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Crepis tectorum

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Crepis tectorum, the narrowleaf hawksbeard<ref>Template:PLANTS</ref> or narrow-leaved hawk's-beard,<ref name=BSBI07>Template:Cite web</ref> is an annual or winter annual plant that grows to Template:Convert high.<ref name="Nadja">Template:Cite journal</ref> It is an invasive species and during maturity it has one main stem, which is branched, hairless, and leafy. The leaves are arranged in an alternate manner and are less than Template:Convert wide. The Greek word krepis means sandal or slipper which resembles the shape of the seed.<ref>Template:Cite web</ref> Narrowleaf hawksbeard originated in Siberia and was introduced to Canada around 1890.<ref name="Nadja"/>

Distribution

Crepis tectorum is native to most of Europe,<ref>Altervista Flora Italiana, Radicchiella dei tetti, Dach-Pippau, takfibbla, Crepis tectorum L. includes photos and European distribution map</ref> as well as northern and central Asia (Russia, Kazakhstan, Mongolia, and parts of China (Inner Mongolia, Heilongjiang, Xinjiang)).<ref>Flora of China, 屋根草 wu gen cao, Crepis tectorum Linnaeus, Sp. Pl. 2: 807. 1753. </ref>

The species is now naturalized in much of Canada, Greenland, and northern parts of the United States including Alaska.<ref>Biota of North America Program 2014 county distribution map</ref> Narrowleaf hawksbeard is now commonly found in the parkland zone of Alberta, Saskatchewan and Manitoba.<ref name="Nadja"/> Crepis tectorum is found in waste areas, conventional tillage, reduced tillage, forage and hay fields, and roadsides.<ref>Template:Cite book</ref><ref name="Bubar">Template:Cite web</ref>

Identification

Crepis tectorum is identified by its long, erect stem and yellow, dandelion-like flowers.<ref name="Nadja"/> The leaves are pointed and lobed with a length of Template:Convert and width up to Template:Convert.<ref name="Nadja"/> The flower heads look like they contain single flowers, but in fact they contain many ray florets.<ref name="Nadja"/>

Seedling

Crepis tectorum may look similar to a dandelion at this stage but will have teeth that point downward on the underside leaf margin.<ref name="Bubar"/> The cotyledons are oval and the first true leaves are more elongated with petioles.

Juvenile

The juvenile stage of the narrowleaf hawksbeard is distinguishable by its rosette of leaves.<ref name="Bubar"/> The stem may contain a milky-white latex.<ref name="Bubar"/>

Mature

A mature Crepis tectorum plant will have dandelion-like flowers, with many flower heads on each stem.<ref name="Bubar"/> When the plant had gone to seed it will have a white, fluffy head where the flower used to be.<ref name="Bubar"/> The seeds are dark purple/brown achenes dispersed by the wind using hairs called the pappus.<ref name="Nadja"/>

Habitat and ecology

Pollination

Crepis tectorum is an annual weed that grows in cultivated fields and roadsides. It is very invasive so it can take over a field and lead to serious ecological impacts for the surrounding. Crepis tectorum is able to grow in calcareous soil as well as soil that does not contain lime.<ref name="Nadja"/> However, it grows best in nutrient rich soils containing clays and loams.<ref name="Nadja"/> It also thrives in dry, coarse soil. It grows with other species in the wild however, it becomes infectious if not controlled by humans. It can easily be removed by hand, although it can be controlled better by chemical means. The presence of the Narrowleaf hawksbeard is damaging to the soil and other species of plants nearby as it generally takes over the area. The temperature range for germination is Template:Convert, with an optimum depth of Template:Convert.<ref>Template:Cite web</ref> Narrow-leaved hawksbeard grows on both calcareous and lime-deficient soils.

Morphology

Illustration of C. tectorum

Individuals of this species are usually approximately Template:Convert tall, single-stemmed, yellow petals on flowers, and produce 30–70 yellow ray florets.

Flowers and fruit

Inflorescences of Crepis tectorum are approximately ½-¾ inches wide and are hermaphrodite, having both male and female organs. It produces small flowers from June until September. The fruit is cylindrical shaped and dark brown. The fruit of Crepis tectorum is dry and is called an achene.<ref name="Nadja"/>

Methods of control

Narrowleaf hawksbeard responds best to a fall application of 2,4-DB herbicide.<ref name="Nadja" /> Non-chemical methods of control include spring or fall tillage to control winter annuals and the correct use of agronomic practices such as fertilization for the control of annuals.<ref name="Nadja"/> Biological control can be achieved by insects, non-domestic animals, microorganisms, and viruses.<ref name="Nadja"/> However, the use of biological control can be risky and should always be approached with caution.

References

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