Cirsium
A genus of plume thistles with feathered seed hairs.
Cirsium is a genus of flowering plants in the Asteraceae family, comprising both perennial and biennial species. It belongs to a group of plants commonly called thistles, but these are specifically known as plume thistles. What sets them apart from related genera like *Carduus*, *Silybum*, and *Onopordum* is the structure of their seeds: each achene bears a pappus made of feathered hairs, whereas other thistle genera have simple, unbranched hairs on their pappus. Most species are native to Eurasia and northern Africa, with roughly 60 species originating from North America, though several have been introduced beyond their natural ranges. The designated lectotype for the genus is *Cirsium heterophyllum* (L.) Hill. These plants produce showy flower heads, typically in shades of purple, rose, or pink, though yellow and white also occur. The disc flowers are radially symmetrical, arranged at the tips of branches, and attract a wide variety of insects under a generalized pollination system. Stems are erect, and the base of each flower is characteristically enlarged and often spiny. Leaves grow alternately; many species have spiny leaves, but not all, and some have leaves that are slightly to densely hairy. Extensions from the leaf base running down the stem—called wings—can be absent (as in *Cirsium arvense*), conspicuous (as in *Cirsium vulgare*), or inconspicuous. Reproduction occurs via seed and, in some species like *Cirsium arvense*, through underground rhizomes. The seeds are equipped with a tuft of hair (pappus) that allows wind dispersal over long distances. Larvae of various Lepidoptera species feed on *Cirsium* thistles, and the seeds attract small finches, including the American goldfinch. Many species are considered weeds, especially by agricultural interests. In the United States, *Cirsium vulgare* (spear thistle, renamed "bull thistle" as a non-native invasive) is listed as a noxious weed in nine states. Despite this, some species are cultivated in gardens and wildflower plantings for their beauty and for supporting pollinators like bees and butterflies. Even species labeled as weeds can provide these benefits. For example, *Cirsium vulgare* ranked among the top 10 for nectar production in a UK survey by the AgriLand project, supported by the UK Insect Pollinators Initiative. In another British study, it was third in nectar sugar production per floral unit (2323 ± 418 μg). Beyond nectar, it supplies seeds for birds such as the European goldfinch (*Carduelis carduelis*) and supports larvae of the Painted Lady butterfly (*Vanessa cardui*). Other common species include *Cirsium arvense*, *Cirsium palustre*, and *Cirsium oleraceum*. Organizations like the Xerces Society have worked to highlight the ecological benefits of thistles, countering the widespread view of them as unwanted weeds. The monarch butterfly (*Danaus plexippus*), for instance, depends on thistles like tall thistle (*Cirsium altissimum*) as nectar sources during migration. Some prairie and wildflower seed companies in the United States sell bulk seed of native North American thistle species for wildlife habitat restoration, though availability is often limited. Bumblebees particularly value thistles for their high nectar output. Certain *Cirsium* species—including *Cirsium monspessulanum*, *Cirsium pyrenaicum*, and *Cirsium vulgare*—have been traditionally used as food in rural parts of southern Europe. *Cirsium oleraceum* is cultivated as a food source in Japan and India, while *Cirsium setidens* is used as a vegetable in Korean cuisine. The name "Cirsium" comes from the Greek word for thistle, *kirsos*, likely derived from "swollen vein." The flowers bloom from April to August. **Selected species** 493 species are accepted.
- genus
- Cirsium
- family
- Asteraceae
- common_name
- Plume thistles
- native_range
- Eurasia and northern Africa, with about 60 species from North America
- lectotype_species
- Cirsium vulgare (Savi) Ten.
- flowering_period
- April to August
Quick Facts
- Taxon
- Cirsium
- Subdivision
- 383; see text
Facts from the source article.
Lore & Background
Cirsium thistles are known for their effusive flower heads, usually purple, rose or pink, also yellow or white. The radially symmetrical disc flowers are at the end of the branches and are visited by many kinds of insects, featuring a generalised pollination syndrome. They have erect stems, with a characteristic enlarged base of the flower which is often spiny. The leaves are alternate, spiny in many but not all species, and in some species can be slightly to densely hairy. Extensions from the leaf base down the stem, called wings, can be lacking (Cirsium arvense), conspicuous (Cirsium vulgare), or inconspicuous. They can spread by seed, and also by rhizomes below the surface (Cirsium arvense). The seeds have a tuft of hair, or pappus, which can carry them far by wind. Many species are considered weeds, typically by agricultural interests. Cirsium vulgare (spear thistle) is listed in the United States (where as a non-native invasive species it has been renamed 'bull thistle') as a noxious weed in nine states. Some species in particular are cultivated in gardens and wildflower plantings for their aesthetic value and/or to support pollinators such as bees and butterflies. Some species dubbed weeds by various interest groups can also provide these benefits. Cirsium vulgare, for instance, ranked in the top 10 for nectar production in a UK plants survey conducted by the AgriLand project which is supported by the UK Insect Pollinators Initiative. Not only does it provide abundant nectar, it provides seeds for birds, such as the European goldfinch Carduelis carduelis, and supports the larvae of the Painted Lady butterfly Vanessa cardui. Some ecological organizations, such as the Xerces Society, have attempted to raise awareness of the benefits of thistles, to counteract the general agricultural and home garden labeling of thistles as unwanted weeds. The monarch butterfly (Danaus plexippus), for instance, was highlighted as relying upon thistles such as tall thistle (Cirsium altissimum) as nectar sources during its migration. Some prairie and wildflower seed production companies in the United States supply bulk seed of native North American thistle species for wildlife habitat restoration, although availability tends to be low. Thistles are particularly valued by bumblebees for their high nectar production.
Reader's Guide
Cirsium thistles hold significance both as agricultural weeds and as valuable ecological resources. Many species are considered noxious weeds, particularly Cirsium vulgare, which is listed as a noxious weed in nine U.S. states. However, these same plants provide substantial benefits to pollinators and wildlife. Cirsium vulgare ranked in the top 10 for nectar production in a UK survey and was third in nectar sugar production per floral unit in another British study. The seeds attract small finches such as the American goldfinch and European goldfinch, and the larvae of the Painted Lady butterfly feed on the plants. The monarch butterfly relies on thistles like Cirsium altissimum as nectar sources during migration. Organizations such as the Xerces Society have worked to raise awareness of these benefits. Some species are cultivated in gardens and wildflower plantings for aesthetic value and pollinator support. Certain species have been traditionally used as food in southern Europe, Japan, India, and Korea. The name 'Cirsium' is the Greek word for thistle, kirsos, likely derived from 'swollen vein'.
Did You Know?
- Cirsium thistles are distinguished from other thistle genera by having a seed with a pappus of feathered hairs on their achenes.
- Cirsium vulgare ranked in the top 10 for nectar production in a UK plants survey supported by the UK Insect Pollinators Initiative.
- The monarch butterfly relies upon thistles such as tall thistle (Cirsium altissimum) as nectar sources during its migration.
- Cirsium oleraceum is cultivated as a food source in Japan and India, and Cirsium setidens is used as a vegetable in Korean cuisine.
Frequently Asked Questions
Who is Cirsium?
Cirsium is a genus of perennial and biennial flowering plants in the Asteraceae family, commonly grouped with other thistles. It is more precisely called the plume thistles to set it apart from other thistle genera.
What sets Cirsium apart from other thistle genera?
The defining trait is a pappus of feathered hairs attached to each achene (seed). This plume-like structure is what earns the genus its 'plume thistle' common name and separates it from lookalike thistles.
Where is Cirsium native to?
The genus is primarily native to Eurasia and northern Africa, with roughly 60 species occurring in North America. A number of species have also been introduced into regions well outside their original ranges.
What is Cirsium's lectotype species?
The lectotype species designated for the genus is Cirsium vulgare (Savi) Ten. It serves as the fixed reference point for the genus's formal classification.
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