recognized the North American creosote as a separate species, L. tridentata (Jepson 1914, var. glutinosa; JM1, JM2). Laport et al. (2012) suggests their geographical disjunction and the occurrence of multiple polyploid races in North America but not South America justifies separate species status despite their low DNA sequence divergence.

Larrea includes three other species, all in South America, from which L. divaricata is distinguished by its larger flowers and hairy monocarps. The others are distinguished by their habit, number of leaflets, and separateness of leaflets; L. ameghinoi Spegazzini 1897 is prostrate with 3–7 leaflets; the other two are erect shrubs, L. nitida Cavanilles 1800 with 8–16  leaflets, and the tetraploid L. cuneifolia Cavanilles 1800 with fused leaflets (Hunziker et al. 1972, 1977).  Lia et al. (2001) found L. divaricata and L. tridentata to form a monophyletic group, compared to other Larrea species and Zygophyllaceae genera, whereas Laport et al. (2012) indicated L. tridentata monophyletic in comparison to other species in the genus. Larrea divaricata has been postulated to have dispersed from South America to North America 4.2–8.4 million years ago (Lia et al. 2001), or 3.9–4.2 mya (Joy & Crespe 2007), or much more recently, 0.5–1.6 mya (Laport et al. 2012).

Larrea tridentata comprises three more or less geographically separated chromosomal races, a diploid race occurring in the Chihuahuan Desert from southeastern Arizona to western Texas and northern Mexico, a northern hexaploid race in the California Sonoran and Mojave deserts and a tetraploid race centered in southern Arizona Sonoran Desert but overlapping partly with the other two races (Laport et al. 2012).  

Larrea tridentata var. arenaria L. D. Benson 1981, a tetraploid considered endemic to the Algodones Sand Dunes (Felger 2000; Laport et al. 2012), has been distinguished by its relatively erect straight branches and pendulous branchlets (noted on type specimen, and by floral features not specified, while also unsupported by DNA phylogeny (Laport et al. 2012); Kern plants could be further distinguished as var. tridentata (hexaploid).  In Kern County, larger plants seem to occur in Jawbone Canyon than what has been observed elsewhere in the County.

The typical variety of the North American species has been used medicinally by the Cahuilla, Isleta, Paiute, Papago, Shoshoni for treating a variety of ailments including cancer, colds, sores, emetic, stomach cramps, chest infections, rheumatism, cramps, venereal diseases, urinary problems (Moerman; McMinn 1939), and flower buds pickled in vinegar are eaten like “capers” in Mexico (Standley, Contr. U.S. Natl. Herb. 23 pt. 3, 1923). Extensively screened by the NCI prior to 1982 with no antitumor activity reported. Gall midges—fly larvae that live in the twigs and cause a deformed growth of leaves to ball up—are commonly seen on creosote. They comprise a group of related species (as many as 17, Turner et al. 1995), generally referred to Asphondylia auripila (Cecidomyiidae). Another insect that infects creosote, known as “lac scale” secretes a shellac product that was used by the Indians to mend pots and glue arrowheads to their shafts (Ebeling 1986).

Specific References

Hunziker, J. H., R. A. Palacios, L. Poggio, C. A. Naranjo, and T. W. Yang. 1977. Geographic distribution, morphology, hybridization, cytogenetics, and evolution. In Creosote bush: Biology and chemistry of Larrea in New World deserts, US/IBP Synthesis Series 6. Stroudsburg: Dowden, Hutchison and Ross, Inc.

Hunziker, J. H., R. A. Palacios, A. G. De Valesi, and L. Poggio. 1972.  Species disjunctions in Larrea: Evidence from morphology, cytogenetics,  phenolic compounds, and seed albumins. Annals of the Missouri Botanical Garden 59: 224–233.

Joy, J. B. and B. J. Crespi. 2007. Adaptive radiation of gall-inducing insects within a single host-plant species. Evolution 61: 784–795.

Felger, R. S. 2000. Flora of the Gran Desierto and Rio Colorado of northwestern Mexico. Tucson: University of Arizona Press.

Felger, R. S., T. R. Van Devender, B. Broyles, and J. Molusa. 2012. Flora of Tinajas Altas, Arizona—A century of botanical forays and forty thousand years of Neotoma chronicles. J. Bot. Res. Inst. Texas 6:157–257.

Laport, R.G., R.L. Minckley, J. Ramsey. 2012. Phylogeny and cytogeography of the North American Creosote Bush (Larrea tridentata; Zygophyllaceae). Systematic Botany 37: 153-164.

Lia V. V., V. A. Confalonieri, C. I. Comas and J. H. Hunziker.  2001. Molecular phylogeny of Larrea and its allies (Zygophyllaceae): reticulate evolution and the probable time of creosote bush arrival to North America.  Mol. Phylogenet. Evol. 21(2): 309–320. “Nucleotide sequences of Rubisco Large Subunit (rbcL) and the internal transcribed spacers (ITS) of nrDNA were obtained for the five species of Larrea and one species each of Bulnesia (ITS only) and Plectrocarpa (rbcL only). Parsimony analyses were conducted, including sequences from seven genera of Zygophyllaceae reported by other authors-Kallstroemia, Zygophyllum, Augea, Fagonia, Pintoa, Guaiacum, and Porlieria. The main conclusions of the present study are (1) the Argentine endemic Plectrocarpa tetracantha belongs to the subfamily Larreoideae (New World Clade); (2) all three phylogenies obtained from rbcL, ITS, and combined data sets show a close relationship between the tetraploid L. cuneifolia (sect. Bifolium) and the diploid multifoliolate pair L. nitida-L. ameghinoi (sect. Larrea), which could result from a possible intersectional hybrid origin of the tetraploid; (3) L. divaricata (sect. Bifolium) and L. tridentata (sect. Bifolium) form a highly supported monophyletic group, which agrees with previous cytogenetic and molecular evidence; and (4) the rate of nucleotide substitution of rbcL was estimated based on geological and fossil records. Under the molecular clock hypothesis, nucleotide sequence divergence between L. divaricata and L. tridentata suggests a Late Neogene (8.4 to 4.2 mybp) time of arrival of the diploid ancestors of L. tridentata to North American deserts.

Turner RM, Bowers JE, Burgess TL. 1995. Sonoran Desert Plants.  An Ecological Atlas.  The University of Arizona Press, Tucson.