Crepis tectorum

Crepis tectorum is native to most of Europe,[6] as well as northern and central Asia (Russia, Kazakhstan, Mongolia, and parts of China (Inner Mongolia, Heilongjiang, Xinjiang)).[7]

The species is now naturalized in much of Canada, Greenland, and northern parts of the United States including Alaska.[8] Narrowleaf hawksbeard is now commonly found in the parkland zone of Alberta, Saskatchewan and Manitoba.[4] Crepis tectorum is found in waste areas, conventional tillage, reduced tillage, forage and hay fields, and roadsides.[9][10]

Crepis tectorum is identified by its long, erect stem and yellow, dandelion-like flowers.[4] The leaves are pointed and lobed with a length of 10–15 centimetres (3.9–5.9 in) and width up to 4 cm (1.6 in).[4] The flower heads look like they contain single flowers, but in fact they contain many ray florets.[4]

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.[4] However, it grows best in nutrient rich soils containing clays and loams.[4] 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 2–4 °C (36–39 °F), with an optimum depth of 3–4 cm (1.2–1.6 in).[11]

Illustration of C. tectorum

Individuals of this species are usually approximately 3 feet (0.91 m) tall, single-stemmed, yellow petals on flowers, and produce 30–70 yellow ray florets.

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.[4]

Narrowleaf hawksbeard responds best to a fall application of 2,4-DB herbicide.[4] 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.[4] Biological control can be achieved by insects, non-domestic animals, microorganisms, and viruses.[4] However, the use of biological control can be risky and should always be approached with caution.