Carnegiea gigantea, Giant Saguaro

Southwest Desert Flora

Home to the plants of the Sonoran, Chihuahuan and Mojave Deserts

Cirsium ochrocentrum, Yellowspine Thistle

Carduus pycnocephalus, Italian Plumeless-Thistle

Italian Plumeless-Thistle has pretty flowers for such an invasive species. Flowers are pink or purple with cylindrical heads that are either solitary or in clusters of 1 to 5 or more. Note upright spines on bracts surrounding the floral head. Carduus pycnocephalusItalian Plumeless-Thistle blooms from March to June or July across its range. Fruits set shortly after the bloom period. These invasive plants may be found in disturbed open sites, roadsides, pastures, annual grasslands, and waste areas. Carduus pycnocephalusItalian Plumeless-Thistle may grow up to 4 feet tall and have multiple stems winged with spines. This species is It is native to the Mediterranean region and some other countries further north or east. Carduus pycnocephalusItalian Plumeless-Thistle is known as a troublesome weedy plant across North American and Europe and goes be other common names such as: Compact-headed Thistle, Italian Plumeless Thistle, Italian Thistle, Plymouth Thistle, Sheep Thistle, Shore Thistle, Slender Thistle, Slender Winged Thistle, Slender-flower Thistle, Winged Slender Thistle, Woolly Thistle. Carduus pycnocephalus

Scientific Name: Carduus pycnocephalus
Common Name: Italian Plumeless-Thistle

Also Called: Compact-headed Thistle, Italian Plumeless Thistle, Italian Thistle, Plymouth Thistle, Sheep Thistle, Shore Thistle, Slender Thistle, Slender Winged Thistle, Slender-flower Thistle, Winged Slender Thistle, Woolly Thistle

Family: Asteraceae, Sunflower Family

Synonyms: ()

Status: Introduced/invasive.

Duration: Annual; winter, sometimes biennial.

Size: 1 to 4 feet (.3-1.2 m) tall.

Growth Form: Forb/herb; stems variable 8 inches to 6.5 feet (20 cm to 2 m), plants glabrous to slightly wooly, multiple stems winged with spines.

Leaves: Green; plants start as rosettes, 4 to 10 lobes basal leaves 4 to 6 inches (10–15 cm) long; stem leaves tomentose on the underside (abaxial) with spines of the lobe tips.

Flower Color: Pink or purple; cylindrical heads, solitary or clusters of 1 or 2 to more than 5; phyllaries persistently tomentose, often matted with cobwebby hairs at the base of the phyllaries and spiny toward tips; corollas pink to purple; fruits color variable across range gray, brown, gold, inner portions yellowish to tan; with bristly minutely barbed pappus.

Flowering Season: March to June or July

Elevation: Below 4,000 feet (1,200 m).

Habitat Preferences: Widely distributed in disturbed open sites, roadsides, pastures, annual grasslands, and waste areas.

Recorded Range: Carduus pycnocephalus is an invasive species in the United States in: AL, AR, CA, ID, NY, OR, SC, TX, WA. It is native to the Mediterranean region and some other countries further north or east.

North America & US County Distribution Map for Carduus pycnocephalus.

U.S. Weed Information: In North America Carduus pycnocephalus, Italian thistle; compact-headed thistle can be weedy or invasive according to the following authoritative sources: State noxious weed lists for 46 states; California Invasive Plant Council; Weeds of the West. Plants included here may become weedy or invasive.

Invasive/Noxious Weed Information: In North America species is listed as a Noxious Weed by the federal government and/or a State; Arkansas, Carduus thistle, Noxious weed; California, Italian thistle C list (noxious weeds); Iowa, Carduus thistle, Primary noxious weed; Oregon, Italian thistle "B" designated weed, Italian thistle, Quarantine; Washington, Italian thistle Class A noxious weed, Italian thistle Noxious weed seed and plant quarantine. Plants included here are invasive or noxious.
Carduus pycnocephalus has become a noxious weed in Australia, New Zealand, Macaronesia, South Africa, the Arabian Peninsula, South America, Hawaii, and North America.

Wetland Indicator: No information available.
Threatened/Endangered Information: No information available.

Genus Information: In North America there are 6 species and 6 accepted taxa overall for Carduus. Worldwide, The Plant List includes 130 accepted species names and a further 297 scientific names of infraspecific rank for Carduus.

In the Southwestern United States: Arizona has 6 species of genus Carduus, California has 10 species, Nevada has 7 species, New Mexico and Utah each have 9 species, Texas has 13 species. All data approximate and subject to revision.

There are 2 sub-species in Carduus pycnocephalus, 1 in the United States;
Carduus pycnocephalus subsp. pycnocephalus.

Comments: Carduus pycnocephalus is introduced in North America and has become an introduced species in other regions around the world, often becoming a noxious weed or invasive species. This species grows densely, crowding out other vegetation and competing with native species. Its ability to grow in dense stands increases the risk of wildfire.

Importance to Wildlife, Birds and Livestock
Carduus pycnocephalus is an invasive species which spreads rapidly and forms dense stands in pastures and rangeland likely crowding out desirable forage for wildlife species and livestock. Additionally, animals do not like to forage on it because its foliage is so spiny. Birds and small mammals including bats may likely feed on the small seeds and what nectar that might be available.

Special Value to Native Bees, Butterflies and Insects
Insects may feed from the florets.

Etymology:
The genus Carduus is the Latin name for "thistle" or "thistle-like plant". The genus Carduus was published by Carl Linnaeus in 1753.
The species epithet "pycnocephalus" means "thick-headed", with heads in thick clusters.

Ethnobotany
Unknown

Date Profile Completed: 02/03/2020
References:
U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database and USGS ITIS search - (accessed 02/03/2020)
https://plants.usda.gov/java/ClassificationServlet?source=profile&symbol=CARDU&display=31
The Plant List (2013). Version 1.1. Published on the Internet; http://www.theplantlist.org/ (accessed 02/03/2020).
http://www.theplantlist.org/1.1/browse/A/Compositae/Carduus/
'Carduus pycnocephalus', Wikipedia, The Free Encyclopedia, 1 December 2019, 01:26 UTC,
https://en.wikipedia.org/w/index.php?title=Carduus_pycnocephalus&oldid=928693322 [accessed 3 February 2020]
Kaylee Tillery, Michasia Harris, Lily Connor, 2013,; National database from the Center for Invasive Species and Ecosystem Health at the University of Georgia; BugwoodWiki; (accessed 02/03/2020)
https://wiki.bugwood.org/Carduus_pycnocephalus
California Invasive Plant Council (CAL-IPC); Carduus pycnocephalus - (accessed 02/03/2020).
https://www.cal-ipc.org/plants/profile/carduus-pycnocephalus-profile/
[original text by Ian Popay], CABI - In: Invasive Species Compendium. Wallingford, UK: CAB International. Carduus pycnocephalus - (accessed 02/03/2020).
www.cabi.org/isc
David J. Keil 2012, Carduus pycnocephalus subsp. pycnocephalus, in Jepson Flora Project (eds.) Jepson eFlora - accessed on February 03, 2020.
https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=82221
David J. Keil,FNA | Family List | FNA Vol. 19, 20 and 21 | Asteraceae | Carduus 4. Carduus pycnocephalus Linnaeus, Sp. Pl. Ed. 2,. 2: 1151. 1763; Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford.
SEINet synonyms, scientific names, geographic locations, general information.
http://swbiodiversity.org/seinet/
Etymology:Michael L. Charters California Plant Names: Latin and Greek Meanings and Derivations; A Dictionary of Botanical and Biographical Etymology - (accessed 02/03/2020)
http://www.calflora.net/botanicalnames/pageCA-CH.html
http://www.calflora.net/botanicalnames/pagePI-PY.html