| Gutierrezia microcephala | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Asterales |
| Family: | Asteraceae |
| Genus: | Gutierrezia |
| Species: | G. microcephala |
| Binomial name | |
| Gutierrezia microcephala | |
| Synonyms[1] | |
Synonymy
| |
Gutierrezia microcephala is a species of flowering plant in the familyAsteraceae known by the common namessticky snakeweed,threadleaf snakeweed,threadleaf broomweed, andsmallhead snakeweed. It is asubshrub native to the southwestern United States and northern Mexico, and can be found in aridgrassland and desert sanddune habitats. It can be toxic to livestock in large quantities, due to the presence ofsaponins and high concentrations ofselenium.
Gutierrezia microcephala is a small,resinous,perennial desert subshrub that is typically 20 to 60 centimetres (7.9 to 23.6 in) in height and less than 100 centimetres (39 in) in diameter.[2][3] It is heavily branched, often causing it to be nearly spherical.[3] New shoots and twigs are green to yellow in color, and older parts are brown and woody.[3] The leaves are linear, threadlike, and alternate; 1 to 4 centimetres (0.39 to 1.57 in) long and 0.5 to 2 millimetres (0.020 to 0.079 in) wide.[3][4][5] Along with the leaves, the stem tissue isphotosynthetic, giving the plant a highphotosynthetic capacity.[2]G. microcephala typically flowers July to October,[3] but this can vary depending on the amount of precipitation.[2]
When flowering, the tips of stem branches are occupied bysessileinflorescences of 5 or 6 flowers. The knobby, waxy yellow flowerbuds open into golden yellowflower heads, each of which has one or two disc florets between 2.2 to 3.3 millimetres (0.087 to 0.130 in) in diameter, and one or two ray florets between 2.1 to 3.5 millimetres (0.083 to 0.138 in) in diameter.[3] The mature plants produce manyachene, although most seeds fall within a few metres of the parent plant.[2] This is because the plant grows a very smallpappus, which makes wind-borne seed distribution very inefficient.[2]
Gutierrezia microcephala, a native North American plant, is found throughout the southwestern United States (fromCalifornia east as far asTexas andColorado) and northern Mexico (fromBaja California toTamaulipas,Veracruz, andZacatecas).[1][6][7] It occurs in a variety ofecoregions, such as arid grasslands,chaparral, sand dunes, and oak or oak-pinewoodlands.[3][4][6]G. microcephala is primarily found in well-drained sandy, gravelly, or rocky soils, and is often found inintermittently dry creeks or on the adjacent slopes.[2] It often predominates on shallow, rocky soil, where grasses are not well established.[2]
Gutierrezia microcephala was used by theNative Americans for various reasons.[8] TheCahuilla used an infusion of the plant as a gargle or placed the plant in their mouths as a toothache remedy. TheHopi andTewa both used the plant as acarminative, asprayer stick decorations, and for roasting sweet corn, and theNavajo applied a poultice of the plant to the back and legs of horses for unknown reasons.[9] TheZuni steeped the flower heads in boiling water and used the tea as adiuretic,tonic, and sweat-inducer, and also used the plant as an indicator of water.[10]
Gutierrezia microcephala is of little known use to wildlife, and is generally uneaten by livestock except when other forage is unavailable.[10][11]
Gutierrezia microcephala can be toxic to livestock, especially when grown in sandy soil.[11] Toxicity is due to the presence of saponins,alkaloids,terpenes, andflavonols,[12] as well as high concentrations of selenium;[13]G. microcephala plants have been found to contain selenium levels of 1287 ppm.[14] Toxicity symptoms include abortion and death;[11][15] as little as 9 kilograms (20 lb) of freshG. 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.[16]
Gutierrezia microcephala is one of the most widespread and damagingrangeland weeds,[17] and is an indicator ofovergrazed or disturbed rangelands.[11] The herbicidespicloram andtriclopyr have been found to give satisfactory control, with control lasting at least 5 to 7 years with proper grazing management.[11] 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.[17]
Fire kills or severely damagesG. microcephala, allowing controlled burns to be used in the management of its populations.[18] Burns must be done carefully, asG. microcephala may recolonize burned sites if moisture conditions and competition is favorable, giving mixed success for prescribed burns.[18] Burns can be limited by insufficient amounts fine fuel; if there is enough fine fuel, burns are generally effective if fuel moisture andrelative humidity are low, the air temperature is between 24–32 °C (75–90 °F), and there is a gentle breeze.[18]
Media related toGutierrezia microcephala at Wikimedia Commons
