Carduus nutans Linnaeus

Remark The words or terms in red (actually dark orange) in the text are defined in a glossary.


jul_07_11n.gthmb can't be loaded. Carduus nutans is an erect biennial or annual plant with spiny leaves and stems that may reach 6 feet in height. In North America, it is an introduced species native (as all the species of the Carduus genus) to Eurasia and northern Africa. It is primarily a weed of pastures, hayfields, roadsides, and noncrop areas that can be found throughout Canada and the United States. The plant was introduced in to the eastern United States in the early 1800s. During the first year of growth as a biennial, the plant produces a basal rosette of leaves. During the second year of growth, the rosettes elongate and flowering stems are produced. Carduus nutans as a chromosome number (2n) of 16. The species belongs to the Asteraceae family.

Name

In Latin, cardus or carduus is the generic name for the thistle as cited by the Roman poet Publius Vergilius Maro (Vergil), 70 BC-19 BC, in De Georgica (The Georgics), a poem on the subject of agriculture. Thistles include many genera and many species of the subfamily Cynareae of the Asteraceae family, Cirsium, Silybum and Carduus. It is also the name of the artichoke, (Cynara cardunculus var. scolymus), cited by Plinius Secundus (Pliny the Elder), 23 AD - 70 AD, in Naturalis Historia (Natural History). Although the artichoke does not belong to the Carduus genus there is some similarity between the artichoke and thistles.

In Latin, nutans is the present participle of a verb that means to make a sign by moving the head and can be interpreted as nodding, the epithet referring then to the flower heads, that are usually nodding, at least when in fruits.

Common names

Some of the vernacular names of Carduus nutans are: Musk Thistle, Nodding Plumeless Thistle and Nodding Thistle. Some of the French vernacular names are Chardon penché and Chardon aux ânes.

Synonyms

Carduus nutans has also been known as:

Identification

Carduus nutans is identified by its spiny erect branches, its spiny deeply lobed leaves, and its relatively large pink to violet or purple flowers. It is somewhat similar to Cirsium vulgare, however the later has many hairs on the upper surface of the leaf blades unlike Carduus nutans which mostly lacks hairs. Carduus nutans is also somewhat similar to Cirsium arvense, however the later has rhizomes rather than a taproot and rarely takes on a rosette growth habit unlike either Carduus nutans or Cirsium vulgare.

In fact, at one time botanists considered the species of Cirsium to be Carduus taxa. The significant difference between these two genera is the nature of the pappus. The Cirsium species can be distinguished from the Carduus species by the plumose pappus of their seeds. draw.jpg can't be loaded. The members of the Carduus genus are know as plumeless thistles because of their simple, not plumose, pappus. In the genus Carduus the pappus is composed of capillary bristles that are naked, single, and silky; whereas in the genus Cirsium the pappus is composed of featherlike bristles. The pappus should always be examined to determine the genus of an unidentified thistle.

It is not to difficult to differentiate the three species of Carduus found in Québec. Carduus nutans plants have larger involucres, from 20 mm up to 70 mm, than the other two species, Carduus acanthoides and Carduus crispus; their involucre is up to or less than 20 mm.

Description

As a biennial, Carduus nutans initially forms a prostrate rosette of leaves that can grow up to 10 inches long and 4 inches wide, the rosettes being up to 2 feet or more in diameter. The second year the plant put forth 1 to 7 branched stems that grow 2 to 6 feet.

Roots

Stems

Leaves

Flower heads

Fruits

Habitat

Carduus nutans grows from sea level to an elevation of about 2,500 m in neutral to acidic soils. It typically grows on open disturbed soil or heavily grazed land in areas such as meadows, arable land, roadsides, building sites, fencerows, waste places, and similar. 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.

Distribution

map_us.jpg can't be loaded. In North America, Carduus nutans is found in all the USA states but for New England and Florida as shown on the map. It is also found in all Canadian Provinces, but not in the Canadian Territories. It is also found in western and central Europe, extending northwards to Scotland, southward to Sicilia, eastward to central Yugoslavia and Ukraine; it is also found in western Siberia, Asia Minor, and in North Africa, all regions where the plant is native. Besides North America, the plant has also been introduced in South America, Australia, and New Zealand.

Notes

Carduus nutans is one of the most serious weeds in North America. It is unpalatable to wildlife and livestock and often forms dense, impenetrable stands in pastures and rangelands. It readily colonizes disturbed sites in many different habitats. A single large terminal head can produce as many as 1200 cypselae. An introduced biological control agent, the musk thistle weevil (Rhinocyllus conicus) feeds on the seeds and can limit the spread of this plant. but will not eliminate it.

Carduus nutans is not palatable to livestock because of its long sharp spines, but it does provide a source of nectar for high quality honey.

Gallery

The photos of the gallery were taken either with one of the following: The title in the window shows the date when the picture was taken, i.e. jan_30_06... would mean that the photo was taken on the 30th of January, the 06 is for the 6th picture taken that day.

The month, day and picture number might be followed by a letter:

Click on the thumbnails to get larger view. The original photos are usually in TIFF format, the photos shown are generally in JPEG format, usually of dimensions one half (surface one quarter) for loading time reduction.

Plants, stems

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Flower heads

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