Larrea tridentata, called creosote bush and greasewood as a plant,[2]chaparral as a medicinal herb,[3] and gobernadora (Spanish for "governess") in Mexico, due to its ability to secure more water by inhibiting the growth of nearby plants.[citation needed] In Sonora, it is more commonly called hediondilla;[4] Spanish hediondo = "smelly".
Stages of creosote flower development, from bud (left) to fruit and seeds (right)
Larrea tridentata is an evergreenshrub growing to 1 to 3 m (3 to 10 ft) tall, rarely 4 m (13 ft). The light gray stems of the plant bear resinous, dark green leaves with two oppositelanceolate leaflets joined at the base, with a deciduous awn between them, each leaflet 7 to 18 mm (1⁄4 to 11⁄16 in) long and 4 to 8.5 mm (5⁄32 to 11⁄32 in) broad. The flowers are up to 25 mm (1 in) in diameter, with five yellow petals. The fruit is a brown-burgundy spherical, fuzzy capsule, which separates into five individual carpels each containing one seed.[7]Galls may form by the activity of the creosote gall midge. The whole plant exhibits a characteristic odor of creosote, from which the common name derives.[8] In the regions where it grows, its smell is often associated with the "smell of rain".[9]
King Clone, the 11,700-year-old creosote bush ring in the Mojave Desert
As the creosote bush grows older, its oldest branches eventually die and its crown splits into separate crowns. This normally happens when the plant is 30 to 90 years old. Eventually, the old crown dies and the new ones become a clonal colony from the previous plant, composed of many separate stems all from the same seed. The cloned individuals sometimes form a "ring" around the original plant, which may no longer be visible.[13]
The "King Clone" creosote ring is one of the oldest living organisms on Earth. It has been alive an estimated 11,700 years, in the central Mojave Desert near present-day Lucerne Valley, California. This single clonal colony plant of L. tridentata reaches up to 20 m (67 ft) in diameter, with an average diameter of 14 m (45 ft).[14][15][16]
King Clone was identified and its age estimated by Frank Vasek, a professor at the University of California, Riverside. Measurements of the plant, as well as radiocarbon dating of wood fragments, were used to determine the plant's mean annual growth rate outward from the center of the ring. By measuring the diameter of the ring, its total age could be estimated.[16][17] It is within the Creosote Rings Preserve of the Lucerne Valley and Johnson Valley.[16]
Creosote bush is most common on the well-drained soils of alluvial fans and flats. In parts of its range, it may cover large areas in practically pure stands, though it usually occurs in association with Ambrosia dumosa (burro bush or bur-sage).[18] Chemicals found in creosote bush roots have been shown to inhibit the growth of burro bush roots,[19] but as of 2013, much of their relationship remains unexplained.
Creosote bush stands tend to display an evenly spaced distribution of plants.[20] Originally, [citation needed] it was assumed that the plant produced a water-soluble inhibitor that prevented the growth of other bushes near mature, healthy bushes. Now, however, it has been shown [citation needed] that the root systems of mature creosote plants are simply so efficient at absorbing water that fallen seeds nearby cannot accumulate enough water to germinate, effectively creating dead zones around every plant.[21]
Desert adaptation
A young L. tridentata plant
Owing to the harshness of the germination environment above mature root systems, young creosote bushes are much more susceptible to drought stress than established plants. Germination is quite active during wet periods, but most of the young plants die very quickly unless water conditions are optimal. Ground heat compounds the young plants' susceptibility to water stress, and ground temperatures can reach upwards of 70 °C (160 °F). To become established, the young plant apparently must experience three to five years of abnormally cool and moist weather during and after germination. From this, it can be inferred that all the plants inside a stand are of equal age.
Mature plants, however, can tolerate extreme drought stress. In terms of negative water potential, creosote bushes can operate fully at −50 bars of water potential and have been found living down to −120 bars, although the practical average floor is around −70 bars, where the plant's need for cellular respiration generally exceeds the level that the water-requiring process of photosynthesis can provide. Cell division can occur during these times of water stress, and new cells commonly quickly absorb water after rainfall. This rapid uptake causes branches to grow several centimeters at the end of a wet season.
Water loss is reduced by the resinous waxy coating of the leaves, and by their small size, which prevents them from heating above air temperature (which would increase the vapor pressure deficit between the leaf and the air, thus increasing water loss). Plants drop some leaves heading into summer, but if all leaves are lost, the plant will not recover. Accumulation of fallen leaves, as well as other detritus caught from the passing wind, creates an ecological community specific to the creosote bush canopy, including beetles, millipedes, pocket mice, and kangaroo rats.
In other uses, the reddish-colored lac that exudes from the plant was used by the Tohono O'odham, after boiling, to make a mending glue on broken pottery.[26]
Herbal supplements and toxicity
Larrea tridentata is often referred to as chaparral when used as a herbal remedy and supplement; however, it does not grow in the synonymous plant communitychaparral.[27] The United States Food and Drug Administration has issued warnings about the health hazards of ingesting chaparral or using it as an internal medicine, and discourages its use.[28] In 2005, Health Canada issued a warning to consumers to avoid using the leaves of Larrea species because of the risk of damage to the liver and kidneys.[29]
Cancer Research UK states: "We don't recommend that you take chaparral to treat or prevent any type of cancer."[30]
^Peter Bigfoot (2011). "Chaparral". Peter Bigfoot's Useful Wild Western Plants. Archived from the original on 15 July 2014. Retrieved 17 February 2013.
^Moore, M. (1989). Medicinal Plants of the Desert and Canyon West. Santa Fe, NM: Museum of New Mexico Press. pp. 27–32. ISBN978-0-8901-3181-7.
^ abLemm, Jeffrey.(2006) Field Guide to Amphibians and Reptiles of the San Diego Region (California Natural History Guides). University of California Press.
^"Creosote Bush". US National Park Service. Retrieved 30 December 2011.
^Vasek, F. C. (February 1980). "Creosote Bush: Long-Lived Clones in the Mojave Desert". American Journal of Botany. 67 (2): 246–255. doi:10.2307/2442649. JSTOR2442649.
^Bowers, Janice; Wignall, Brian (1993). Shrubs and Trees of the Southwest Deserts. Arizona: Western National Parks Association. p. 104.
^Arteaga S; Andrade-Cetto A; Cárdenas R (April 2005). "Larrea tridentata (Creosote bush), an abundant plant of Mexican and US-American deserts and its metabolite nordihydroguaiaretic acid". J Ethnopharmacol. 98 (3): 231–9. doi:10.1016/j.jep.2005.02.002. PMID15814253.
^Fontana, Bernard L.; Robinson, William J.; Cormack, Charles W.; Leavitt, Earnest E. (1962). Papago Indian Pottery. Seattle, Washington: University of Washington Press, on behalf of the American Ethnological Society. p. 81. OCLC869680.
^Nabhan, G. P. (1993). Gathering the Desert. University of Arizona Press. p. 16. ISBN978-0-8165-1014-6. ...health food stores have been marketing Larrea as a cure-all that they whimsically called "chaparral tea" – the plant never grows above the desert in true chaparral vegetation.
^Tilford, G. L. (1997). Edible and Medicinal Plants of the West. Missoula, MT: Mountain Press Publishing. ISBN978-0-87842-359-0.
