Musk thistle

Appearance

"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 range in height from 1–1.5 metres tall and have multi-branched stems. Musk thistle has sharply spiny stems and leaves. The stem is cottony/hairy. The plants develop a rosette, with large leaves 30–60 centimetres 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.

Naming

"Carduus nutans" is an invasive species in various regions around the world, including in disturbed and agricultural settings, and in natural habitats. Farmers can spend considerable efforts attempting to minimize the weed in farmlands, including pastures.

Musk thistle was introduced into the eastern North America in the early 19th century, and has been an invasive species there since. It is a declared a noxious weed in many U.S. states, Canadian provinces, South Africa, New Zealand, and Australia. Previous populations in Southern California were eradicated, but it remains in northern California.

Distribution

"Carduus nutans" is a native plant of western North Africa and much of Europe, through Western Asia and Siberia, to Mongolia and Xinjiang, western China. It is an introduced species, and often a noxious weed, in other regions and on other continents.

The plant grows from sea level to an elevation of about 2,500 metres. 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 disturbance events such as landslides and flooding, but does not grow well in excessively wet, dry, or shady conditions.