Carduus nutans Linnaeus
The words or terms in red
(actually dark orange) in the text are defined in a
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
Carduus nutans as a
chromosome number (2n) of 16.
The species belongs to the
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.
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.
Carduus nutans has also been known as:
- Carduus macrocephalus Desfontaines
- Carduus macrolepis Petermann
- Carduus nutans subsp. leiophyllus (Petrovic) Stojanov
- Carduus nutans subsp. macrocephalus (Desfontaines) Nyman
- Carduus nutans var. macrocephalus (Desfontaines) B. Boivin
- Carduus nutans subsp. macrolepis (Petermann) Kazmi
- Carduus nutans var. vestitus (Hallier) B. Boivin
- Carduus thoermeri Weinmann
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
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.
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.
- Large, thick taproot.
- Hollow near the soil surface.
- Erect and branched, up to 2 m tall.
- With spines extending down the stem
from the leaf bases.
- Lanceolate in outline, deeply
lobed, with 3 to 5 white or yellow
spines, 2 to 5 mm long, along the
margins of each lobe,
- Approximately 10 inches long by 4 inches wide.
- The bases extending down to the stem.
- Becoming progressively smaller up the stem.
- Dark green with a waxy surface.
- Without ray florets.
- Usually between 1 and 2 inches wide.
- Often nodding, as the epithet implies.
- Pink to violet or purple.
- With spiny outer phyllaries
often tinted purple, with prominent midvein.
- Blooming from July to August.
- A tan to brown oblong achene.
- About 4 mm long.
- With a white pappus.
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.
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
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.
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
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.
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