''Carduus nutans'', with the common names musk thistle, nodding thistle, and nodding plumeless thistle, is a

biennial plant A biennial plant is a flowering plant that, generally in a temperate climate, takes two years to complete its biological life cycle. Life cycle In its first year, the biennal plant undergoes primary growth, during which its vegetative structures ...

in the daisy and sunflower family Asteraceae. It is native to regions of Eurasia.

Description

''Carduus nutans'' is usually a biennial, requiring 2 years to complete a reproductive cycle. However, it may germinate and flower in a single year in warmer climates. Seedlings may emerge at any time from spring to late summer and develop a rosette. Plants overwinter in the rosette stage, sending up a multi-branched flowering stem in mid-spring of their second year. Mature plants reach in height with multi-branched stems. It has sharply spiny stems and leaves. The stem is cottony/hairy. The plants develop a rosette, with large leaves up to about long. The leaves are dark green, coarsely bipinnately lobed, with a smooth, waxy surface and sharp yellow-brown to whitish spines at the tips of the lobes. They are more or less hairy on top, and wooly on the veins below.

Flowers

The plant bears showy red-purple flowers. The large globose

flower heads A pseudanthium (Greek for "false flower"; ) is an inflorescence that resembles a flower. The word is sometimes used for other structures that are neither a true flower nor a true inflorescence. Examples of pseudanthia include flower heads, compos ...

, containing hundreds of tiny individual flowers, are (rarely to 7 cm) in diameter and occur at the tips of stems. The flower heads commonly droop to a 90° to 120° angle from the stem when mature, hence its alternate name of "nodding thistle". Each plant may produce thousands of straw-colored seeds adorned with plume-like bristles. They are 4 to 6 cm across, with purple-red

bract In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...

s. The number of flowerheads per plant is site-dependent and ranges from about 20–50 on good sites and 1–20 on poor sites. Flowering occurs from June to October, and seed dissemination occurs approximately one month after the flowers form. A single flower head may produce 1,200 seeds and a single plant up to 120,000 seeds, which are wind dispersed. The seeds may remain viable in the soil for over ten years, making it a difficult plant to control.

Distribution and habitat

''C. nutans'' is a native plant of Eurasia. It is an introduced species, and often a

noxious weed A noxious weed, harmful weed or injurious weed is a weed that has been designated by an agricultural or other governing authority as a plant that is injurious to agricultural or horticultural crops, natural habitats or ecosystems, or humans or liv ...

, in other regions and on other continents. It is abundant in region of the North American Rocky Mountains. The plant grows from sea level to an elevation of about . It is found in neutral to acidic soils. It typically grows in meadows and grasslands, in heavily grazed land in areas such as pastures, and on open disturbed soil such as roadsides and building sites. It spreads rapidly in areas subjected to frequent natural disturbances such as landslides and flooding, but does not grow well in excessively wet, dry, or shady conditions.

As an invasive species

''C. nutans'' is an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

in various regions around the world, including in disturbed and agricultural settings, and in natural habitats. Musk thistle was introduced into eastern

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

in the early 19th century, and has been an invasive species there since. It is declared a

in many U.S. states,

Canadian province Within the geographical areas of Canada, the ten provinces and three territories are sub-national administrative divisions under the jurisdiction of the Canadian Constitution. In the 1867 Canadian Confederation, three provinces of British North ...

s, South Africa, New Zealand, and

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. Previous populations in Southern California were eradicated, but it remains in northern California.Cal IPC—California Invasive Plants Council: ''Carduus nutans'' (musk thistle)
/ref>

References

External links

Jepson Manual Treatment: Carduus nutansU.S. National Invasive Species Information Center: Species Profile — Musk Thistle (''Carduus nutans'')
— ''Lists general information and resources. From the United States National Agricultural Library''.
Biological Control of the Musk Thistle in Kansas
Biological Control of Musk Thistle in Kansas
''Carduus nutans'' — U.C. Photo gallery
{{Taxonbar, from=Q1431280 nutans Flora of North Africa Flora of Western Asia Flora of Europe Flora of Afghanistan Flora of Algeria Flora of Estonia Flora of Germany Flora of Greece Flora of Iran Flora of Ireland Flora of Italy Flora of Kazakhstan Flora of Mongolia Flora of Morocco Flora of Russia Flora of Siberia Flora of Spain Flora of Switzerland Flora of Tunisia Flora of Ukraine Flora of the United Kingdom Flora of Xinjiang Plants described in 1753 Taxa named by Carl Linnaeus