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Species
Centaurea solstitialis L.
IUCN
NCBI
EOL Text
Annuals, 10–100 cm. Stems simple or often branched from base, forming rounded bushy plants, gray-tomentose. Leaves gray-tomentose and scabrous to short-bristly; basal and proximal cauline petiolate or tapered to base, usually absent at anthesis, blades 5–15 cm, margins pinnately lobed or dissected; cauline long-decurrent, blades linear to oblong, 1–10 cm, entire. Heads disciform, borne singly or in open leafy arrays, long-pedunculate. Involucres ovoid, 13–17 mm, loosely cobwebby-tomentose or becoming glabrous. Principal phyllaries: bodies pale green, ovate, appendages stramineous to brown, each with palmately radiating cluster of spines, and stout central spine 10–25 mm. Inner phyllaries: appendages scarious, obtuse or abruptly spine tipped. Florets many. corollas yellow, all ± equal, 13–20 mm; sterile florets slender, inconspicuous. Cypselae dimorphic, 2–3 mm, glabrous, outer dark brown, without pappi, inner white or light brown, mottled; pappi of many white, unequal bristles 2–4 mm, fine. 2n = 16.
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Rights holder/Author | eFloras.org Copyright © Missouri Botanical Garden |
Source | http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242416255 |
Centaurea solstitialis is a serious weed pest, especially in the western United States, where it has invaded millions of acres of rangelands, and it is listed as a noxious weed in eleven western states and two Canadian provinces. It is a strong competitor in infested areas, often forming dense colonies. It is very difficult to control or eradicate once it becomes established. In addition, yellow star-thistle is poisonous to horses; when ingested over a prolonged period it causes a neurological disorder called equine nigropallidal encephalomalacia, or "chewing disease." Although its bitter taste and spiny heads usually deter grazing animals, horses sometimes will seek it out. Yellow star-thistle tends to spread in rangelands when more palatable plants are consumed.
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | eFloras.org Copyright © Missouri Botanical Garden |
Source | http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242416255 |
Yellow starthistle is an annual herbaceous plant. Plants are gray-green to blue-green, grow from 6 in. to 5 ft. (15 cm to 15 dm) in height, and have deep taproots. Flowers are bright yellow with sharp spines surrounding the base, giving the plant a particularly menacing appearance and a painful response if touched. Stems and leaves are covered with cottony wool. Basal leaves are 2 to 3 in. (6 – 7 cm.) long and deeply lobed . Upper leaves are short (0.5 to 1.0 in.; 1 to 2.5 cm) and narrow, with few lobes.
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More info for the term: therophyte
RAUNKIAER [109] LIFE FORM:
Therophyte
yellow starthistle
yellow star-thistle
yellow star thistle
St. Barnaby's thistle
More info for the terms: competition, cover, density, natural
Yellow starthistle is most often found on roadsides and abandoned fields and pastures, waste places, recreational areas and disturbed grassland or woodland [32,49,55,158]. It is a problem primarily in moderately warm, exposed areas on relatively dry, fertile soils [32].
Yellow starthistle is best adapted to open grasslands with average annual precipitation between 10 and 60 inches (250-1500 mm). It is generally associated with deep, well-drained soils. Although populations can occur at elevations from sea level to as high as 8,000 feet (2,400 m), most large infestations are found below 5,000 feet (1,500 m) [30,82]. The optimum environmental conditions for yellow starthistle appear to be in northern California's mediterranean-type climate (cool, wet winter and hot, dry summer), which enable yellow starthistle to grow during winter, bolt in spring, and escape summer drought [81,139]. Yellow starthistle is uncommon in deserts and moist coastal sites [32].
Yellow starthistle is capable of establishment and at least short-term persistence in any of the major plant communities in Washington below subalpine, but demonstrates its maximum potential in the bluebunch wheatgrass (Pseudoroegneria spicata)-Idaho fescue (Festuca idahoensis) zone of the steppe region of the Columbia Basin Province. In this community, on the southern slopes of the foothills of the Blue Mountains, it appears to reach its northern limits. Occasional small populations are found farther north, but the farther north the more they are restricted to steep south-facing slopes [121,145]. Here it is most competitive on deep silt loam soils on south slopes of the higher natural grassland types. In other areas, compensating factors for moisture or heat were found, or yellow starthistle was not competitive, producing only a few heads on a dwarfed plant [119]. Although yellow starthistle more readily invades and dominates south slopes and disturbed sites in southwestern Oregon, it is not restricted to them. In the absence of competitive perennial vegetation, yellow starthistle often forms dense stands on valley floors and invades openings in the conifer transition zone above oak woodlands [118]. In north-central Idaho, yellow starthistle infestations thrive in disturbed areas with high sunlight exposure and well-drained soils that receive 10 to 30 inches (254-762 mm) of precipitation per year [20].
On annual rangelands where yellow starthistle occurs with cheatgrass, population dominance oscillates between yellow starthistle and cheatgrass [130]. Yellow starthistle invades and dominates annual grasslands by using the deep soil moisture that remains after shallow-rooted annual grasses die in early summer [118]. Areas with deep soil and years with moderate to heavy spring rainfall give yellow starthistle the greatest advantage [74]. In dry spring conditions (and shallow soils), early maturing annual grasses have the advantage [130], although yellow starthistle can also survive at extremely low soil water potential (<-6.0 MPa) as compared to annual grasses (>-2.1 MPa) [35]. Growth rates of cheatgrass and yellow starthistle appear to depend primarily on plant density, soil depth, and available soil moisture [132]. Sheley and Larson [130] suggest that intraspecific competition is more important for both yellow starthistle and cheatgrass than is interspecific competition, citing evidence of resource partitioning via root depth, allowing for greater niche occupation on a site.
Yellow starthistle seedlings are more likely to dominate in deep silt loam and loam soils with few coarse fragments [74,145], but they can also establish on shallow, rocky soils [79,82]. In deep soils, yellow starthistle can reduce soil moisture reserves to depths greater than 6 feet (~2 m), and in 3-foot-deep (~1 m) foothill soils it can extract soil moisture from fissures in bedrock [35,45]. A Washington study suggested a relationship between yellow starthistle cover and soil depth or total moisture-holding capacity of the soil on south-facing aspects. Here, yellow starthistle may be dependent on the ability of the soil to retain sufficient moisture for the maturation of the plant during the summer drought period [116,117,145]. Studies in southeastern Washington natural grasslands indicated that the dual requirements of soil moisture for reproduction during the summer drought period, and light for winter growth may be critical limiting factors for yellow starthistle [116].
At its northern limit in Washington state (48° 45' north latitude), yellow starthistle is restricted to south-facing slopes [116]. Yellow starthistle's conspicuous absence on north aspects in this area appears to be related to heat and light [116,117]. This may explain why it has not persisted in British Columbia [115], and why it has gradually disappeared in northern areas of Romania (46° 47' north latitude) (Prodan (1930) as cited by [115,116]). A critical factor at the northern limits of yellow starthistle appears to be radiation during the winter [116]. Yellow starthistle needs sunlight at the soil surface from fall through spring to grow roots long enough to tap water stored deep in the soil during summer drought [118]. Yellow starthistle seedlings can survive extended frost periods, but mature plants rarely survive the winter in cold climates. Cold tolerance appears to be lost during the transition from vegetative to reproductive phases [30].
When yellow starthistle seed from 34 distinct stands in California, Idaho, Oregon, and Washington was grown in a uniform nursery at Pullman, Washington, there was wide biotypic variation for the following variables: rosette area, decurrent leaf width, plant height, stature, number of branches, shape and form, growth stage on four dates, number of buds produced on 2 dates, flowering rate, date of first flower and first seed, average number of flowers, and seed production rate. None of the variables correlated with precipitation, elevation, or latitude of the population source [113].
More info for the term: forb
Forb
Yellow starthistle was probably introduced into the United States through contaminated alfalfa in the mid-1800’s.
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This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):
More info for the terms: cover, shrub
SRM (RANGELAND) COVER TYPES [136]:
101 Bluebunch wheatgrass
102 Idaho fescue
103 Green fescue
104 Antelope bitterbrush-bluebunch wheatgrass
105 Antelope bitterbrush-Idaho fescue
107 Western juniper/big sagebrush/bluebunch wheatgrass
109 Ponderosa pine shrubland
110 Ponderosa pine-grassland
201 Blue oak woodland
202 Coast live oak woodland
203 Riparian woodland
204 North coastal shrub
205 Coastal sage shrub
206 Chamise chaparral
207 Scrub oak mixed chaparral
208 Ceanothus mixed chaparral
209 Montane shrubland
210 Bitterbrush
214 Coastal prairie
215 Valley grassland
235 Cottonwood-willow
311 Rough fescue-bluebunch wheatgrass
312 Rough fescue-Idaho fescue
314 Big sagebrush-bluebunch wheatgrass
315 Big sagebrush-Idaho fescue
316 Big sagebrush-rough fescue
317 Bitterbrush-bluebunch wheatgrass
318 Bitterbrush-Idaho fescue
319 Bitterbrush-rough fescue
322 Curlleaf mountain-mahogany-bluebunch wheatgrass
401 Basin big sagebrush
402 Mountain big sagebrush
403 Wyoming big sagebrush
404 Threetip sagebrush
405 Black sagebrush
406 Low sagebrush
407 Stiff sagebrush
408 Other sagebrush types
409 Tall forb
412 Juniper-pinyon woodland
Consumption of yellow starthistle plants by fire is not necessary to kill the plants, although sufficient heat is required to scorch the foliage, stem-girdle, and kill them [53].