Gutierrezia microcephala

Gutierrezia microcephala is a small, resinous, perennial desert subshrub that is typically {{convert|20|to|60|cm|in}} in height and less than {{convert|100|cm|in}} in diameter.{{cite web|title=Botanical and Ecological Characteristics|url=http://www.fs.fed.us/database/feis/plants/shrub/gutmic/all.html#BOTANICAL%20AND%20ECOLOGICAL%20CHARACTERISTICS|work=Species: Gutierrezia microcephala|publisher=United States Forest Service|accessdate=December 28, 2012}}{{cite web|title=G. microcephala (DC.) A. Gray|url=http://ucjeps.berkeley.edu/cgi-bin/get_JM_treatment.pl?609,1273,1275|work=Treatment from the Jepson Manual|publisher=University of California, Berkeley|accessdate=December 28, 2012}} It is heavily branched, often causing it to be nearly spherical. New shoots and twigs are green to yellow in color, and older parts are brown and woody. The leaves are linear, threadlike, and alternate; {{convert|1|to|4|cm|in}} long and {{convert|0.5|to|2|mm|in}} wide.{{cite web|title=Gutierrezia microcephala (de Candolle) A. Gray|url=http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=250066825|publisher=Flora of North America|accessdate=December 28, 2012}}{{cite web|title=Gutierrezia microcephala (DC.) Gray|url=http://www.wildflower.org/plants/result.php?id_plant=GUMI|work=Lady Bird Johnson Wildflower Center|publisher=University of Texas at Austin|accessdate=December 28, 2012}} Along with the leaves, the stem tissue is photosynthetic, giving the plant a high photosynthetic capacity. G. microcephala typically flowers July to October, but this can vary depending on the amount of precipitation.

File:Gutierrezia microcephala 4.jpg

When flowering, the tips of stem branches are occupied by sessile inflorescences of 5 or 6 flowers. The knobby, waxy yellow flower buds open into golden yellow flower heads, each of which has one or two disc florets between {{convert|2.2|to|3.3|mm|in}} in diameter, and one or two ray florets between {{convert|2.1|to|3.5|mm|in}} in diameter. The mature plants produce many achene, although most seeds fall within a few metres of the parent plant. This is because the plant grows a very small pappus, which makes wind-borne seed distribution very inefficient.

Gutierrezia microcephala, a native North American plant, is found throughout the southwestern United States (from California east as far as Texas and Colorado) and northern Mexico (from Baja California to Tamaulipas, Veracruz, and Zacatecas).{{cite web|title=Distribution and Occurrence|url=http://www.fs.fed.us/database/feis/plants/shrub/gutmic/all.html#DISTRIBUTION%20AND%20OCCURRENCE|work=Species: Gutierrezia microcephala|publisher=United States Forest Service|accessdate=December 28, 2012}}[http://bonap.net/MapGallery/County/Gutierrezia%20microcephala.png Biota of North America Program 2014 county distribution map] It occurs in a variety of ecoregions, such as arid grasslands, chaparral, sand dunes, and oak or oak-pine woodlands. G. microcephala is primarily found in well-drained sandy, gravelly, or rocky soils, and is often found in intermittently dry creeks or on the adjacent slopes. It often predominates on shallow, rocky soil, where grasses are not well established.

Gutierrezia microcephala was used by the Native Americans for various reasons.{{cite web|title=Gutierrezia microcephala|url=http://herb.umd.umich.edu/herb/search.pl?searchstring=Gutierrezia+microcephala|work=Native American Ethnobotany|publisher=University of Michigan|accessdate=December 29, 2012}} The Cahuilla used an infusion of the plant as a gargle or placed the plant in their mouths as a toothache remedy. The Hopi and Tewa both used the plant as a carminative, as prayer stick decorations, and for roasting sweet corn, and the Navajo applied a poultice of the plant to the back and legs of horses for unknown reasons.{{cite journal|last=Hocking|first=George M.|title=Some Plant Materials Used Medicinally and Otherwise by the Navaho Indians in the Chaco Canyon, New Mexico|journal=El Palacio|year=1956|volume=63|url=http://www.chacoarchive.org/docs/000846complete.pdf|accessdate=December 29, 2012|page=151}} The Zuni steeped the flower heads in boiling water and used the tea as a diuretic, tonic, and sweat-inducer, and also used the plant as an indicator of water.{{cite book|last=Dayton|first=William A.|title=Important Western Browse Plants|year=1931|publisher=United States Department of Agriculture|location=Washington, D.C.|url=https://books.google.com/books?id=FqooAAAAYAAJ&pg=PA164|accessdate=February 20, 2013|page=164}}

Gutierrezia microcephala is of little known use to wildlife, and is generally uneaten by livestock except when other forage is unavailable.{{cite web|title=Management Considerations|url=http://www.fs.fed.us/database/feis/plants/shrub/gutmic/all.html#MANAGEMENT%20CONSIDERATIONS|work=Species: Gutierrezia microcephala|publisher=United States Forest Service|accessdate=December 29, 2012}}

Gutierrezia microcephala can be toxic to livestock, especially when grown in sandy soil. Toxicity is due to the presence of saponins, alkaloids, terpenes, and flavonols,{{cite book|last=Smith|first=G. Stanley|title=Noxious Range Weeds|year=1991|publisher=Westview Press|isbn=0-8133-8395-1|author2=Ross, Timothy T. |author3=Flores-Rodriguez, Gonzalo I. |author4=Oetting, Bryan C. |author5= Edrington, Thomas S. |editor=Lynn F. James |editor2=John O. Evans |editor3=Michael H. Ralphs |editor4=R. Dennis Child|page=236|chapter=Toxicology of Snakeweeds, Gutierrezia microcephala and G. sarothrae}} as well as high concentrations of selenium;{{cite web|title=Gutierrezia microcephala|url=http://www.cnr.uidaho.edu/range/toxicplants_horses/Toxic%20Plant%20Database.html|work=Database of Toxic Plants in the United States|publisher=Equines & Toxic Plants|accessdate=December 29, 2012|archive-url=https://web.archive.org/web/20121231230351/http://www.cnr.uidaho.edu/range/toxicplants_horses/Toxic%20Plant%20Database.html|archive-date=December 31, 2012|url-status=dead}} G. microcephala plants have been found to contain selenium levels of 1287 ppm.{{cite journal|last=Beath|first=O. A.|title=Toxic Vegetation Growing on the Salt Wash Sandstone Member of the Morrison Formation|journal=American Journal of Botany|date=November 1943|volume=30|issue=9|doi=10.2307/2437716 |page=701|jstor=2437716}} Toxicity symptoms include abortion and death;{{Cite FTP |title=Poisonous Plant Groups|url=ftp://ftp-fc.sc.egov.usda.gov/ID/technical/technotes/range/range_tn1.pdf|accessdate=December 30, 2012|page=2|server=United States Department of Agriculture Soil Conservation Service|url-status=dead|year=1972}} as little as {{convert|9|kg|lb}} of fresh G. microcephala consumed by cattle in seven days can cause abortions, and in cattle, sheep, and goats consuming ten to twenty percent of their body weight in two weeks can cause death.{{cite web|title=Perennial Broomweed, Broom Snakeweed (Gutierrezia microcephala and G. sarothrae)|url=http://repository.tamu.edu/bitstream/handle/1969.1/86907/pdf_1224.pdf|work=Integrated Toxic Plant Management Handbook|publisher=Texas A&M AgriLife Extension Service|accessdate=December 30, 2012}}

Gutierrezia microcephala is one of the most widespread and damaging rangeland weeds,{{cite journal|last=DeLoach|first=C. Jack|author2=Cuda, James P.|title=Host Specificity of the Argentine Root-Boring Weevil, Heilipodus ventralis (Coleoptera: Curculionidae), a Potential Biocontrol Agent for Snakeweeds (Gutierrezia: Asteraceae) in Western North American Rangelands—U.S. Quarantine Tests|journal=Biological Control|year=1999|volume=15|issue=3|pages=185–209|doi=10.1006/bcon.1998.0684|bibcode=1999BiolC..15..185D |url=http://naldc.nal.usda.gov/download/10642/PDF|archive-url=https://web.archive.org/web/20130408115430/http://naldc.nal.usda.gov/download/10642/PDF|url-status=dead|archive-date=April 8, 2013|accessdate=January 3, 2012|url-access=subscription}} and is an indicator of overgrazed or disturbed rangelands. The herbicides picloram and triclopyr have been found to give satisfactory control, with control lasting at least 5 to 7 years with proper grazing management. Biological control has also been studied, with a combination of an Argentinean root-boring weevil, Heilipodus ventralis, and an Argentinean moth root-borer, Carmenta haematica, found to be an effective method of control.

Fire kills or severely damages G. microcephala, allowing controlled burns to be used in the management of its populations.{{cite web|title=Fire Effects|url=http://www.fs.fed.us/database/feis/plants/shrub/gutmic/all.html#FIRE%20EFFECTS|work=Species: Gutierrezia microcephala|publisher=United States Forest Service|accessdate=December 29, 2012}} Burns must be done carefully, as G. microcephala may recolonize burned sites if moisture conditions and competition is favorable, giving mixed success for prescribed burns. Burns can be limited by insufficient amounts fine fuel; if there is enough fine fuel, burns are generally effective if fuel moisture and relative humidity are low, the air temperature is between {{convert|24|–|32|C|F}}, and there is a gentle breeze.

{{Reflist|colwidth=30em}}

• [http://plants.usda.gov/plant-profile?symbol=GUMI USDA Plants Profile for Gutierrezia microcephala (threadleaf snakeweed)]
• [http://www.calflora.org/cgi-bin/species_query.cgi?where-taxon=Gutierrezia+microcephala Calflora Database: Gutierrezia microcephala (Threadleaf snakeweed)]
• [http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=3142 Jepson Manual eFlora (TJM2) treatment of Gutierrezia microcephala]
• [http://www.swcoloradowildflowers.com/Yellow%20Enlarged%20Photo%20Pages/gutierrezia.htm Southwest Colorado Wildflowers: Gutierrezia]
• [http://www.tropicos.org/Image/100012009 Tropicos.org: photo of herbarium specimen] — collected in Nuevo León (1978).
• [http://calphotos.berkeley.edu/cgi/img_query?query_src=photos_index&where-taxon=Gutierrezia+microcephala UC Photos gallery of Gutierrezia microcephala]
• {{Commons category-inline|Gutierrezia microcephala}}

{{Taxonbar|from=Q5621812}}

microcephala

Category:Flora of Northeastern Mexico

Category:Flora of Northwestern Mexico

Category:Flora of the Southwestern United States

Category:Flora of the South-Central United States

Category:Flora of the California desert regions

Category:Flora of Colorado

Category:Flora of the Great Basin

Category:Flora of the Sonoran Deserts

Category:Plants described in 1836

Category:Taxa named by Asa Gray

Category:Taxa named by Augustin Pyramus de Candolle

Category:Plants used in traditional Native American medicine

Category:Flora without expected TNC conservation status